1 /*
   2  * Copyright (c) 1999, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.util.regex;
  27 
  28 import java.text.Normalizer;
  29 import java.text.Normalizer.Form;
  30 import java.util.Locale;
  31 import java.util.Iterator;
  32 import java.util.Map;
  33 import java.util.ArrayList;
  34 import java.util.HashMap;
  35 import java.util.LinkedHashSet;
  36 import java.util.List;
  37 import java.util.Set;
  38 import java.util.Arrays;
  39 import java.util.NoSuchElementException;
  40 import java.util.Spliterator;
  41 import java.util.Spliterators;
  42 import java.util.function.Predicate;
  43 import java.util.stream.Stream;
  44 import java.util.stream.StreamSupport;
  45 
  46 import jdk.internal.util.ArraysSupport;
  47 
  48 /**
  49  * A compiled representation of a regular expression.
  50  *
  51  * <p> A regular expression, specified as a string, must first be compiled into
  52  * an instance of this class.  The resulting pattern can then be used to create
  53  * a {@link Matcher} object that can match arbitrary {@linkplain
  54  * java.lang.CharSequence character sequences} against the regular
  55  * expression.  All of the state involved in performing a match resides in the
  56  * matcher, so many matchers can share the same pattern.
  57  *
  58  * <p> A typical invocation sequence is thus
  59  *
  60  * <blockquote><pre>
  61  * Pattern p = Pattern.{@link #compile compile}("a*b");
  62  * Matcher m = p.{@link #matcher matcher}("aaaaab");
  63  * boolean b = m.{@link Matcher#matches matches}();</pre></blockquote>
  64  *
  65  * <p> A {@link #matches matches} method is defined by this class as a
  66  * convenience for when a regular expression is used just once.  This method
  67  * compiles an expression and matches an input sequence against it in a single
  68  * invocation.  The statement
  69  *
  70  * <blockquote><pre>
  71  * boolean b = Pattern.matches("a*b", "aaaaab");</pre></blockquote>
  72  *
  73  * is equivalent to the three statements above, though for repeated matches it
  74  * is less efficient since it does not allow the compiled pattern to be reused.
  75  *
  76  * <p> Instances of this class are immutable and are safe for use by multiple
  77  * concurrent threads.  Instances of the {@link Matcher} class are not safe for
  78  * such use.
  79  *
  80  *
  81  * <h2><a id="sum">Summary of regular-expression constructs</a></h2>
  82  *
  83  * <table class="borderless">
  84  * <caption style="display:none">Regular expression constructs, and what they match</caption>
  85  * <thead style="text-align:left">
  86  * <tr>
  87  * <th id="construct">Construct</th>
  88  * <th id="matches">Matches</th>
  89  * </tr>
  90  * </thead>
  91  * <tbody style="text-align:left">
  92  *
  93  * <tr><th colspan="2" style="padding-top:20px" id="characters">Characters</th></tr>
  94  *
  95  * <tr><th style="vertical-align:top; font-weight: normal" id="x"><i>x</i></th>
  96  *     <td headers="matches characters x">The character <i>x</i></td></tr>
  97  * <tr><th style="vertical-align:top; font-weight: normal" id="backslash">{@code \\}</th>
  98  *     <td headers="matches characters backslash">The backslash character</td></tr>
  99  * <tr><th style="vertical-align:top; font-weight: normal" id="octal_n">{@code \0}<i>n</i></th>
 100  *     <td headers="matches characters octal_n">The character with octal value {@code 0}<i>n</i>
 101  *         (0&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;7)</td></tr>
 102  * <tr><th style="vertical-align:top; font-weight: normal" id="octal_nn">{@code \0}<i>nn</i></th>
 103  *     <td headers="matches characters octal_nn">The character with octal value {@code 0}<i>nn</i>
 104  *         (0&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;7)</td></tr>
 105  * <tr><th style="vertical-align:top; font-weight: normal" id="octal_nnn">{@code \0}<i>mnn</i></th>
 106  *     <td headers="matches characters octal_nnn">The character with octal value {@code 0}<i>mnn</i>
 107  *         (0&nbsp;{@code <=}&nbsp;<i>m</i>&nbsp;{@code <=}&nbsp;3,
 108  *         0&nbsp;{@code <=}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;7)</td></tr>
 109  * <tr><th style="vertical-align:top; font-weight: normal" id="hex_hh">{@code \x}<i>hh</i></th>
 110  *     <td headers="matches characters hex_hh">The character with hexadecimal value {@code 0x}<i>hh</i></td></tr>
 111  * <tr><th style="vertical-align:top; font-weight: normal" id="hex_hhhh"><code>\u</code><i>hhhh</i></th>
 112  *     <td headers="matches characters hex_hhhh">The character with hexadecimal&nbsp;value&nbsp;{@code 0x}<i>hhhh</i></td></tr>
 113  * <tr><th style="vertical-align:top; font-weight: normal" id="hex_h_h"><code>\x</code><i>{h...h}</i></th>
 114  *     <td headers="matches characters hex_h_h">The character with hexadecimal value {@code 0x}<i>h...h</i>
 115  *         ({@link java.lang.Character#MIN_CODE_POINT Character.MIN_CODE_POINT}
 116  *         &nbsp;&lt;=&nbsp;{@code 0x}<i>h...h</i>&nbsp;&lt;=&nbsp;
 117  *          {@link java.lang.Character#MAX_CODE_POINT Character.MAX_CODE_POINT})</td></tr>
 118  * <tr><th style="vertical-align:top; font-weight: normal" id="unicode_name"><code>\N{</code><i>name</i><code>}</code></th>
 119  *     <td headers="matches characters unicode_name">The character with Unicode character name <i>'name'</i></td></tr>
 120  * <tr><th style="vertical-align:top; font-weight:normal" id="tab">{@code \t}</th>
 121  *     <td headers="matches characters tab">The tab character (<code>'\u0009'</code>)</td></tr>
 122  * <tr><th style="vertical-align:top; font-weight:normal" id="newline">{@code \n}</th>
 123  *     <td headers="matches characters newline">The newline (line feed) character (<code>'\u000A'</code>)</td></tr>
 124  * <tr><th style="vertical-align:top; font-weight:normal" id="return">{@code \r}</th>
 125  *     <td headers="matches characters return">The carriage-return character (<code>'\u000D'</code>)</td></tr>
 126  * <tr><th style="vertical-align:top; font-weight:normal" id="form_feed">{@code \f}</th>
 127  *     <td headers="matches characters form_feed">The form-feed character (<code>'\u000C'</code>)</td></tr>
 128  * <tr><th style="vertical-align:top; font-weight:normal" id="bell">{@code \a}</th>
 129  *     <td headers="matches characters bell">The alert (bell) character (<code>'\u0007'</code>)</td></tr>
 130  * <tr><th style="vertical-align:top; font-weight:normal" id="escape">{@code \e}</th>
 131  *     <td headers="matches characters escape">The escape character (<code>'\u001B'</code>)</td></tr>
 132  * <tr><th style="vertical-align:top; font-weight:normal" id="ctrl_x">{@code \c}<i>x</i></th>
 133  *     <td headers="matches characters ctrl_x">The control character corresponding to <i>x</i></td></tr>
 134  *
 135  *  <tr><th colspan="2" style="padding-top:20px" id="classes">Character classes</th></tr>
 136  *
 137  * <tr><th style="vertical-align:top; font-weight:normal" id="simple">{@code [abc]}</th>
 138  *     <td headers="matches classes simple">{@code a}, {@code b}, or {@code c} (simple class)</td></tr>
 139  * <tr><th style="vertical-align:top; font-weight:normal" id="negation">{@code [^abc]}</th>
 140  *     <td headers="matches classes negation">Any character except {@code a}, {@code b}, or {@code c} (negation)</td></tr>
 141  * <tr><th style="vertical-align:top; font-weight:normal" id="range">{@code [a-zA-Z]}</th>
 142  *     <td headers="matches classes range">{@code a} through {@code z}
 143  *         or {@code A} through {@code Z}, inclusive (range)</td></tr>
 144  * <tr><th style="vertical-align:top; font-weight:normal" id="union">{@code [a-d[m-p]]}</th>
 145  *     <td headers="matches classes union">{@code a} through {@code d},
 146  *      or {@code m} through {@code p}: {@code [a-dm-p]} (union)</td></tr>
 147  * <tr><th style="vertical-align:top; font-weight:normal" id="intersection">{@code [a-z&&[def]]}</th>
 148  *     <td headers="matches classes intersection">{@code d}, {@code e}, or {@code f} (intersection)</tr>
 149  * <tr><th style="vertical-align:top; font-weight:normal" id="subtraction1">{@code [a-z&&[^bc]]}</th>
 150  *     <td headers="matches classes subtraction1">{@code a} through {@code z},
 151  *         except for {@code b} and {@code c}: {@code [ad-z]} (subtraction)</td></tr>
 152  * <tr><th style="vertical-align:top; font-weight:normal" id="subtraction2">{@code [a-z&&[^m-p]]}</th>
 153  *     <td headers="matches classes subtraction2">{@code a} through {@code z},
 154  *          and not {@code m} through {@code p}: {@code [a-lq-z]}(subtraction)</td></tr>
 155  *
 156  * <tr><th colspan="2" style="padding-top:20px" id="predef">Predefined character classes</th></tr>
 157  *
 158  * <tr><th style="vertical-align:top; font-weight:normal" id="any">{@code .}</th>
 159  *     <td headers="matches predef any">Any character (may or may not match <a href="#lt">line terminators</a>)</td></tr>
 160  * <tr><th style="vertical-align:top; font-weight:normal" id="digit">{@code \d}</th>
 161  *     <td headers="matches predef digit">A digit: {@code [0-9]}</td></tr>
 162  * <tr><th style="vertical-align:top; font-weight:normal" id="non_digit">{@code \D}</th>
 163  *     <td headers="matches predef non_digit">A non-digit: {@code [^0-9]}</td></tr>
 164  * <tr><th style="vertical-align:top; font-weight:normal" id="horiz_white">{@code \h}</th>
 165  *     <td headers="matches predef horiz_white">A horizontal whitespace character:
 166  *     <code>[ \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000]</code></td></tr>
 167  * <tr><th style="vertical-align:top; font-weight:normal" id="non_horiz_white">{@code \H}</th>
 168  *     <td headers="matches predef non_horiz_white">A non-horizontal whitespace character: {@code [^\h]}</td></tr>
 169  * <tr><th style="vertical-align:top; font-weight:normal" id="white">{@code \s}</th>
 170  *     <td headers="matches predef white">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
 171  * <tr><th style="vertical-align:top; font-weight:normal" id="non_white">{@code \S}</th>
 172  *     <td headers="matches predef non_white">A non-whitespace character: {@code [^\s]}</td></tr>
 173  * <tr><th style="vertical-align:top; font-weight:normal" id="vert_white">{@code \v}</th>
 174  *     <td headers="matches predef vert_white">A vertical whitespace character: <code>[\n\x0B\f\r\x85\u2028\u2029]</code>
 175  *     </td></tr>
 176  * <tr><th style="vertical-align:top; font-weight:normal" id="non_vert_white">{@code \V}</th>
 177  *     <td headers="matches predef non_vert_white">A non-vertical whitespace character: {@code [^\v]}</td></tr>
 178  * <tr><th style="vertical-align:top; font-weight:normal" id="word">{@code \w}</th>
 179  *     <td headers="matches predef word">A word character: {@code [a-zA-Z_0-9]}</td></tr>
 180  * <tr><th style="vertical-align:top; font-weight:normal" id="non_word">{@code \W}</th>
 181  *     <td headers="matches predef non_word">A non-word character: {@code [^\w]}</td></tr>
 182  *
 183  * <tr><th colspan="2" style="padding-top:20px" id="posix"><b>POSIX character classes (US-ASCII only)</b></th></tr>
 184  *
 185  * <tr><th style="vertical-align:top; font-weight:normal" id="Lower">{@code \p{Lower}}</th>
 186  *     <td headers="matches posix Lower">A lower-case alphabetic character: {@code [a-z]}</td></tr>
 187  * <tr><th style="vertical-align:top; font-weight:normal" id="Upper">{@code \p{Upper}}</th>
 188  *     <td headers="matches posix Upper">An upper-case alphabetic character:{@code [A-Z]}</td></tr>
 189  * <tr><th style="vertical-align:top; font-weight:normal" id="ASCII">{@code \p{ASCII}}</th>
 190  *     <td headers="matches posix ASCII">All ASCII:{@code [\x00-\x7F]}</td></tr>
 191  * <tr><th style="vertical-align:top; font-weight:normal" id="Alpha">{@code \p{Alpha}}</th>
 192  *     <td headers="matches posix Alpha">An alphabetic character:{@code [\p{Lower}\p{Upper}]}</td></tr>
 193  * <tr><th style="vertical-align:top; font-weight:normal" id="Digit">{@code \p{Digit}}</th>
 194  *     <td headers="matches posix Digit">A decimal digit: {@code [0-9]}</td></tr>
 195  * <tr><th style="vertical-align:top; font-weight:normal" id="Alnum">{@code \p{Alnum}}</th>
 196  *     <td headers="matches posix Alnum">An alphanumeric character:{@code [\p{Alpha}\p{Digit}]}</td></tr>
 197  * <tr><th style="vertical-align:top; font-weight:normal" id="Punct">{@code \p{Punct}}</th>
 198  *     <td headers="matches posix Punct">Punctuation: One of {@code !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~}</td></tr>
 199  *     <!-- {@code [\!"#\$%&'\(\)\*\+,\-\./:;\<=\>\?@\[\\\]\^_`\{\|\}~]}
 200  *          {@code [\X21-\X2F\X31-\X40\X5B-\X60\X7B-\X7E]} -->
 201  * <tr><th style="vertical-align:top; font-weight:normal" id="Graph">{@code \p{Graph}}</th>
 202  *     <td headers="matches posix Graph">A visible character: {@code [\p{Alnum}\p{Punct}]}</td></tr>
 203  * <tr><th style="vertical-align:top; font-weight:normal" id="Print">{@code \p{Print}}</th>
 204  *     <td headers="matches posix Print">A printable character: {@code [\p{Graph}\x20]}</td></tr>
 205  * <tr><th style="vertical-align:top; font-weight:normal" id="Blank">{@code \p{Blank}}</th>
 206  *     <td headers="matches posix Blank">A space or a tab: {@code [ \t]}</td></tr>
 207  * <tr><th style="vertical-align:top; font-weight:normal" id="Cntrl">{@code \p{Cntrl}}</th>
 208  *     <td headers="matches posix Cntrl">A control character: {@code [\x00-\x1F\x7F]}</td></tr>
 209  * <tr><th style="vertical-align:top; font-weight:normal" id="XDigit">{@code \p{XDigit}}</th>
 210  *     <td headers="matches posix XDigit">A hexadecimal digit: {@code [0-9a-fA-F]}</td></tr>
 211  * <tr><th style="vertical-align:top; font-weight:normal" id="Space">{@code \p{Space}}</th>
 212  *     <td headers="matches posix Space">A whitespace character: {@code [ \t\n\x0B\f\r]}</td></tr>
 213  *
 214  * <tr><th colspan="2" style="padding-top:20px" id="java">java.lang.Character classes (simple <a href="#jcc">java character type</a>)</th></tr>
 215  *
 216  * <tr><th style="vertical-align:top; font-weight:normal" id="javaLowerCase">{@code \p{javaLowerCase}}</th>
 217  *     <td headers="matches java javaLowerCase">Equivalent to java.lang.Character.isLowerCase()</td></tr>
 218  * <tr><th style="vertical-align:top; font-weight:normal" id="javaUpperCase">{@code \p{javaUpperCase}}</th>
 219  *     <td headers="matches java javaUpperCase">Equivalent to java.lang.Character.isUpperCase()</td></tr>
 220  * <tr><th style="vertical-align:top; font-weight:normal" id="javaWhitespace">{@code \p{javaWhitespace}}</th>
 221  *     <td headers="matches java javaWhitespace">Equivalent to java.lang.Character.isWhitespace()</td></tr>
 222  * <tr><th style="vertical-align:top; font-weight:normal" id="javaMirrored">{@code \p{javaMirrored}}</th>
 223  *     <td headers="matches java javaMirrored">Equivalent to java.lang.Character.isMirrored()</td></tr>
 224  *
 225  * <tr><th colspan="2" style="padding-top:20px"  id="unicode">Classes for Unicode scripts, blocks, categories and binary properties</th></tr>
 226  *
 227  * <tr><th style="vertical-align:top; font-weight:normal" id="IsLatin">{@code \p{IsLatin}}</th>
 228  *     <td headers="matches unicode IsLatin">A Latin&nbsp;script character (<a href="#usc">script</a>)</td></tr>
 229  * <tr><th style="vertical-align:top; font-weight:normal" id="InGreek">{@code \p{InGreek}}</th>
 230  *     <td headers="matches unicode InGreek">A character in the Greek&nbsp;block (<a href="#ubc">block</a>)</td></tr>
 231  * <tr><th style="vertical-align:top; font-weight:normal" id="Lu">{@code \p{Lu}}</th>
 232  *     <td headers="matches unicode Lu">An uppercase letter (<a href="#ucc">category</a>)</td></tr>
 233  * <tr><th style="vertical-align:top; font-weight:normal" id="IsAlphabetic">{@code \p{IsAlphabetic}}</th>
 234  *     <td headers="matches unicode IsAlphabetic">An alphabetic character (<a href="#ubpc">binary property</a>)</td></tr>
 235  * <tr><th style="vertical-align:top; font-weight:normal" id="Sc">{@code \p{Sc}}</th>
 236  *     <td headers="matches unicode Sc">A currency symbol</td></tr>
 237  * <tr><th style="vertical-align:top; font-weight:normal" id="not_InGreek">{@code \P{InGreek}}</th>
 238  *     <td headers="matches unicode not_InGreek">Any character except one in the Greek block (negation)</td></tr>
 239  * <tr><th style="vertical-align:top; font-weight:normal" id="not_uppercase">{@code [\p{L}&&[^\p{Lu}]]}</th>
 240  *     <td headers="matches unicode not_uppercase">Any letter except an uppercase letter (subtraction)</td></tr>
 241  *
 242  * <tr><th colspan="2" style="padding-top:20px" id="bounds">Boundary matchers</th></tr>
 243  *
 244  * <tr><th style="vertical-align:top; font-weight:normal" id="begin_line">{@code ^}</th>
 245  *     <td headers="matches bounds begin_line">The beginning of a line</td></tr>
 246  * <tr><th style="vertical-align:top; font-weight:normal" id="end_line">{@code $}</th>
 247  *     <td headers="matches bounds end_line">The end of a line</td></tr>
 248  * <tr><th style="vertical-align:top; font-weight:normal" id="word_boundary">{@code \b}</th>
 249  *     <td headers="matches bounds word_boundary">A word boundary</td></tr>
 250  * <tr><th style="vertical-align:top; font-weight:normal" id="grapheme_cluster_boundary">{@code \b{g}}</th>
 251  *     <td headers="matches bounds grapheme_cluster_boundary">A Unicode extended grapheme cluster boundary</td></tr>
 252  * <tr><th style="vertical-align:top; font-weight:normal" id="non_word_boundary">{@code \B}</th>
 253  *     <td headers="matches bounds non_word_boundary">A non-word boundary</td></tr>
 254  * <tr><th style="vertical-align:top; font-weight:normal" id="begin_input">{@code \A}</th>
 255  *     <td headers="matches bounds begin_input">The beginning of the input</td></tr>
 256  * <tr><th style="vertical-align:top; font-weight:normal" id="end_prev_match">{@code \G}</th>
 257  *     <td headers="matches bounds end_prev_match">The end of the previous match</td></tr>
 258  * <tr><th style="vertical-align:top; font-weight:normal" id="end_input_except_term">{@code \Z}</th>
 259  *     <td headers="matches bounds end_input_except_term">The end of the input but for the final
 260  *         <a href="#lt">terminator</a>, if&nbsp;any</td></tr>
 261  * <tr><th style="vertical-align:top; font-weight:normal" id="end_input">{@code \z}</th>
 262  *     <td headers="matches bounds end_input">The end of the input</td></tr>
 263  *
 264  * <tr><th colspan="2" style="padding-top:20px" id="linebreak">Linebreak matcher</th></tr>
 265  *
 266  * <tr><th style="vertical-align:top; font-weight:normal" id="any_unicode_linebreak">{@code \R}</th>
 267  *     <td headers="matches linebreak any_unicode_linebreak">Any Unicode linebreak sequence, is equivalent to
 268  *     <code>\u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
 269  *     </code></td></tr>
 270  *
 271  * <tr><th colspan="2" style="padding-top:20px" id="grapheme">Unicode Extended Grapheme matcher</th></tr>
 272  *
 273  * <tr><th style="vertical-align:top; font-weight:normal" id="grapheme_any">{@code \X}</th>
 274  *     <td headers="matches grapheme grapheme_any">Any Unicode extended grapheme cluster</td></tr>
 275  *
 276  * <tr><th colspan="2" style="padding-top:20px" id="greedy">Greedy quantifiers</th></tr>
 277  *
 278  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_once_or_not"><i>X</i>{@code ?}</th>
 279  *     <td headers="matches greedy greedy_once_or_not"><i>X</i>, once or not at all</td></tr>
 280  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_zero_or_more"><i>X</i>{@code *}</th>
 281  *     <td headers="matches greedy greedy_zero_or_more"><i>X</i>, zero or more times</td></tr>
 282  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_one_or_more"><i>X</i>{@code +}</th>
 283  *     <td headers="matches greedy greedy_one_or_more"><i>X</i>, one or more times</td></tr>
 284  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_exactly"><i>X</i><code>{</code><i>n</i><code>}</code></th>
 285  *     <td headers="matches greedy greedy_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
 286  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_at_least"><i>X</i><code>{</code><i>n</i>{@code ,}}</th>
 287  *     <td headers="matches greedy greedy_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
 288  * <tr><th style="vertical-align:top; font-weight:normal" id="greedy_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}</code></th>
 289  *     <td headers="matches greedy greedy_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 290  *
 291  * <tr><th colspan="2" style="padding-top:20px" id="reluc">Reluctant quantifiers</th></tr>
 292  *
 293  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_once_or_not"><i>X</i>{@code ??}</th>
 294  *     <td headers="matches reluc reluc_once_or_not"><i>X</i>, once or not at all</td></tr>
 295  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_zero_or_more"><i>X</i>{@code *?}</th>
 296  *     <td headers="matches reluc reluc_zero_or_more"><i>X</i>, zero or more times</td></tr>
 297  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_one_or_more"><i>X</i>{@code +?}</th>
 298  *     <td headers="matches reluc reluc_one_or_more"><i>X</i>, one or more times</td></tr>
 299  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_exactly"><i>X</i><code>{</code><i>n</i><code>}?</code></th>
 300  *     <td headers="matches reluc reluc_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
 301  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_at_least"><i>X</i><code>{</code><i>n</i><code>,}?</code></th>
 302  *     <td headers="matches reluc reluc_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
 303  * <tr><th style="vertical-align:top; font-weight:normal" id="reluc_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}?</code></th>
 304  *     <td headers="matches reluc reluc_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 305  *
 306  * <tr><th colspan="2" style="padding-top:20px" id="poss">Possessive quantifiers</th></tr>
 307  *
 308  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_once_or_not"><i>X</i>{@code ?+}</th>
 309  *     <td headers="matches poss poss_once_or_not"><i>X</i>, once or not at all</td></tr>
 310  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_zero_or_more"><i>X</i>{@code *+}</th>
 311  *     <td headers="matches poss poss_zero_or_more"><i>X</i>, zero or more times</td></tr>
 312  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_one_or_more"><i>X</i>{@code ++}</th>
 313  *     <td headers="matches poss poss_one_or_more"><i>X</i>, one or more times</td></tr>
 314  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_exactly"><i>X</i><code>{</code><i>n</i><code>}+</code></th>
 315  *     <td headers="matches poss poss_exactly"><i>X</i>, exactly <i>n</i> times</td></tr>
 316  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_at_least"><i>X</i><code>{</code><i>n</i><code>,}+</code></th>
 317  *     <td headers="matches poss poss_at_least"><i>X</i>, at least <i>n</i> times</td></tr>
 318  * <tr><th style="vertical-align:top; font-weight:normal" id="poss_at_least_up_to"><i>X</i><code>{</code><i>n</i>{@code ,}<i>m</i><code>}+</code></th>
 319  *     <td headers="matches poss poss_at_least_up_to"><i>X</i>, at least <i>n</i> but not more than <i>m</i> times</td></tr>
 320  *
 321  * <tr><th colspan="2" style="padding-top:20px" id="logical">Logical operators</th></tr>
 322  *
 323  * <tr><th style="vertical-align:top; font-weight:normal" id="concat"><i>XY</i></th>
 324  *     <td headers="matches logical concat"><i>X</i> followed by <i>Y</i></td></tr>
 325  * <tr><th style="vertical-align:top; font-weight:normal" id="alternate"><i>X</i>{@code |}<i>Y</i></th>
 326  *     <td headers="matches logical alternate">Either <i>X</i> or <i>Y</i></td></tr>
 327  * <tr><th style="vertical-align:top; font-weight:normal" id="group">{@code (}<i>X</i>{@code )}</th>
 328  *     <td headers="matches logical group">X, as a <a href="#cg">capturing group</a></td></tr>
 329  *
 330  * <tr><th colspan="2" style="padding-top:20px" id="backref">Back references</th></tr>
 331  *
 332  * <tr><th style="vertical-align:top; font-weight:normal" id="back_nth">{@code \}<i>n</i></th>
 333  *     <td headers="matches backref back_nth">Whatever the <i>n</i><sup>th</sup>
 334  *     <a href="#cg">capturing group</a> matched</td></tr>
 335  * <tr><th style="vertical-align:top; font-weight:normal" id="back_named">{@code \}<i>k</i>&lt;<i>name</i>&gt;</th>
 336  *     <td headers="matches backref back_named">Whatever the
 337  *     <a href="#groupname">named-capturing group</a> "name" matched</td></tr>
 338  *
 339  * <tr><th colspan="2" style="padding-top:20px" id="quote">Quotation</th></tr>
 340  *
 341  * <tr><th style="vertical-align:top; font-weight:normal" id="quote_follow">{@code \}</th>
 342  *     <td headers="matches quote quote_follow">Nothing, but quotes the following character</td></tr>
 343  * <tr><th style="vertical-align:top; font-weight:normal" id="quote_begin">{@code \Q}</th>
 344  *     <td headers="matches quote quote_begin">Nothing, but quotes all characters until {@code \E}</td></tr>
 345  * <tr><th style="vertical-align:top; font-weight:normal" id="quote_end">{@code \E}</th>
 346  *     <td headers="matches quote quote_end">Nothing, but ends quoting started by {@code \Q}</td></tr>
 347  *     <!-- Metachars: !$()*+.<>?[\]^{|} -->
 348  *
 349  * <tr><th colspan="2" style="padding-top:20px" id="special">Special constructs (named-capturing and non-capturing)</th></tr>
 350  *
 351  * <tr><th style="vertical-align:top; font-weight:normal" id="named_group"><code>(?&lt;<a href="#groupname">name</a>&gt;</code><i>X</i>{@code )}</th>
 352  *     <td headers="matches special named_group"><i>X</i>, as a named-capturing group</td></tr>
 353  * <tr><th style="vertical-align:top; font-weight:normal" id="non_capture_group">{@code (?:}<i>X</i>{@code )}</th>
 354  *     <td headers="matches special non_capture_group"><i>X</i>, as a non-capturing group</td></tr>
 355  * <tr><th style="vertical-align:top; font-weight:normal" id="flags"><code>(?idmsuxU-idmsuxU)&nbsp;</code></th>
 356  *     <td headers="matches special flags">Nothing, but turns match flags <a href="#CASE_INSENSITIVE">i</a>
 357  * <a href="#UNIX_LINES">d</a> <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a>
 358  * <a href="#UNICODE_CASE">u</a> <a href="#COMMENTS">x</a> <a href="#UNICODE_CHARACTER_CLASS">U</a>
 359  * on - off</td></tr>
 360  * <tr><th style="vertical-align:top; font-weight:normal" id="non_capture_group_flags"><code>(?idmsux-idmsux:</code><i>X</i>{@code )}&nbsp;&nbsp;</th>
 361  *     <td headers="matches special non_capture_group_flags"><i>X</i>, as a <a href="#cg">non-capturing group</a> with the
 362  *         given flags <a href="#CASE_INSENSITIVE">i</a> <a href="#UNIX_LINES">d</a>
 363  * <a href="#MULTILINE">m</a> <a href="#DOTALL">s</a> <a href="#UNICODE_CASE">u</a >
 364  * <a href="#COMMENTS">x</a> on - off</td></tr>
 365  * <tr><th style="vertical-align:top; font-weight:normal" id="pos_lookahead">{@code (?=}<i>X</i>{@code )}</th>
 366  *     <td headers="matches special pos_lookahead"><i>X</i>, via zero-width positive lookahead</td></tr>
 367  * <tr><th style="vertical-align:top; font-weight:normal" id="neg_lookahead">{@code (?!}<i>X</i>{@code )}</th>
 368  *     <td headers="matches special neg_lookahead"><i>X</i>, via zero-width negative lookahead</td></tr>
 369  * <tr><th style="vertical-align:top; font-weight:normal" id="pos_lookbehind">{@code (?<=}<i>X</i>{@code )}</th>
 370  *     <td headers="matches special pos_lookbehind"><i>X</i>, via zero-width positive lookbehind</td></tr>
 371  * <tr><th style="vertical-align:top; font-weight:normal" id="neg_lookbehind">{@code (?<!}<i>X</i>{@code )}</th>
 372  *     <td headers="matches special neg_lookbehind"><i>X</i>, via zero-width negative lookbehind</td></tr>
 373  * <tr><th style="vertical-align:top; font-weight:normal" id="indep_non_capture_group">{@code (?>}<i>X</i>{@code )}</th>
 374  *     <td headers="matches special indep_non_capture_group"><i>X</i>, as an independent, non-capturing group</td></tr>
 375  *
 376  * </tbody>
 377  * </table>
 378  *
 379  * <hr>
 380  *
 381  *
 382  * <h2><a id="bs">Backslashes, escapes, and quoting</a></h2>
 383  *
 384  * <p> The backslash character ({@code '\'}) serves to introduce escaped
 385  * constructs, as defined in the table above, as well as to quote characters
 386  * that otherwise would be interpreted as unescaped constructs.  Thus the
 387  * expression {@code \\} matches a single backslash and <code>\{</code> matches a
 388  * left brace.
 389  *
 390  * <p> It is an error to use a backslash prior to any alphabetic character that
 391  * does not denote an escaped construct; these are reserved for future
 392  * extensions to the regular-expression language.  A backslash may be used
 393  * prior to a non-alphabetic character regardless of whether that character is
 394  * part of an unescaped construct.
 395  *
 396  * <p> Backslashes within string literals in Java source code are interpreted
 397  * as required by
 398  * <cite>The Java&trade; Language Specification</cite>
 399  * as either Unicode escapes (section 3.3) or other character escapes (section 3.10.6)
 400  * It is therefore necessary to double backslashes in string
 401  * literals that represent regular expressions to protect them from
 402  * interpretation by the Java bytecode compiler.  The string literal
 403  * <code>"\b"</code>, for example, matches a single backspace character when
 404  * interpreted as a regular expression, while {@code "\\b"} matches a
 405  * word boundary.  The string literal {@code "\(hello\)"} is illegal
 406  * and leads to a compile-time error; in order to match the string
 407  * {@code (hello)} the string literal {@code "\\(hello\\)"}
 408  * must be used.
 409  *
 410  * <h2><a id="cc">Character Classes</a></h2>
 411  *
 412  *    <p> Character classes may appear within other character classes, and
 413  *    may be composed by the union operator (implicit) and the intersection
 414  *    operator ({@code &&}).
 415  *    The union operator denotes a class that contains every character that is
 416  *    in at least one of its operand classes.  The intersection operator
 417  *    denotes a class that contains every character that is in both of its
 418  *    operand classes.
 419  *
 420  *    <p> The precedence of character-class operators is as follows, from
 421  *    highest to lowest:
 422  *
 423  *    <table class="striped" style="margin-left: 2em;">
 424  *      <caption style="display:none">Precedence of character class operators.</caption>
 425  *      <thead>
 426  *      <tr><th scope="col">Precedence<th scope="col">Name<th scope="col">Example
 427  *      </thead>
 428  *      <tbody>
 429  *      <tr><th scope="row">1</th>
 430  *        <td>Literal escape&nbsp;&nbsp;&nbsp;&nbsp;</td>
 431  *        <td>{@code \x}</td></tr>
 432  *     <tr><th scope="row">2</th>
 433  *        <td>Grouping</td>
 434  *        <td>{@code [...]}</td></tr>
 435  *     <tr><th scope="row">3</th>
 436  *        <td>Range</td>
 437  *        <td>{@code a-z}</td></tr>
 438  *      <tr><th scope="row">4</th>
 439  *        <td>Union</td>
 440  *        <td>{@code [a-e][i-u]}</td></tr>
 441  *      <tr><th scope="row">5</th>
 442  *        <td>Intersection</td>
 443  *        <td>{@code [a-z&&[aeiou]]}</td></tr>
 444  *      </tbody>
 445  *    </table>
 446  *
 447  *    <p> Note that a different set of metacharacters are in effect inside
 448  *    a character class than outside a character class. For instance, the
 449  *    regular expression {@code .} loses its special meaning inside a
 450  *    character class, while the expression {@code -} becomes a range
 451  *    forming metacharacter.
 452  *
 453  * <h2><a id="lt">Line terminators</a></h2>
 454  *
 455  * <p> A <i>line terminator</i> is a one- or two-character sequence that marks
 456  * the end of a line of the input character sequence.  The following are
 457  * recognized as line terminators:
 458  *
 459  * <ul>
 460  *
 461  *   <li> A newline (line feed) character ({@code '\n'}),
 462  *
 463  *   <li> A carriage-return character followed immediately by a newline
 464  *   character ({@code "\r\n"}),
 465  *
 466  *   <li> A standalone carriage-return character ({@code '\r'}),
 467  *
 468  *   <li> A next-line character (<code>'\u0085'</code>),
 469  *
 470  *   <li> A line-separator character (<code>'\u2028'</code>), or
 471  *
 472  *   <li> A paragraph-separator character (<code>'\u2029'</code>).
 473  *
 474  * </ul>
 475  * <p>If {@link #UNIX_LINES} mode is activated, then the only line terminators
 476  * recognized are newline characters.
 477  *
 478  * <p> The regular expression {@code .} matches any character except a line
 479  * terminator unless the {@link #DOTALL} flag is specified.
 480  *
 481  * <p> By default, the regular expressions {@code ^} and {@code $} ignore
 482  * line terminators and only match at the beginning and the end, respectively,
 483  * of the entire input sequence. If {@link #MULTILINE} mode is activated then
 484  * {@code ^} matches at the beginning of input and after any line terminator
 485  * except at the end of input. When in {@link #MULTILINE} mode {@code $}
 486  * matches just before a line terminator or the end of the input sequence.
 487  *
 488  * <h2><a id="cg">Groups and capturing</a></h2>
 489  *
 490  * <h3><a id="gnumber">Group number</a></h3>
 491  * <p> Capturing groups are numbered by counting their opening parentheses from
 492  * left to right.  In the expression {@code ((A)(B(C)))}, for example, there
 493  * are four such groups: </p>
 494  *
 495  * <ol style="margin-left:2em;">
 496  *   <li> {@code ((A)(B(C)))}
 497  *   <li> {@code (A)}
 498  *   <li> {@code (B(C))}
 499  *   <li> {@code (C)}
 500  * </ol>
 501  *
 502  * <p> Group zero always stands for the entire expression.
 503  *
 504  * <p> Capturing groups are so named because, during a match, each subsequence
 505  * of the input sequence that matches such a group is saved.  The captured
 506  * subsequence may be used later in the expression, via a back reference, and
 507  * may also be retrieved from the matcher once the match operation is complete.
 508  *
 509  * <h3><a id="groupname">Group name</a></h3>
 510  * <p>A capturing group can also be assigned a "name", a {@code named-capturing group},
 511  * and then be back-referenced later by the "name". Group names are composed of
 512  * the following characters. The first character must be a {@code letter}.
 513  *
 514  * <ul>
 515  *   <li> The uppercase letters {@code 'A'} through {@code 'Z'}
 516  *        (<code>'\u0041'</code>&nbsp;through&nbsp;<code>'\u005a'</code>),
 517  *   <li> The lowercase letters {@code 'a'} through {@code 'z'}
 518  *        (<code>'\u0061'</code>&nbsp;through&nbsp;<code>'\u007a'</code>),
 519  *   <li> The digits {@code '0'} through {@code '9'}
 520  *        (<code>'\u0030'</code>&nbsp;through&nbsp;<code>'\u0039'</code>),
 521  * </ul>
 522  *
 523  * <p> A {@code named-capturing group} is still numbered as described in
 524  * <a href="#gnumber">Group number</a>.
 525  *
 526  * <p> The captured input associated with a group is always the subsequence
 527  * that the group most recently matched.  If a group is evaluated a second time
 528  * because of quantification then its previously-captured value, if any, will
 529  * be retained if the second evaluation fails.  Matching the string
 530  * {@code "aba"} against the expression {@code (a(b)?)+}, for example, leaves
 531  * group two set to {@code "b"}.  All captured input is discarded at the
 532  * beginning of each match.
 533  *
 534  * <p> Groups beginning with {@code (?} are either pure, <i>non-capturing</i> groups
 535  * that do not capture text and do not count towards the group total, or
 536  * <i>named-capturing</i> group.
 537  *
 538  * <h2> Unicode support </h2>
 539  *
 540  * <p> This class is in conformance with Level 1 of <a
 541  * href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
 542  * Standard #18: Unicode Regular Expression</i></a>, plus RL2.1
 543  * Canonical Equivalents and RL2.2 Extended Grapheme Clusters.
 544  * <p>
 545  * <b>Unicode escape sequences</b> such as <code>\u2014</code> in Java source code
 546  * are processed as described in section 3.3 of
 547  * <cite>The Java&trade; Language Specification</cite>.
 548  * Such escape sequences are also implemented directly by the regular-expression
 549  * parser so that Unicode escapes can be used in expressions that are read from
 550  * files or from the keyboard.  Thus the strings <code>"\u2014"</code> and
 551  * {@code "\\u2014"}, while not equal, compile into the same pattern, which
 552  * matches the character with hexadecimal value {@code 0x2014}.
 553  * <p>
 554  * A Unicode character can also be represented by using its <b>Hex notation</b>
 555  * (hexadecimal code point value) directly as described in construct
 556  * <code>\x{...}</code>, for example a supplementary character U+2011F can be
 557  * specified as <code>\x{2011F}</code>, instead of two consecutive Unicode escape
 558  * sequences of the surrogate pair <code>\uD840</code><code>\uDD1F</code>.
 559  * <p>
 560  * <b>Unicode character names</b> are supported by the named character construct
 561  * <code>\N{</code>...<code>}</code>, for example, <code>\N{WHITE SMILING FACE}</code>
 562  * specifies character <code>\u263A</code>. The character names supported
 563  * by this class are the valid Unicode character names matched by
 564  * {@link java.lang.Character#codePointOf(String) Character.codePointOf(name)}.
 565  * <p>
 566  * <a href="http://www.unicode.org/reports/tr18/#Default_Grapheme_Clusters">
 567  * <b>Unicode extended grapheme clusters</b></a> are supported by the grapheme
 568  * cluster matcher {@code \X} and the corresponding boundary matcher {@code \b{g}}.
 569  * <p>
 570  * Unicode scripts, blocks, categories and binary properties are written with
 571  * the {@code \p} and {@code \P} constructs as in Perl.
 572  * <code>\p{</code><i>prop</i><code>}</code> matches if
 573  * the input has the property <i>prop</i>, while <code>\P{</code><i>prop</i><code>}</code>
 574  * does not match if the input has that property.
 575  * <p>
 576  * Scripts, blocks, categories and binary properties can be used both inside
 577  * and outside of a character class.
 578  *
 579  * <p>
 580  * <b><a id="usc">Scripts</a></b> are specified either with the prefix {@code Is}, as in
 581  * {@code IsHiragana}, or by using  the {@code script} keyword (or its short
 582  * form {@code sc}) as in {@code script=Hiragana} or {@code sc=Hiragana}.
 583  * <p>
 584  * The script names supported by {@code Pattern} are the valid script names
 585  * accepted and defined by
 586  * {@link java.lang.Character.UnicodeScript#forName(String) UnicodeScript.forName}.
 587  *
 588  * <p>
 589  * <b><a id="ubc">Blocks</a></b> are specified with the prefix {@code In}, as in
 590  * {@code InMongolian}, or by using the keyword {@code block} (or its short
 591  * form {@code blk}) as in {@code block=Mongolian} or {@code blk=Mongolian}.
 592  * <p>
 593  * The block names supported by {@code Pattern} are the valid block names
 594  * accepted and defined by
 595  * {@link java.lang.Character.UnicodeBlock#forName(String) UnicodeBlock.forName}.
 596  * <p>
 597  *
 598  * <b><a id="ucc">Categories</a></b> may be specified with the optional prefix {@code Is}:
 599  * Both {@code \p{L}} and {@code \p{IsL}} denote the category of Unicode
 600  * letters. Same as scripts and blocks, categories can also be specified
 601  * by using the keyword {@code general_category} (or its short form
 602  * {@code gc}) as in {@code general_category=Lu} or {@code gc=Lu}.
 603  * <p>
 604  * The supported categories are those of
 605  * <a href="http://www.unicode.org/unicode/standard/standard.html">
 606  * <i>The Unicode Standard</i></a> in the version specified by the
 607  * {@link java.lang.Character Character} class. The category names are those
 608  * defined in the Standard, both normative and informative.
 609  * <p>
 610  *
 611  * <b><a id="ubpc">Binary properties</a></b> are specified with the prefix {@code Is}, as in
 612  * {@code IsAlphabetic}. The supported binary properties by {@code Pattern}
 613  * are
 614  * <ul>
 615  *   <li> Alphabetic
 616  *   <li> Ideographic
 617  *   <li> Letter
 618  *   <li> Lowercase
 619  *   <li> Uppercase
 620  *   <li> Titlecase
 621  *   <li> Punctuation
 622  *   <Li> Control
 623  *   <li> White_Space
 624  *   <li> Digit
 625  *   <li> Hex_Digit
 626  *   <li> Join_Control
 627  *   <li> Noncharacter_Code_Point
 628  *   <li> Assigned
 629  * </ul>
 630  * <p>
 631  * The following <b>Predefined Character classes</b> and <b>POSIX character classes</b>
 632  * are in conformance with the recommendation of <i>Annex C: Compatibility Properties</i>
 633  * of <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Regular Expression
 634  * </i></a>, when {@link #UNICODE_CHARACTER_CLASS} flag is specified.
 635  *
 636  * <table class="striped">
 637  * <caption style="display:none">predefined and posix character classes in Unicode mode</caption>
 638  * <thead>
 639  * <tr>
 640  * <th scope="col" id="predef_classes">Classes</th>
 641  * <th scope="col" id="predef_matches">Matches</th>
 642  * </tr>
 643  * </thead>
 644  * <tbody>
 645  * <tr><th scope="row">{@code \p{Lower}}</th>
 646  *     <td>A lowercase character:{@code \p{IsLowercase}}</td></tr>
 647  * <tr><th scope="row">{@code \p{Upper}}</th>
 648  *     <td>An uppercase character:{@code \p{IsUppercase}}</td></tr>
 649  * <tr><th scope="row">{@code \p{ASCII}}</th>
 650  *     <td>All ASCII:{@code [\x00-\x7F]}</td></tr>
 651  * <tr><th scope="row">{@code \p{Alpha}}</th>
 652  *     <td>An alphabetic character:{@code \p{IsAlphabetic}}</td></tr>
 653  * <tr><th scope="row">{@code \p{Digit}}</th>
 654  *     <td>A decimal digit character:{@code \p{IsDigit}}</td></tr>
 655  * <tr><th scope="row">{@code \p{Alnum}}</th>
 656  *     <td>An alphanumeric character:{@code [\p{IsAlphabetic}\p{IsDigit}]}</td></tr>
 657  * <tr><th scope="row">{@code \p{Punct}}</th>
 658  *     <td>A punctuation character:{@code \p{IsPunctuation}}</td></tr>
 659  * <tr><th scope="row">{@code \p{Graph}}</th>
 660  *     <td>A visible character: {@code [^\p{IsWhite_Space}\p{gc=Cc}\p{gc=Cs}\p{gc=Cn}]}</td></tr>
 661  * <tr><th scope="row">{@code \p{Print}}</th>
 662  *     <td>A printable character: {@code [\p{Graph}\p{Blank}&&[^\p{Cntrl}]]}</td></tr>
 663  * <tr><th scope="row">{@code \p{Blank}}</th>
 664  *     <td>A space or a tab: {@code [\p{IsWhite_Space}&&[^\p{gc=Zl}\p{gc=Zp}\x0a\x0b\x0c\x0d\x85]]}</td></tr>
 665  * <tr><th scope="row">{@code \p{Cntrl}}</th>
 666  *     <td>A control character: {@code \p{gc=Cc}}</td></tr>
 667  * <tr><th scope="row">{@code \p{XDigit}}</th>
 668  *     <td>A hexadecimal digit: {@code [\p{gc=Nd}\p{IsHex_Digit}]}</td></tr>
 669  * <tr><th scope="row">{@code \p{Space}}</th>
 670  *     <td>A whitespace character:{@code \p{IsWhite_Space}}</td></tr>
 671  * <tr><th scope="row">{@code \d}</th>
 672  *     <td>A digit: {@code \p{IsDigit}}</td></tr>
 673  * <tr><th scope="row">{@code \D}</th>
 674  *     <td>A non-digit: {@code [^\d]}</td></tr>
 675  * <tr><th scope="row">{@code \s}</th>
 676  *     <td>A whitespace character: {@code \p{IsWhite_Space}}</td></tr>
 677  * <tr><th scope="row">{@code \S}</th>
 678  *     <td>A non-whitespace character: {@code [^\s]}</td></tr>
 679  * <tr><th scope="row">{@code \w}</th>
 680  *     <td>A word character: {@code [\p{Alpha}\p{gc=Mn}\p{gc=Me}\p{gc=Mc}\p{Digit}\p{gc=Pc}\p{IsJoin_Control}]}</td></tr>
 681  * <tr><th scope="row">{@code \W}</th>
 682  *     <td>A non-word character: {@code [^\w]}</td></tr>
 683  * </tbody>
 684  * </table>
 685  * <p>
 686  * <a id="jcc">
 687  * Categories that behave like the java.lang.Character
 688  * boolean is<i>methodname</i> methods (except for the deprecated ones) are
 689  * available through the same <code>\p{</code><i>prop</i><code>}</code> syntax where
 690  * the specified property has the name <code>java<i>methodname</i></code></a>.
 691  *
 692  * <h2> Comparison to Perl 5 </h2>
 693  *
 694  * <p>The {@code Pattern} engine performs traditional NFA-based matching
 695  * with ordered alternation as occurs in Perl 5.
 696  *
 697  * <p> Perl constructs not supported by this class: </p>
 698  *
 699  * <ul>
 700  *    <li><p> The backreference constructs, <code>\g{</code><i>n</i><code>}</code> for
 701  *    the <i>n</i><sup>th</sup><a href="#cg">capturing group</a> and
 702  *    <code>\g{</code><i>name</i><code>}</code> for
 703  *    <a href="#groupname">named-capturing group</a>.
 704  *    </p></li>
 705  *
 706  *    <li><p> The conditional constructs
 707  *    {@code (?(}<i>condition</i>{@code )}<i>X</i>{@code )} and
 708  *    {@code (?(}<i>condition</i>{@code )}<i>X</i>{@code |}<i>Y</i>{@code )},
 709  *    </p></li>
 710  *
 711  *    <li><p> The embedded code constructs <code>(?{</code><i>code</i><code>})</code>
 712  *    and <code>(??{</code><i>code</i><code>})</code>,</p></li>
 713  *
 714  *    <li><p> The embedded comment syntax {@code (?#comment)}, and </p></li>
 715  *
 716  *    <li><p> The preprocessing operations {@code \l} <code>\u</code>,
 717  *    {@code \L}, and {@code \U}.  </p></li>
 718  *
 719  * </ul>
 720  *
 721  * <p> Constructs supported by this class but not by Perl: </p>
 722  *
 723  * <ul>
 724  *
 725  *    <li><p> Character-class union and intersection as described
 726  *    <a href="#cc">above</a>.</p></li>
 727  *
 728  * </ul>
 729  *
 730  * <p> Notable differences from Perl: </p>
 731  *
 732  * <ul>
 733  *
 734  *    <li><p> In Perl, {@code \1} through {@code \9} are always interpreted
 735  *    as back references; a backslash-escaped number greater than {@code 9} is
 736  *    treated as a back reference if at least that many subexpressions exist,
 737  *    otherwise it is interpreted, if possible, as an octal escape.  In this
 738  *    class octal escapes must always begin with a zero. In this class,
 739  *    {@code \1} through {@code \9} are always interpreted as back
 740  *    references, and a larger number is accepted as a back reference if at
 741  *    least that many subexpressions exist at that point in the regular
 742  *    expression, otherwise the parser will drop digits until the number is
 743  *    smaller or equal to the existing number of groups or it is one digit.
 744  *    </p></li>
 745  *
 746  *    <li><p> Perl uses the {@code g} flag to request a match that resumes
 747  *    where the last match left off.  This functionality is provided implicitly
 748  *    by the {@link Matcher} class: Repeated invocations of the {@link
 749  *    Matcher#find find} method will resume where the last match left off,
 750  *    unless the matcher is reset.  </p></li>
 751  *
 752  *    <li><p> In Perl, embedded flags at the top level of an expression affect
 753  *    the whole expression.  In this class, embedded flags always take effect
 754  *    at the point at which they appear, whether they are at the top level or
 755  *    within a group; in the latter case, flags are restored at the end of the
 756  *    group just as in Perl.  </p></li>
 757  *
 758  * </ul>
 759  *
 760  *
 761  * <p> For a more precise description of the behavior of regular expression
 762  * constructs, please see <a href="http://www.oreilly.com/catalog/regex3/">
 763  * <i>Mastering Regular Expressions, 3nd Edition</i>, Jeffrey E. F. Friedl,
 764  * O'Reilly and Associates, 2006.</a>
 765  * </p>
 766  *
 767  * @see java.lang.String#split(String, int)
 768  * @see java.lang.String#split(String)
 769  *
 770  * @author      Mike McCloskey
 771  * @author      Mark Reinhold
 772  * @author      JSR-51 Expert Group
 773  * @since       1.4
 774  * @spec        JSR-51
 775  */
 776 
 777 public final class Pattern
 778     implements java.io.Serializable
 779 {
 780 
 781     /**
 782      * Regular expression modifier values.  Instead of being passed as
 783      * arguments, they can also be passed as inline modifiers.
 784      * For example, the following statements have the same effect.
 785      * <pre>
 786      * Pattern p1 = Pattern.compile("abc", Pattern.CASE_INSENSITIVE|Pattern.MULTILINE);
 787      * Pattern p2 = Pattern.compile("(?im)abc", 0);
 788      * </pre>
 789      */
 790 
 791     /**
 792      * Enables Unix lines mode.
 793      *
 794      * <p> In this mode, only the {@code '\n'} line terminator is recognized
 795      * in the behavior of {@code .}, {@code ^}, and {@code $}.
 796      *
 797      * <p> Unix lines mode can also be enabled via the embedded flag
 798      * expression&nbsp;{@code (?d)}.
 799      */
 800     public static final int UNIX_LINES = 0x01;
 801 
 802     /**
 803      * Enables case-insensitive matching.
 804      *
 805      * <p> By default, case-insensitive matching assumes that only characters
 806      * in the US-ASCII charset are being matched.  Unicode-aware
 807      * case-insensitive matching can be enabled by specifying the {@link
 808      * #UNICODE_CASE} flag in conjunction with this flag.
 809      *
 810      * <p> Case-insensitive matching can also be enabled via the embedded flag
 811      * expression&nbsp;{@code (?i)}.
 812      *
 813      * <p> Specifying this flag may impose a slight performance penalty.  </p>
 814      */
 815     public static final int CASE_INSENSITIVE = 0x02;
 816 
 817     /**
 818      * Permits whitespace and comments in pattern.
 819      *
 820      * <p> In this mode, whitespace is ignored, and embedded comments starting
 821      * with {@code #} are ignored until the end of a line.
 822      *
 823      * <p> Comments mode can also be enabled via the embedded flag
 824      * expression&nbsp;{@code (?x)}.
 825      */
 826     public static final int COMMENTS = 0x04;
 827 
 828     /**
 829      * Enables multiline mode.
 830      *
 831      * <p> In multiline mode the expressions {@code ^} and {@code $} match
 832      * just after or just before, respectively, a line terminator or the end of
 833      * the input sequence.  By default these expressions only match at the
 834      * beginning and the end of the entire input sequence.
 835      *
 836      * <p> Multiline mode can also be enabled via the embedded flag
 837      * expression&nbsp;{@code (?m)}.  </p>
 838      */
 839     public static final int MULTILINE = 0x08;
 840 
 841     /**
 842      * Enables literal parsing of the pattern.
 843      *
 844      * <p> When this flag is specified then the input string that specifies
 845      * the pattern is treated as a sequence of literal characters.
 846      * Metacharacters or escape sequences in the input sequence will be
 847      * given no special meaning.
 848      *
 849      * <p>The flags CASE_INSENSITIVE and UNICODE_CASE retain their impact on
 850      * matching when used in conjunction with this flag. The other flags
 851      * become superfluous.
 852      *
 853      * <p> There is no embedded flag character for enabling literal parsing.
 854      * @since 1.5
 855      */
 856     public static final int LITERAL = 0x10;
 857 
 858     /**
 859      * Enables dotall mode.
 860      *
 861      * <p> In dotall mode, the expression {@code .} matches any character,
 862      * including a line terminator.  By default this expression does not match
 863      * line terminators.
 864      *
 865      * <p> Dotall mode can also be enabled via the embedded flag
 866      * expression&nbsp;{@code (?s)}.  (The {@code s} is a mnemonic for
 867      * "single-line" mode, which is what this is called in Perl.)  </p>
 868      */
 869     public static final int DOTALL = 0x20;
 870 
 871     /**
 872      * Enables Unicode-aware case folding.
 873      *
 874      * <p> When this flag is specified then case-insensitive matching, when
 875      * enabled by the {@link #CASE_INSENSITIVE} flag, is done in a manner
 876      * consistent with the Unicode Standard.  By default, case-insensitive
 877      * matching assumes that only characters in the US-ASCII charset are being
 878      * matched.
 879      *
 880      * <p> Unicode-aware case folding can also be enabled via the embedded flag
 881      * expression&nbsp;{@code (?u)}.
 882      *
 883      * <p> Specifying this flag may impose a performance penalty.  </p>
 884      */
 885     public static final int UNICODE_CASE = 0x40;
 886 
 887     /**
 888      * Enables canonical equivalence.
 889      *
 890      * <p> When this flag is specified then two characters will be considered
 891      * to match if, and only if, their full canonical decompositions match.
 892      * The expression <code>"a\u030A"</code>, for example, will match the
 893      * string <code>"\u00E5"</code> when this flag is specified.  By default,
 894      * matching does not take canonical equivalence into account.
 895      *
 896      * <p> There is no embedded flag character for enabling canonical
 897      * equivalence.
 898      *
 899      * <p> Specifying this flag may impose a performance penalty.  </p>
 900      */
 901     public static final int CANON_EQ = 0x80;
 902 
 903     /**
 904      * Enables the Unicode version of <i>Predefined character classes</i> and
 905      * <i>POSIX character classes</i>.
 906      *
 907      * <p> When this flag is specified then the (US-ASCII only)
 908      * <i>Predefined character classes</i> and <i>POSIX character classes</i>
 909      * are in conformance with
 910      * <a href="http://www.unicode.org/reports/tr18/"><i>Unicode Technical
 911      * Standard #18: Unicode Regular Expression</i></a>
 912      * <i>Annex C: Compatibility Properties</i>.
 913      * <p>
 914      * The UNICODE_CHARACTER_CLASS mode can also be enabled via the embedded
 915      * flag expression&nbsp;{@code (?U)}.
 916      * <p>
 917      * The flag implies UNICODE_CASE, that is, it enables Unicode-aware case
 918      * folding.
 919      * <p>
 920      * Specifying this flag may impose a performance penalty.  </p>
 921      * @since 1.7
 922      */
 923     public static final int UNICODE_CHARACTER_CLASS = 0x100;
 924 
 925     /**
 926      * Contains all possible flags for compile(regex, flags).
 927      */
 928     private static final int ALL_FLAGS = CASE_INSENSITIVE | MULTILINE |
 929             DOTALL | UNICODE_CASE | CANON_EQ | UNIX_LINES | LITERAL |
 930             UNICODE_CHARACTER_CLASS | COMMENTS;
 931 
 932     /* Pattern has only two serialized components: The pattern string
 933      * and the flags, which are all that is needed to recompile the pattern
 934      * when it is deserialized.
 935      */
 936 
 937     /** use serialVersionUID from Merlin b59 for interoperability */
 938     private static final long serialVersionUID = 5073258162644648461L;
 939 
 940     /**
 941      * The original regular-expression pattern string.
 942      *
 943      * @serial
 944      */
 945     private String pattern;
 946 
 947     /**
 948      * The original pattern flags.
 949      *
 950      * @serial
 951      */
 952     private int flags;
 953 
 954     /**
 955      * The temporary pattern flags used during compiling. The flags might be turn
 956      * on and off by embedded flag.
 957      */
 958     private transient int flags0;
 959 
 960     /**
 961      * Boolean indicating this Pattern is compiled; this is necessary in order
 962      * to lazily compile deserialized Patterns.
 963      */
 964     private transient volatile boolean compiled;
 965 
 966     /**
 967      * The normalized pattern string.
 968      */
 969     private transient String normalizedPattern;
 970 
 971     /**
 972      * The starting point of state machine for the find operation.  This allows
 973      * a match to start anywhere in the input.
 974      */
 975     transient Node root;
 976 
 977     /**
 978      * The root of object tree for a match operation.  The pattern is matched
 979      * at the beginning.  This may include a find that uses BnM or a First
 980      * node.
 981      */
 982     transient Node matchRoot;
 983 
 984     /**
 985      * Temporary storage used by parsing pattern slice.
 986      */
 987     transient int[] buffer;
 988 
 989     /**
 990      * A temporary storage used for predicate for double return.
 991      */
 992     transient CharPredicate predicate;
 993 
 994     /**
 995      * Map the "name" of the "named capturing group" to its group id
 996      * node.
 997      */
 998     transient volatile Map<String, Integer> namedGroups;
 999 
1000     /**
1001      * Temporary storage used while parsing group references.
1002      */
1003     transient GroupHead[] groupNodes;
1004 
1005     /**
1006      * Temporary storage used to store the top level closure nodes.
1007      */
1008     transient List<Node> topClosureNodes;
1009 
1010     /**
1011      * The number of top greedy closure nodes in this Pattern. Used by
1012      * matchers to allocate storage needed for a IntHashSet to keep the
1013      * beginning pos {@code i} of all failed match.
1014      */
1015     transient int localTCNCount;
1016 
1017     /*
1018      * Turn off the stop-exponential-backtracking optimization if there
1019      * is a group ref in the pattern.
1020      */
1021     transient boolean hasGroupRef;
1022 
1023     /**
1024      * Temporary null terminated code point array used by pattern compiling.
1025      */
1026     private transient int[] temp;
1027 
1028     /**
1029      * The number of capturing groups in this Pattern. Used by matchers to
1030      * allocate storage needed to perform a match.
1031      */
1032     transient int capturingGroupCount;
1033 
1034     /**
1035      * The local variable count used by parsing tree. Used by matchers to
1036      * allocate storage needed to perform a match.
1037      */
1038     transient int localCount;
1039 
1040     /**
1041      * Index into the pattern string that keeps track of how much has been
1042      * parsed.
1043      */
1044     private transient int cursor;
1045 
1046     /**
1047      * Holds the length of the pattern string.
1048      */
1049     private transient int patternLength;
1050 
1051     /**
1052      * If the Start node might possibly match supplementary characters.
1053      * It is set to true during compiling if
1054      * (1) There is supplementary char in pattern, or
1055      * (2) There is complement node of a "family" CharProperty
1056      */
1057     private transient boolean hasSupplementary;
1058 
1059     /**
1060      * Compiles the given regular expression into a pattern.
1061      *
1062      * @param  regex
1063      *         The expression to be compiled
1064      * @return the given regular expression compiled into a pattern
1065      * @throws  PatternSyntaxException
1066      *          If the expression's syntax is invalid
1067      */
1068     public static Pattern compile(String regex) {
1069         return new Pattern(regex, 0);
1070     }
1071 
1072     /**
1073      * Compiles the given regular expression into a pattern with the given
1074      * flags.
1075      *
1076      * @param  regex
1077      *         The expression to be compiled
1078      *
1079      * @param  flags
1080      *         Match flags, a bit mask that may include
1081      *         {@link #CASE_INSENSITIVE}, {@link #MULTILINE}, {@link #DOTALL},
1082      *         {@link #UNICODE_CASE}, {@link #CANON_EQ}, {@link #UNIX_LINES},
1083      *         {@link #LITERAL}, {@link #UNICODE_CHARACTER_CLASS}
1084      *         and {@link #COMMENTS}
1085      *
1086      * @return the given regular expression compiled into a pattern with the given flags
1087      * @throws  IllegalArgumentException
1088      *          If bit values other than those corresponding to the defined
1089      *          match flags are set in {@code flags}
1090      *
1091      * @throws  PatternSyntaxException
1092      *          If the expression's syntax is invalid
1093      */
1094     public static Pattern compile(String regex, int flags) {
1095         return new Pattern(regex, flags);
1096     }
1097 
1098     /**
1099      * Returns the regular expression from which this pattern was compiled.
1100      *
1101      * @return  The source of this pattern
1102      */
1103     public String pattern() {
1104         return pattern;
1105     }
1106 
1107     /**
1108      * <p>Returns the string representation of this pattern. This
1109      * is the regular expression from which this pattern was
1110      * compiled.</p>
1111      *
1112      * @return  The string representation of this pattern
1113      * @since 1.5
1114      */
1115     public String toString() {
1116         return pattern;
1117     }
1118 
1119     /**
1120      * Creates a matcher that will match the given input against this pattern.
1121      *
1122      * @param  input
1123      *         The character sequence to be matched
1124      *
1125      * @return  A new matcher for this pattern
1126      */
1127     public Matcher matcher(CharSequence input) {
1128         if (!compiled) {
1129             synchronized(this) {
1130                 if (!compiled)
1131                     compile();
1132             }
1133         }
1134         Matcher m = new Matcher(this, input);
1135         return m;
1136     }
1137 
1138     /**
1139      * Returns this pattern's match flags.
1140      *
1141      * @return  The match flags specified when this pattern was compiled
1142      */
1143     public int flags() {
1144         return flags0;
1145     }
1146 
1147     /**
1148      * Compiles the given regular expression and attempts to match the given
1149      * input against it.
1150      *
1151      * <p> An invocation of this convenience method of the form
1152      *
1153      * <blockquote><pre>
1154      * Pattern.matches(regex, input);</pre></blockquote>
1155      *
1156      * behaves in exactly the same way as the expression
1157      *
1158      * <blockquote><pre>
1159      * Pattern.compile(regex).matcher(input).matches()</pre></blockquote>
1160      *
1161      * <p> If a pattern is to be used multiple times, compiling it once and reusing
1162      * it will be more efficient than invoking this method each time.  </p>
1163      *
1164      * @param  regex
1165      *         The expression to be compiled
1166      *
1167      * @param  input
1168      *         The character sequence to be matched
1169      * @return whether or not the regular expression matches on the input
1170      * @throws  PatternSyntaxException
1171      *          If the expression's syntax is invalid
1172      */
1173     public static boolean matches(String regex, CharSequence input) {
1174         Pattern p = Pattern.compile(regex);
1175         Matcher m = p.matcher(input);
1176         return m.matches();
1177     }
1178 
1179     /**
1180      * Splits the given input sequence around matches of this pattern.
1181      *
1182      * <p> The array returned by this method contains each substring of the
1183      * input sequence that is terminated by another subsequence that matches
1184      * this pattern or is terminated by the end of the input sequence.  The
1185      * substrings in the array are in the order in which they occur in the
1186      * input. If this pattern does not match any subsequence of the input then
1187      * the resulting array has just one element, namely the input sequence in
1188      * string form.
1189      *
1190      * <p> When there is a positive-width match at the beginning of the input
1191      * sequence then an empty leading substring is included at the beginning
1192      * of the resulting array. A zero-width match at the beginning however
1193      * never produces such empty leading substring.
1194      *
1195      * <p> The {@code limit} parameter controls the number of times the
1196      * pattern is applied and therefore affects the length of the resulting
1197      * array.
1198      * <ul>
1199      *    <li><p>
1200      *    If the <i>limit</i> is positive then the pattern will be applied
1201      *    at most <i>limit</i>&nbsp;-&nbsp;1 times, the array's length will be
1202      *    no greater than <i>limit</i>, and the array's last entry will contain
1203      *    all input beyond the last matched delimiter.</p></li>
1204      *
1205      *    <li><p>
1206      *    If the <i>limit</i> is zero then the pattern will be applied as
1207      *    many times as possible, the array can have any length, and trailing
1208      *    empty strings will be discarded.</p></li>
1209      *
1210      *    <li><p>
1211      *    If the <i>limit</i> is negative then the pattern will be applied
1212      *    as many times as possible and the array can have any length.</p></li>
1213      * </ul>
1214      *
1215      * <p> The input {@code "boo:and:foo"}, for example, yields the following
1216      * results with these parameters:
1217      *
1218      * <table class="plain" style="margin-left:2em;">
1219      * <caption style="display:none">Split example showing regex, limit, and result</caption>
1220      * <thead>
1221      * <tr>
1222      *     <th scope="col">Regex</th>
1223      *     <th scope="col">Limit</th>
1224      *     <th scope="col">Result</th>
1225      * </tr>
1226      * </thead>
1227      * <tbody>
1228      * <tr><th scope="row" rowspan="3" style="font-weight:normal">:</th>
1229      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">2</th>
1230      *     <td>{@code { "boo", "and:foo" }}</td></tr>
1231      * <tr><!-- : -->
1232      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
1233      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
1234      * <tr><!-- : -->
1235      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
1236      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
1237      * <tr><th scope="row" rowspan="3" style="font-weight:normal">o</th>
1238      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">5</th>
1239      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1240      * <tr><!-- o -->
1241      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">-2</th>
1242      *     <td>{@code { "b", "", ":and:f", "", "" }}</td></tr>
1243      * <tr><!-- o -->
1244      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">0</th>
1245      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
1246      * </tbody>
1247      * </table>
1248      *
1249      * @param  input
1250      *         The character sequence to be split
1251      *
1252      * @param  limit
1253      *         The result threshold, as described above
1254      *
1255      * @return  The array of strings computed by splitting the input
1256      *          around matches of this pattern
1257      */
1258     public String[] split(CharSequence input, int limit) {
1259         int index = 0;
1260         boolean matchLimited = limit > 0;
1261         ArrayList<String> matchList = new ArrayList<>();
1262         Matcher m = matcher(input);
1263 
1264         // Add segments before each match found
1265         while(m.find()) {
1266             if (!matchLimited || matchList.size() < limit - 1) {
1267                 if (index == 0 && index == m.start() && m.start() == m.end()) {
1268                     // no empty leading substring included for zero-width match
1269                     // at the beginning of the input char sequence.
1270                     continue;
1271                 }
1272                 String match = input.subSequence(index, m.start()).toString();
1273                 matchList.add(match);
1274                 index = m.end();
1275             } else if (matchList.size() == limit - 1) { // last one
1276                 String match = input.subSequence(index,
1277                                                  input.length()).toString();
1278                 matchList.add(match);
1279                 index = m.end();
1280             }
1281         }
1282 
1283         // If no match was found, return this
1284         if (index == 0)
1285             return new String[] {input.toString()};
1286 
1287         // Add remaining segment
1288         if (!matchLimited || matchList.size() < limit)
1289             matchList.add(input.subSequence(index, input.length()).toString());
1290 
1291         // Construct result
1292         int resultSize = matchList.size();
1293         if (limit == 0)
1294             while (resultSize > 0 && matchList.get(resultSize-1).isEmpty())
1295                 resultSize--;
1296         String[] result = new String[resultSize];
1297         return matchList.subList(0, resultSize).toArray(result);
1298     }
1299 
1300     /**
1301      * Splits the given input sequence around matches of this pattern.
1302      *
1303      * <p> This method works as if by invoking the two-argument {@link
1304      * #split(java.lang.CharSequence, int) split} method with the given input
1305      * sequence and a limit argument of zero.  Trailing empty strings are
1306      * therefore not included in the resulting array. </p>
1307      *
1308      * <p> The input {@code "boo:and:foo"}, for example, yields the following
1309      * results with these expressions:
1310      *
1311      * <table class="plain" style="margin-left:2em">
1312      * <caption style="display:none">Split examples showing regex and result</caption>
1313      * <thead>
1314      * <tr>
1315      *  <th scope="col">Regex</th>
1316      *  <th scope="col">Result</th>
1317      * </tr>
1318      * </thead>
1319      * <tbody>
1320      * <tr><th scope="row" style="text-weight:normal">:</th>
1321      *     <td>{@code { "boo", "and", "foo" }}</td></tr>
1322      * <tr><th scope="row" style="text-weight:normal">o</th>
1323      *     <td>{@code { "b", "", ":and:f" }}</td></tr>
1324      * </tbody>
1325      * </table>
1326      *
1327      *
1328      * @param  input
1329      *         The character sequence to be split
1330      *
1331      * @return  The array of strings computed by splitting the input
1332      *          around matches of this pattern
1333      */
1334     public String[] split(CharSequence input) {
1335         return split(input, 0);
1336     }
1337 
1338     /**
1339      * Returns a literal pattern {@code String} for the specified
1340      * {@code String}.
1341      *
1342      * <p>This method produces a {@code String} that can be used to
1343      * create a {@code Pattern} that would match the string
1344      * {@code s} as if it were a literal pattern.</p> Metacharacters
1345      * or escape sequences in the input sequence will be given no special
1346      * meaning.
1347      *
1348      * @param  s The string to be literalized
1349      * @return  A literal string replacement
1350      * @since 1.5
1351      */
1352     public static String quote(String s) {
1353         int slashEIndex = s.indexOf("\\E");
1354         if (slashEIndex == -1)
1355             return "\\Q" + s + "\\E";
1356 
1357         int lenHint = s.length();
1358         lenHint = (lenHint < Integer.MAX_VALUE - 8 - lenHint) ?
1359                 (lenHint << 1) : (Integer.MAX_VALUE - 8);
1360 
1361         StringBuilder sb = new StringBuilder(lenHint);
1362         sb.append("\\Q");
1363         int current = 0;
1364         do {
1365             sb.append(s, current, slashEIndex)
1366                     .append("\\E\\\\E\\Q");
1367             current = slashEIndex + 2;
1368         } while ((slashEIndex = s.indexOf("\\E", current)) != -1);
1369 
1370         return sb.append(s, current, s.length())
1371                 .append("\\E")
1372                 .toString();
1373     }
1374 
1375     /**
1376      * Recompile the Pattern instance from a stream.  The original pattern
1377      * string is read in and the object tree is recompiled from it.
1378      */
1379     private void readObject(java.io.ObjectInputStream s)
1380         throws java.io.IOException, ClassNotFoundException {
1381 
1382         // Read in all fields
1383         s.defaultReadObject();
1384 
1385         // reset the flags
1386         flags0 = flags;
1387 
1388         // Initialize counts
1389         capturingGroupCount = 1;
1390         localCount = 0;
1391         localTCNCount = 0;
1392 
1393         // if length > 0, the Pattern is lazily compiled
1394         if (pattern.isEmpty()) {
1395             root = new Start(lastAccept);
1396             matchRoot = lastAccept;
1397             compiled = true;
1398         }
1399     }
1400 
1401     /**
1402      * This private constructor is used to create all Patterns. The pattern
1403      * string and match flags are all that is needed to completely describe
1404      * a Pattern. An empty pattern string results in an object tree with
1405      * only a Start node and a LastNode node.
1406      */
1407     private Pattern(String p, int f) {
1408         if ((f & ~ALL_FLAGS) != 0) {
1409             throw new IllegalArgumentException("Unknown flag 0x"
1410                                                + Integer.toHexString(f));
1411         }
1412         pattern = p;
1413         flags = f;
1414 
1415         // to use UNICODE_CASE if UNICODE_CHARACTER_CLASS present
1416         if ((flags & UNICODE_CHARACTER_CLASS) != 0)
1417             flags |= UNICODE_CASE;
1418 
1419         // 'flags' for compiling
1420         flags0 = flags;
1421 
1422         // Reset group index count
1423         capturingGroupCount = 1;
1424         localCount = 0;
1425         localTCNCount = 0;
1426 
1427         if (!pattern.isEmpty()) {
1428             compile();
1429         } else {
1430             root = new Start(lastAccept);
1431             matchRoot = lastAccept;
1432         }
1433     }
1434 
1435     /**
1436      * The pattern is converted to normalized form ({@link
1437      * java.text.Normalizer.Form#NFC NFC}, canonical decomposition,
1438      * followed by canonical composition for the character class
1439      * part, and {@link java.text.Normalizer.Form#NFD NFD},
1440      * canonical decomposition for the rest), and then a pure
1441      * group is constructed to match canonical equivalences of the
1442      * characters.
1443      */
1444     private static String normalize(String pattern) {
1445         int plen = pattern.length();
1446         StringBuilder pbuf = new StringBuilder(plen);
1447         char last = 0;
1448         int lastStart = 0;
1449         char cc = 0;
1450         for (int i = 0; i < plen;) {
1451             char c = pattern.charAt(i);
1452             if (cc == 0 &&    // top level
1453                 c == '\\' && i + 1 < plen && pattern.charAt(i + 1) == '\\') {
1454                 i += 2; last = 0;
1455                 continue;
1456             }
1457             if (c == '[' && last != '\\') {
1458                 if (cc == 0) {
1459                     if (lastStart < i)
1460                         normalizeSlice(pattern, lastStart, i, pbuf);
1461                     lastStart = i;
1462                 }
1463                 cc++;
1464             } else if (c == ']' && last != '\\') {
1465                 cc--;
1466                 if (cc == 0) {
1467                     normalizeClazz(pattern, lastStart, i + 1, pbuf);
1468                     lastStart = i + 1;
1469                 }
1470             }
1471             last = c;
1472             i++;
1473         }
1474         assert (cc == 0);
1475         if (lastStart < plen)
1476             normalizeSlice(pattern, lastStart, plen, pbuf);
1477         return pbuf.toString();
1478     }
1479 
1480     private static void normalizeSlice(String src, int off, int limit,
1481                                        StringBuilder dst)
1482     {
1483         int len = src.length();
1484         int off0 = off;
1485         while (off < limit && ASCII.isAscii(src.charAt(off))) {
1486             off++;
1487         }
1488         if (off == limit) {
1489             dst.append(src, off0, limit);
1490             return;
1491         }
1492         off--;
1493         if (off < off0)
1494             off = off0;
1495         else
1496             dst.append(src, off0, off);
1497         while (off < limit) {
1498             int ch0 = src.codePointAt(off);
1499             if (".$|()[]{}^?*+\\".indexOf(ch0) != -1) {
1500                 dst.append((char)ch0);
1501                 off++;
1502                 continue;
1503             }
1504             int j = Grapheme.nextBoundary(src, off, limit);
1505             int ch1;
1506             String seq = src.substring(off, j);
1507             String nfd = Normalizer.normalize(seq, Normalizer.Form.NFD);
1508             off = j;
1509             if (nfd.length() > 1) {
1510                 ch0 = nfd.codePointAt(0);
1511                 ch1 = nfd.codePointAt(Character.charCount(ch0));
1512                 if (Character.getType(ch1) == Character.NON_SPACING_MARK) {
1513                     Set<String> altns = new LinkedHashSet<>();
1514                     altns.add(seq);
1515                     produceEquivalentAlternation(nfd, altns);
1516                     dst.append("(?:");
1517                     altns.forEach( s -> dst.append(s).append('|'));
1518                     dst.delete(dst.length() - 1, dst.length());
1519                     dst.append(")");
1520                     continue;
1521                 }
1522             }
1523             String nfc = Normalizer.normalize(seq, Normalizer.Form.NFC);
1524             if (!seq.equals(nfc) && !nfd.equals(nfc))
1525                 dst.append("(?:" + seq + "|" + nfd  + "|" + nfc + ")");
1526             else if (!seq.equals(nfd))
1527                 dst.append("(?:" + seq + "|" + nfd + ")");
1528             else
1529                 dst.append(seq);
1530         }
1531     }
1532 
1533     private static void normalizeClazz(String src, int off, int limit,
1534                                        StringBuilder dst)
1535     {
1536         dst.append(Normalizer.normalize(src.substring(off, limit), Form.NFC));
1537     }
1538 
1539     /**
1540      * Given a specific sequence composed of a regular character and
1541      * combining marks that follow it, produce the alternation that will
1542      * match all canonical equivalences of that sequence.
1543      */
1544     private static void produceEquivalentAlternation(String src,
1545                                                      Set<String> dst)
1546     {
1547         int len = countChars(src, 0, 1);
1548         if (src.length() == len) {
1549             dst.add(src);  // source has one character.
1550             return;
1551         }
1552         String base = src.substring(0,len);
1553         String combiningMarks = src.substring(len);
1554         String[] perms = producePermutations(combiningMarks);
1555         // Add combined permutations
1556         for(int x = 0; x < perms.length; x++) {
1557             String next = base + perms[x];
1558             dst.add(next);
1559             next = composeOneStep(next);
1560             if (next != null) {
1561                 produceEquivalentAlternation(next, dst);
1562             }
1563         }
1564     }
1565 
1566     /**
1567      * Returns an array of strings that have all the possible
1568      * permutations of the characters in the input string.
1569      * This is used to get a list of all possible orderings
1570      * of a set of combining marks. Note that some of the permutations
1571      * are invalid because of combining class collisions, and these
1572      * possibilities must be removed because they are not canonically
1573      * equivalent.
1574      */
1575     private static String[] producePermutations(String input) {
1576         if (input.length() == countChars(input, 0, 1))
1577             return new String[] {input};
1578 
1579         if (input.length() == countChars(input, 0, 2)) {
1580             int c0 = Character.codePointAt(input, 0);
1581             int c1 = Character.codePointAt(input, Character.charCount(c0));
1582             if (getClass(c1) == getClass(c0)) {
1583                 return new String[] {input};
1584             }
1585             String[] result = new String[2];
1586             result[0] = input;
1587             StringBuilder sb = new StringBuilder(2);
1588             sb.appendCodePoint(c1);
1589             sb.appendCodePoint(c0);
1590             result[1] = sb.toString();
1591             return result;
1592         }
1593 
1594         int length = 1;
1595         int nCodePoints = countCodePoints(input);
1596         for(int x=1; x<nCodePoints; x++)
1597             length = length * (x+1);
1598 
1599         String[] temp = new String[length];
1600 
1601         int combClass[] = new int[nCodePoints];
1602         for(int x=0, i=0; x<nCodePoints; x++) {
1603             int c = Character.codePointAt(input, i);
1604             combClass[x] = getClass(c);
1605             i +=  Character.charCount(c);
1606         }
1607 
1608         // For each char, take it out and add the permutations
1609         // of the remaining chars
1610         int index = 0;
1611         int len;
1612         // offset maintains the index in code units.
1613 loop:   for(int x=0, offset=0; x<nCodePoints; x++, offset+=len) {
1614             len = countChars(input, offset, 1);
1615             for(int y=x-1; y>=0; y--) {
1616                 if (combClass[y] == combClass[x]) {
1617                     continue loop;
1618                 }
1619             }
1620             StringBuilder sb = new StringBuilder(input);
1621             String otherChars = sb.delete(offset, offset+len).toString();
1622             String[] subResult = producePermutations(otherChars);
1623 
1624             String prefix = input.substring(offset, offset+len);
1625             for (String sre : subResult)
1626                 temp[index++] = prefix + sre;
1627         }
1628         String[] result = new String[index];
1629         System.arraycopy(temp, 0, result, 0, index);
1630         return result;
1631     }
1632 
1633     private static int getClass(int c) {
1634         return sun.text.Normalizer.getCombiningClass(c);
1635     }
1636 
1637     /**
1638      * Attempts to compose input by combining the first character
1639      * with the first combining mark following it. Returns a String
1640      * that is the composition of the leading character with its first
1641      * combining mark followed by the remaining combining marks. Returns
1642      * null if the first two characters cannot be further composed.
1643      */
1644     private static String composeOneStep(String input) {
1645         int len = countChars(input, 0, 2);
1646         String firstTwoCharacters = input.substring(0, len);
1647         String result = Normalizer.normalize(firstTwoCharacters, Normalizer.Form.NFC);
1648         if (result.equals(firstTwoCharacters))
1649             return null;
1650         else {
1651             String remainder = input.substring(len);
1652             return result + remainder;
1653         }
1654     }
1655 
1656     /**
1657      * Preprocess any \Q...\E sequences in `temp', meta-quoting them.
1658      * See the description of `quotemeta' in perlfunc(1).
1659      */
1660     private void RemoveQEQuoting() {
1661         final int pLen = patternLength;
1662         int i = 0;
1663         while (i < pLen-1) {
1664             if (temp[i] != '\\')
1665                 i += 1;
1666             else if (temp[i + 1] != 'Q')
1667                 i += 2;
1668             else
1669                 break;
1670         }
1671         if (i >= pLen - 1)    // No \Q sequence found
1672             return;
1673         int j = i;
1674         i += 2;
1675         int newTempLen;
1676         try {
1677             newTempLen = Math.addExact(j + 2, Math.multiplyExact(3, pLen - i));
1678         } catch (ArithmeticException ae) {
1679             throw new OutOfMemoryError();
1680         }
1681         int[] newtemp = new int[newTempLen];
1682         System.arraycopy(temp, 0, newtemp, 0, j);
1683 
1684         boolean inQuote = true;
1685         boolean beginQuote = true;
1686         while (i < pLen) {
1687             int c = temp[i++];
1688             if (!ASCII.isAscii(c) || ASCII.isAlpha(c)) {
1689                 newtemp[j++] = c;
1690             } else if (ASCII.isDigit(c)) {
1691                 if (beginQuote) {
1692                     /*
1693                      * A unicode escape \[0xu] could be before this quote,
1694                      * and we don't want this numeric char to processed as
1695                      * part of the escape.
1696                      */
1697                     newtemp[j++] = '\\';
1698                     newtemp[j++] = 'x';
1699                     newtemp[j++] = '3';
1700                 }
1701                 newtemp[j++] = c;
1702             } else if (c != '\\') {
1703                 if (inQuote) newtemp[j++] = '\\';
1704                 newtemp[j++] = c;
1705             } else if (inQuote) {
1706                 if (temp[i] == 'E') {
1707                     i++;
1708                     inQuote = false;
1709                 } else {
1710                     newtemp[j++] = '\\';
1711                     newtemp[j++] = '\\';
1712                 }
1713             } else {
1714                 if (temp[i] == 'Q') {
1715                     i++;
1716                     inQuote = true;
1717                     beginQuote = true;
1718                     continue;
1719                 } else {
1720                     newtemp[j++] = c;
1721                     if (i != pLen)
1722                         newtemp[j++] = temp[i++];
1723                 }
1724             }
1725 
1726             beginQuote = false;
1727         }
1728 
1729         patternLength = j;
1730         temp = Arrays.copyOf(newtemp, j + 2); // double zero termination
1731     }
1732 
1733     /**
1734      * Copies regular expression to an int array and invokes the parsing
1735      * of the expression which will create the object tree.
1736      */
1737     private void compile() {
1738         // Handle canonical equivalences
1739         if (has(CANON_EQ) && !has(LITERAL)) {
1740             normalizedPattern = normalize(pattern);
1741         } else {
1742             normalizedPattern = pattern;
1743         }
1744         patternLength = normalizedPattern.length();
1745 
1746         // Copy pattern to int array for convenience
1747         // Use double zero to terminate pattern
1748         temp = new int[patternLength + 2];
1749 
1750         hasSupplementary = false;
1751         int c, count = 0;
1752         // Convert all chars into code points
1753         for (int x = 0; x < patternLength; x += Character.charCount(c)) {
1754             c = normalizedPattern.codePointAt(x);
1755             if (isSupplementary(c)) {
1756                 hasSupplementary = true;
1757             }
1758             temp[count++] = c;
1759         }
1760 
1761         patternLength = count;   // patternLength now in code points
1762 
1763         if (! has(LITERAL))
1764             RemoveQEQuoting();
1765 
1766         // Allocate all temporary objects here.
1767         buffer = new int[32];
1768         groupNodes = new GroupHead[10];
1769         namedGroups = null;
1770         topClosureNodes = new ArrayList<>(10);
1771 
1772         if (has(LITERAL)) {
1773             // Literal pattern handling
1774             matchRoot = newSlice(temp, patternLength, hasSupplementary);
1775             matchRoot.next = lastAccept;
1776         } else {
1777             // Start recursive descent parsing
1778             matchRoot = expr(lastAccept);
1779             // Check extra pattern characters
1780             if (patternLength != cursor) {
1781                 if (peek() == ')') {
1782                     throw error("Unmatched closing ')'");
1783                 } else {
1784                     throw error("Unexpected internal error");
1785                 }
1786             }
1787         }
1788 
1789         // Peephole optimization
1790         if (matchRoot instanceof Slice) {
1791             root = BnM.optimize(matchRoot);
1792             if (root == matchRoot) {
1793                 root = hasSupplementary ? new StartS(matchRoot) : new Start(matchRoot);
1794             }
1795         } else if (matchRoot instanceof Begin || matchRoot instanceof First) {
1796             root = matchRoot;
1797         } else {
1798             root = hasSupplementary ? new StartS(matchRoot) : new Start(matchRoot);
1799         }
1800 
1801         // Optimize the greedy Loop to prevent exponential backtracking, IF there
1802         // is no group ref in this pattern. With a non-negative localTCNCount value,
1803         // the greedy type Loop, Curly will skip the backtracking for any starting
1804         // position "i" that failed in the past.
1805         if (!hasGroupRef) {
1806             for (Node node : topClosureNodes) {
1807                 if (node instanceof Loop) {
1808                     // non-deterministic-greedy-group
1809                     ((Loop)node).posIndex = localTCNCount++;
1810                 }
1811             }
1812         }
1813 
1814         // Release temporary storage
1815         temp = null;
1816         buffer = null;
1817         groupNodes = null;
1818         patternLength = 0;
1819         compiled = true;
1820         topClosureNodes = null;
1821     }
1822 
1823     Map<String, Integer> namedGroups() {
1824         Map<String, Integer> groups = namedGroups;
1825         if (groups == null) {
1826             namedGroups = groups = new HashMap<>(2);
1827         }
1828         return groups;
1829     }
1830 
1831     /**
1832      * Used to accumulate information about a subtree of the object graph
1833      * so that optimizations can be applied to the subtree.
1834      */
1835     static final class TreeInfo {
1836         int minLength;
1837         int maxLength;
1838         boolean maxValid;
1839         boolean deterministic;
1840 
1841         TreeInfo() {
1842             reset();
1843         }
1844         void reset() {
1845             minLength = 0;
1846             maxLength = 0;
1847             maxValid = true;
1848             deterministic = true;
1849         }
1850     }
1851 
1852     /*
1853      * The following private methods are mainly used to improve the
1854      * readability of the code. In order to let the Java compiler easily
1855      * inline them, we should not put many assertions or error checks in them.
1856      */
1857 
1858     /**
1859      * Indicates whether a particular flag is set or not.
1860      */
1861     private boolean has(int f) {
1862         return (flags0 & f) != 0;
1863     }
1864 
1865     /**
1866      * Match next character, signal error if failed.
1867      */
1868     private void accept(int ch, String s) {
1869         int testChar = temp[cursor++];
1870         if (has(COMMENTS))
1871             testChar = parsePastWhitespace(testChar);
1872         if (ch != testChar) {
1873             throw error(s);
1874         }
1875     }
1876 
1877     /**
1878      * Mark the end of pattern with a specific character.
1879      */
1880     private void mark(int c) {
1881         temp[patternLength] = c;
1882     }
1883 
1884     /**
1885      * Peek the next character, and do not advance the cursor.
1886      */
1887     private int peek() {
1888         int ch = temp[cursor];
1889         if (has(COMMENTS))
1890             ch = peekPastWhitespace(ch);
1891         return ch;
1892     }
1893 
1894     /**
1895      * Read the next character, and advance the cursor by one.
1896      */
1897     private int read() {
1898         int ch = temp[cursor++];
1899         if (has(COMMENTS))
1900             ch = parsePastWhitespace(ch);
1901         return ch;
1902     }
1903 
1904     /**
1905      * Read the next character, and advance the cursor by one,
1906      * ignoring the COMMENTS setting
1907      */
1908     private int readEscaped() {
1909         int ch = temp[cursor++];
1910         return ch;
1911     }
1912 
1913     /**
1914      * Advance the cursor by one, and peek the next character.
1915      */
1916     private int next() {
1917         int ch = temp[++cursor];
1918         if (has(COMMENTS))
1919             ch = peekPastWhitespace(ch);
1920         return ch;
1921     }
1922 
1923     /**
1924      * Advance the cursor by one, and peek the next character,
1925      * ignoring the COMMENTS setting
1926      */
1927     private int nextEscaped() {
1928         int ch = temp[++cursor];
1929         return ch;
1930     }
1931 
1932     /**
1933      * If in xmode peek past whitespace and comments.
1934      */
1935     private int peekPastWhitespace(int ch) {
1936         while (ASCII.isSpace(ch) || ch == '#') {
1937             while (ASCII.isSpace(ch))
1938                 ch = temp[++cursor];
1939             if (ch == '#') {
1940                 ch = peekPastLine();
1941             }
1942         }
1943         return ch;
1944     }
1945 
1946     /**
1947      * If in xmode parse past whitespace and comments.
1948      */
1949     private int parsePastWhitespace(int ch) {
1950         while (ASCII.isSpace(ch) || ch == '#') {
1951             while (ASCII.isSpace(ch))
1952                 ch = temp[cursor++];
1953             if (ch == '#')
1954                 ch = parsePastLine();
1955         }
1956         return ch;
1957     }
1958 
1959     /**
1960      * xmode parse past comment to end of line.
1961      */
1962     private int parsePastLine() {
1963         int ch = temp[cursor++];
1964         while (ch != 0 && !isLineSeparator(ch))
1965             ch = temp[cursor++];
1966         return ch;
1967     }
1968 
1969     /**
1970      * xmode peek past comment to end of line.
1971      */
1972     private int peekPastLine() {
1973         int ch = temp[++cursor];
1974         while (ch != 0 && !isLineSeparator(ch))
1975             ch = temp[++cursor];
1976         return ch;
1977     }
1978 
1979     /**
1980      * Determines if character is a line separator in the current mode
1981      */
1982     private boolean isLineSeparator(int ch) {
1983         if (has(UNIX_LINES)) {
1984             return ch == '\n';
1985         } else {
1986             return (ch == '\n' ||
1987                     ch == '\r' ||
1988                     (ch|1) == '\u2029' ||
1989                     ch == '\u0085');
1990         }
1991     }
1992 
1993     /**
1994      * Read the character after the next one, and advance the cursor by two.
1995      */
1996     private int skip() {
1997         int i = cursor;
1998         int ch = temp[i+1];
1999         cursor = i + 2;
2000         return ch;
2001     }
2002 
2003     /**
2004      * Unread one next character, and retreat cursor by one.
2005      */
2006     private void unread() {
2007         cursor--;
2008     }
2009 
2010     /**
2011      * Internal method used for handling all syntax errors. The pattern is
2012      * displayed with a pointer to aid in locating the syntax error.
2013      */
2014     private PatternSyntaxException error(String s) {
2015         return new PatternSyntaxException(s, normalizedPattern,  cursor - 1);
2016     }
2017 
2018     /**
2019      * Determines if there is any supplementary character or unpaired
2020      * surrogate in the specified range.
2021      */
2022     private boolean findSupplementary(int start, int end) {
2023         for (int i = start; i < end; i++) {
2024             if (isSupplementary(temp[i]))
2025                 return true;
2026         }
2027         return false;
2028     }
2029 
2030     /**
2031      * Determines if the specified code point is a supplementary
2032      * character or unpaired surrogate.
2033      */
2034     private static final boolean isSupplementary(int ch) {
2035         return ch >= Character.MIN_SUPPLEMENTARY_CODE_POINT ||
2036                Character.isSurrogate((char)ch);
2037     }
2038 
2039     /**
2040      *  The following methods handle the main parsing. They are sorted
2041      *  according to their precedence order, the lowest one first.
2042      */
2043 
2044     /**
2045      * The expression is parsed with branch nodes added for alternations.
2046      * This may be called recursively to parse sub expressions that may
2047      * contain alternations.
2048      */
2049     private Node expr(Node end) {
2050         Node prev = null;
2051         Node firstTail = null;
2052         Branch branch = null;
2053         Node branchConn = null;
2054 
2055         for (;;) {
2056             Node node = sequence(end);
2057             Node nodeTail = root;      //double return
2058             if (prev == null) {
2059                 prev = node;
2060                 firstTail = nodeTail;
2061             } else {
2062                 // Branch
2063                 if (branchConn == null) {
2064                     branchConn = new BranchConn();
2065                     branchConn.next = end;
2066                 }
2067                 if (node == end) {
2068                     // if the node returned from sequence() is "end"
2069                     // we have an empty expr, set a null atom into
2070                     // the branch to indicate to go "next" directly.
2071                     node = null;
2072                 } else {
2073                     // the "tail.next" of each atom goes to branchConn
2074                     nodeTail.next = branchConn;
2075                 }
2076                 if (prev == branch) {
2077                     branch.add(node);
2078                 } else {
2079                     if (prev == end) {
2080                         prev = null;
2081                     } else {
2082                         // replace the "end" with "branchConn" at its tail.next
2083                         // when put the "prev" into the branch as the first atom.
2084                         firstTail.next = branchConn;
2085                     }
2086                     prev = branch = new Branch(prev, node, branchConn);
2087                 }
2088             }
2089             if (peek() != '|') {
2090                 return prev;
2091             }
2092             next();
2093         }
2094     }
2095 
2096     @SuppressWarnings("fallthrough")
2097     /**
2098      * Parsing of sequences between alternations.
2099      */
2100     private Node sequence(Node end) {
2101         Node head = null;
2102         Node tail = null;
2103         Node node;
2104     LOOP:
2105         for (;;) {
2106             int ch = peek();
2107             switch (ch) {
2108             case '(':
2109                 // Because group handles its own closure,
2110                 // we need to treat it differently
2111                 node = group0();
2112                 // Check for comment or flag group
2113                 if (node == null)
2114                     continue;
2115                 if (head == null)
2116                     head = node;
2117                 else
2118                     tail.next = node;
2119                 // Double return: Tail was returned in root
2120                 tail = root;
2121                 continue;
2122             case '[':
2123                 if (has(CANON_EQ) && !has(LITERAL))
2124                     node = new NFCCharProperty(clazz(true));
2125                 else
2126                     node = newCharProperty(clazz(true));
2127                 break;
2128             case '\\':
2129                 ch = nextEscaped();
2130                 if (ch == 'p' || ch == 'P') {
2131                     boolean oneLetter = true;
2132                     boolean comp = (ch == 'P');
2133                     ch = next(); // Consume { if present
2134                     if (ch != '{') {
2135                         unread();
2136                     } else {
2137                         oneLetter = false;
2138                     }
2139                     // node = newCharProperty(family(oneLetter, comp));
2140                     if (has(CANON_EQ) && !has(LITERAL))
2141                         node = new NFCCharProperty(family(oneLetter, comp));
2142                     else
2143                         node = newCharProperty(family(oneLetter, comp));
2144                 } else {
2145                     unread();
2146                     node = atom();
2147                 }
2148                 break;
2149             case '^':
2150                 next();
2151                 if (has(MULTILINE)) {
2152                     if (has(UNIX_LINES))
2153                         node = new UnixCaret();
2154                     else
2155                         node = new Caret();
2156                 } else {
2157                     node = new Begin();
2158                 }
2159                 break;
2160             case '$':
2161                 next();
2162                 if (has(UNIX_LINES))
2163                     node = new UnixDollar(has(MULTILINE));
2164                 else
2165                     node = new Dollar(has(MULTILINE));
2166                 break;
2167             case '.':
2168                 next();
2169                 if (has(DOTALL)) {
2170                     node = new CharProperty(ALL());
2171                 } else {
2172                     if (has(UNIX_LINES)) {
2173                         node = new CharProperty(UNIXDOT());
2174                     } else {
2175                         node = new CharProperty(DOT());
2176                     }
2177                 }
2178                 break;
2179             case '|':
2180             case ')':
2181                 break LOOP;
2182             case ']': // Now interpreting dangling ] and } as literals
2183             case '}':
2184                 node = atom();
2185                 break;
2186             case '?':
2187             case '*':
2188             case '+':
2189                 next();
2190                 throw error("Dangling meta character '" + ((char)ch) + "'");
2191             case 0:
2192                 if (cursor >= patternLength) {
2193                     break LOOP;
2194                 }
2195                 // Fall through
2196             default:
2197                 node = atom();
2198                 break;
2199             }
2200 
2201             node = closure(node);
2202             /* save the top dot-greedy nodes (.*, .+) as well
2203             if (node instanceof GreedyCharProperty &&
2204                 ((GreedyCharProperty)node).cp instanceof Dot) {
2205                 topClosureNodes.add(node);
2206             }
2207             */
2208             if (head == null) {
2209                 head = tail = node;
2210             } else {
2211                 tail.next = node;
2212                 tail = node;
2213             }
2214         }
2215         if (head == null) {
2216             return end;
2217         }
2218         tail.next = end;
2219         root = tail;      //double return
2220         return head;
2221     }
2222 
2223     @SuppressWarnings("fallthrough")
2224     /**
2225      * Parse and add a new Single or Slice.
2226      */
2227     private Node atom() {
2228         int first = 0;
2229         int prev = -1;
2230         boolean hasSupplementary = false;
2231         int ch = peek();
2232         for (;;) {
2233             switch (ch) {
2234             case '*':
2235             case '+':
2236             case '?':
2237             case '{':
2238                 if (first > 1) {
2239                     cursor = prev;    // Unwind one character
2240                     first--;
2241                 }
2242                 break;
2243             case '$':
2244             case '.':
2245             case '^':
2246             case '(':
2247             case '[':
2248             case '|':
2249             case ')':
2250                 break;
2251             case '\\':
2252                 ch = nextEscaped();
2253                 if (ch == 'p' || ch == 'P') { // Property
2254                     if (first > 0) { // Slice is waiting; handle it first
2255                         unread();
2256                         break;
2257                     } else { // No slice; just return the family node
2258                         boolean comp = (ch == 'P');
2259                         boolean oneLetter = true;
2260                         ch = next(); // Consume { if present
2261                         if (ch != '{')
2262                             unread();
2263                         else
2264                             oneLetter = false;
2265                         if (has(CANON_EQ) && !has(LITERAL))
2266                             return new NFCCharProperty(family(oneLetter, comp));
2267                         else
2268                             return newCharProperty(family(oneLetter, comp));
2269                     }
2270                 }
2271                 unread();
2272                 prev = cursor;
2273                 ch = escape(false, first == 0, false);
2274                 if (ch >= 0) {
2275                     append(ch, first);
2276                     first++;
2277                     if (isSupplementary(ch)) {
2278                         hasSupplementary = true;
2279                     }
2280                     ch = peek();
2281                     continue;
2282                 } else if (first == 0) {
2283                     return root;
2284                 }
2285                 // Unwind meta escape sequence
2286                 cursor = prev;
2287                 break;
2288             case 0:
2289                 if (cursor >= patternLength) {
2290                     break;
2291                 }
2292                 // Fall through
2293             default:
2294                 prev = cursor;
2295                 append(ch, first);
2296                 first++;
2297                 if (isSupplementary(ch)) {
2298                     hasSupplementary = true;
2299                 }
2300                 ch = next();
2301                 continue;
2302             }
2303             break;
2304         }
2305         if (first == 1) {
2306             return newCharProperty(single(buffer[0]));
2307         } else {
2308             return newSlice(buffer, first, hasSupplementary);
2309         }
2310     }
2311 
2312     private void append(int ch, int index) {
2313         int len = buffer.length;
2314         if (index - len >= 0) {
2315             len = ArraysSupport.newLength(len,
2316                     1 + index - len, /* minimum growth */
2317                     len              /* preferred growth */);
2318             buffer = Arrays.copyOf(buffer, len);
2319         }
2320         buffer[index] = ch;
2321     }
2322 
2323     /**
2324      * Parses a backref greedily, taking as many numbers as it
2325      * can. The first digit is always treated as a backref, but
2326      * multi digit numbers are only treated as a backref if at
2327      * least that many backrefs exist at this point in the regex.
2328      */
2329     private Node ref(int refNum) {
2330         boolean done = false;
2331         while(!done) {
2332             int ch = peek();
2333             switch(ch) {
2334             case '0':
2335             case '1':
2336             case '2':
2337             case '3':
2338             case '4':
2339             case '5':
2340             case '6':
2341             case '7':
2342             case '8':
2343             case '9':
2344                 int newRefNum = (refNum * 10) + (ch - '0');
2345                 // Add another number if it doesn't make a group
2346                 // that doesn't exist
2347                 if (capturingGroupCount - 1 < newRefNum) {
2348                     done = true;
2349                     break;
2350                 }
2351                 refNum = newRefNum;
2352                 read();
2353                 break;
2354             default:
2355                 done = true;
2356                 break;
2357             }
2358         }
2359         hasGroupRef = true;
2360         if (has(CASE_INSENSITIVE))
2361             return new CIBackRef(refNum, has(UNICODE_CASE));
2362         else
2363             return new BackRef(refNum);
2364     }
2365 
2366     /**
2367      * Parses an escape sequence to determine the actual value that needs
2368      * to be matched.
2369      * If -1 is returned and create was true a new object was added to the tree
2370      * to handle the escape sequence.
2371      * If the returned value is greater than zero, it is the value that
2372      * matches the escape sequence.
2373      */
2374     private int escape(boolean inclass, boolean create, boolean isrange) {
2375         int ch = skip();
2376         switch (ch) {
2377         case '0':
2378             return o();
2379         case '1':
2380         case '2':
2381         case '3':
2382         case '4':
2383         case '5':
2384         case '6':
2385         case '7':
2386         case '8':
2387         case '9':
2388             if (inclass) break;
2389             if (create) {
2390                 root = ref((ch - '0'));
2391             }
2392             return -1;
2393         case 'A':
2394             if (inclass) break;
2395             if (create) root = new Begin();
2396             return -1;
2397         case 'B':
2398             if (inclass) break;
2399             if (create) root = new Bound(Bound.NONE, has(UNICODE_CHARACTER_CLASS));
2400             return -1;
2401         case 'C':
2402             break;
2403         case 'D':
2404             if (create) {
2405                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2406                             CharPredicates.DIGIT() : CharPredicates.ASCII_DIGIT();
2407                 predicate = predicate.negate();
2408                 if (!inclass)
2409                     root = newCharProperty(predicate);
2410             }
2411             return -1;
2412         case 'E':
2413         case 'F':
2414             break;
2415         case 'G':
2416             if (inclass) break;
2417             if (create) root = new LastMatch();
2418             return -1;
2419         case 'H':
2420             if (create) {
2421                 predicate = HorizWS().negate();
2422                 if (!inclass)
2423                     root = newCharProperty(predicate);
2424             }
2425             return -1;
2426         case 'I':
2427         case 'J':
2428         case 'K':
2429         case 'L':
2430         case 'M':
2431             break;
2432         case 'N':
2433             return N();
2434         case 'O':
2435         case 'P':
2436         case 'Q':
2437             break;
2438         case 'R':
2439             if (inclass) break;
2440             if (create) root = new LineEnding();
2441             return -1;
2442         case 'S':
2443             if (create) {
2444                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2445                             CharPredicates.WHITE_SPACE() : CharPredicates.ASCII_SPACE();
2446                 predicate = predicate.negate();
2447                 if (!inclass)
2448                     root = newCharProperty(predicate);
2449             }
2450             return -1;
2451         case 'T':
2452         case 'U':
2453             break;
2454         case 'V':
2455             if (create) {
2456                 predicate = VertWS().negate();
2457                 if (!inclass)
2458                     root = newCharProperty(predicate);
2459             }
2460             return -1;
2461         case 'W':
2462             if (create) {
2463                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2464                             CharPredicates.WORD() : CharPredicates.ASCII_WORD();
2465                 predicate = predicate.negate();
2466                 if (!inclass)
2467                     root = newCharProperty(predicate);
2468             }
2469             return -1;
2470         case 'X':
2471             if (inclass) break;
2472             if (create) {
2473                 root = new XGrapheme();
2474             }
2475             return -1;
2476         case 'Y':
2477             break;
2478         case 'Z':
2479             if (inclass) break;
2480             if (create) {
2481                 if (has(UNIX_LINES))
2482                     root = new UnixDollar(false);
2483                 else
2484                     root = new Dollar(false);
2485             }
2486             return -1;
2487         case 'a':
2488             return '\007';
2489         case 'b':
2490             if (inclass) break;
2491             if (create) {
2492                 if (peek() == '{') {
2493                     if (skip() == 'g') {
2494                         if (read() == '}') {
2495                             root = new GraphemeBound();
2496                             return -1;
2497                         }
2498                         break;  // error missing trailing }
2499                     }
2500                     unread(); unread();
2501                 }
2502                 root = new Bound(Bound.BOTH, has(UNICODE_CHARACTER_CLASS));
2503             }
2504             return -1;
2505         case 'c':
2506             return c();
2507         case 'd':
2508             if (create) {
2509                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2510                             CharPredicates.DIGIT() : CharPredicates.ASCII_DIGIT();
2511                 if (!inclass)
2512                     root = newCharProperty(predicate);
2513             }
2514             return -1;
2515         case 'e':
2516             return '\033';
2517         case 'f':
2518             return '\f';
2519         case 'g':
2520             break;
2521         case 'h':
2522             if (create) {
2523                 predicate = HorizWS();
2524                 if (!inclass)
2525                     root = newCharProperty(predicate);
2526             }
2527             return -1;
2528         case 'i':
2529         case 'j':
2530             break;
2531         case 'k':
2532             if (inclass)
2533                 break;
2534             if (read() != '<')
2535                 throw error("\\k is not followed by '<' for named capturing group");
2536             String name = groupname(read());
2537             if (!namedGroups().containsKey(name))
2538                 throw error("named capturing group <" + name + "> does not exist");
2539             if (create) {
2540                 hasGroupRef = true;
2541                 if (has(CASE_INSENSITIVE))
2542                     root = new CIBackRef(namedGroups().get(name), has(UNICODE_CASE));
2543                 else
2544                     root = new BackRef(namedGroups().get(name));
2545             }
2546             return -1;
2547         case 'l':
2548         case 'm':
2549             break;
2550         case 'n':
2551             return '\n';
2552         case 'o':
2553         case 'p':
2554         case 'q':
2555             break;
2556         case 'r':
2557             return '\r';
2558         case 's':
2559             if (create) {
2560                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2561                             CharPredicates.WHITE_SPACE() : CharPredicates.ASCII_SPACE();
2562                 if (!inclass)
2563                     root = newCharProperty(predicate);
2564             }
2565             return -1;
2566         case 't':
2567             return '\t';
2568         case 'u':
2569             return u();
2570         case 'v':
2571             // '\v' was implemented as VT/0x0B in releases < 1.8 (though
2572             // undocumented). In JDK8 '\v' is specified as a predefined
2573             // character class for all vertical whitespace characters.
2574             // So [-1, root=VertWS node] pair is returned (instead of a
2575             // single 0x0B). This breaks the range if '\v' is used as
2576             // the start or end value, such as [\v-...] or [...-\v], in
2577             // which a single definite value (0x0B) is expected. For
2578             // compatibility concern '\013'/0x0B is returned if isrange.
2579             if (isrange)
2580                 return '\013';
2581             if (create) {
2582                 predicate = VertWS();
2583                 if (!inclass)
2584                     root = newCharProperty(predicate);
2585             }
2586             return -1;
2587         case 'w':
2588             if (create) {
2589                 predicate = has(UNICODE_CHARACTER_CLASS) ?
2590                             CharPredicates.WORD() : CharPredicates.ASCII_WORD();
2591                 if (!inclass)
2592                     root = newCharProperty(predicate);
2593             }
2594             return -1;
2595         case 'x':
2596             return x();
2597         case 'y':
2598             break;
2599         case 'z':
2600             if (inclass) break;
2601             if (create) root = new End();
2602             return -1;
2603         default:
2604             return ch;
2605         }
2606         throw error("Illegal/unsupported escape sequence");
2607     }
2608 
2609     /**
2610      * Parse a character class, and return the node that matches it.
2611      *
2612      * Consumes a ] on the way out if consume is true. Usually consume
2613      * is true except for the case of [abc&&def] where def is a separate
2614      * right hand node with "understood" brackets.
2615      */
2616     private CharPredicate clazz(boolean consume) {
2617         CharPredicate prev = null;
2618         CharPredicate curr = null;
2619         BitClass bits = new BitClass();
2620 
2621         boolean isNeg = false;
2622         boolean hasBits = false;
2623         int ch = next();
2624 
2625         // Negates if first char in a class, otherwise literal
2626         if (ch == '^' && temp[cursor-1] == '[') {
2627             ch = next();
2628             isNeg = true;
2629         }
2630         for (;;) {
2631             switch (ch) {
2632                 case '[':
2633                     curr = clazz(true);
2634                     if (prev == null)
2635                         prev = curr;
2636                     else
2637                         prev = prev.union(curr);
2638                     ch = peek();
2639                     continue;
2640                 case '&':
2641                     ch = next();
2642                     if (ch == '&') {
2643                         ch = next();
2644                         CharPredicate right = null;
2645                         while (ch != ']' && ch != '&') {
2646                             if (ch == '[') {
2647                                 if (right == null)
2648                                     right = clazz(true);
2649                                 else
2650                                     right = right.union(clazz(true));
2651                             } else { // abc&&def
2652                                 unread();
2653                                 right = clazz(false);
2654                             }
2655                             ch = peek();
2656                         }
2657                         if (hasBits) {
2658                             // bits used, union has high precedence
2659                             if (prev == null) {
2660                                 prev = curr = bits;
2661                             } else {
2662                                 prev = prev.union(bits);
2663                             }
2664                             hasBits = false;
2665                         }
2666                         if (right != null)
2667                             curr = right;
2668                         if (prev == null) {
2669                             if (right == null)
2670                                 throw error("Bad class syntax");
2671                             else
2672                                 prev = right;
2673                         } else {
2674                             prev = prev.and(curr);
2675                         }
2676                     } else {
2677                         // treat as a literal &
2678                         unread();
2679                         break;
2680                     }
2681                     continue;
2682                 case 0:
2683                     if (cursor >= patternLength)
2684                         throw error("Unclosed character class");
2685                     break;
2686                 case ']':
2687                     if (prev != null || hasBits) {
2688                         if (consume)
2689                             next();
2690                         if (prev == null)
2691                             prev = bits;
2692                         else if (hasBits)
2693                             prev = prev.union(bits);
2694                         if (isNeg)
2695                             return prev.negate();
2696                         return prev;
2697                     }
2698                     break;
2699                 default:
2700                     break;
2701             }
2702             curr = range(bits);
2703             if (curr == null) {    // the bits used
2704                 hasBits = true;
2705             } else {
2706                 if (prev == null)
2707                     prev = curr;
2708                 else if (prev != curr)
2709                     prev = prev.union(curr);
2710             }
2711             ch = peek();
2712         }
2713     }
2714 
2715     private CharPredicate bitsOrSingle(BitClass bits, int ch) {
2716         /* Bits can only handle codepoints in [u+0000-u+00ff] range.
2717            Use "single" node instead of bits when dealing with unicode
2718            case folding for codepoints listed below.
2719            (1)Uppercase out of range: u+00ff, u+00b5
2720               toUpperCase(u+00ff) -> u+0178
2721               toUpperCase(u+00b5) -> u+039c
2722            (2)LatinSmallLetterLongS u+17f
2723               toUpperCase(u+017f) -> u+0053
2724            (3)LatinSmallLetterDotlessI u+131
2725               toUpperCase(u+0131) -> u+0049
2726            (4)LatinCapitalLetterIWithDotAbove u+0130
2727               toLowerCase(u+0130) -> u+0069
2728            (5)KelvinSign u+212a
2729               toLowerCase(u+212a) ==> u+006B
2730            (6)AngstromSign u+212b
2731               toLowerCase(u+212b) ==> u+00e5
2732         */
2733         if (ch < 256 &&
2734             !(has(CASE_INSENSITIVE) && has(UNICODE_CASE) &&
2735               (ch == 0xff || ch == 0xb5 ||
2736                ch == 0x49 || ch == 0x69 ||    //I and i
2737                ch == 0x53 || ch == 0x73 ||    //S and s
2738                ch == 0x4b || ch == 0x6b ||    //K and k
2739                ch == 0xc5 || ch == 0xe5))) {  //A+ring
2740             bits.add(ch, flags0);
2741             return null;
2742         }
2743         return single(ch);
2744     }
2745 
2746     /**
2747      *  Returns a suitably optimized, single character predicate
2748      */
2749     private CharPredicate single(final int ch) {
2750         if (has(CASE_INSENSITIVE)) {
2751             int lower, upper;
2752             if (has(UNICODE_CASE)) {
2753                 upper = Character.toUpperCase(ch);
2754                 lower = Character.toLowerCase(upper);
2755                 // Unicode case insensitive matches
2756                 if (upper != lower)
2757                     return SingleU(lower);
2758             } else if (ASCII.isAscii(ch)) {
2759                 lower = ASCII.toLower(ch);
2760                 upper = ASCII.toUpper(ch);
2761                 // Case insensitive matches a given BMP character
2762                 if (lower != upper)
2763                     return SingleI(lower, upper);
2764             }
2765         }
2766         if (isSupplementary(ch))
2767             return SingleS(ch);
2768         return Single(ch);  // Match a given BMP character
2769     }
2770 
2771     /**
2772      * Parse a single character or a character range in a character class
2773      * and return its representative node.
2774      */
2775     private CharPredicate range(BitClass bits) {
2776         int ch = peek();
2777         if (ch == '\\') {
2778             ch = nextEscaped();
2779             if (ch == 'p' || ch == 'P') { // A property
2780                 boolean comp = (ch == 'P');
2781                 boolean oneLetter = true;
2782                 // Consume { if present
2783                 ch = next();
2784                 if (ch != '{')
2785                     unread();
2786                 else
2787                     oneLetter = false;
2788                 return family(oneLetter, comp);
2789             } else { // ordinary escape
2790                 boolean isrange = temp[cursor+1] == '-';
2791                 unread();
2792                 ch = escape(true, true, isrange);
2793                 if (ch == -1)
2794                     return predicate;
2795             }
2796         } else {
2797             next();
2798         }
2799         if (ch >= 0) {
2800             if (peek() == '-') {
2801                 int endRange = temp[cursor+1];
2802                 if (endRange == '[') {
2803                     return bitsOrSingle(bits, ch);
2804                 }
2805                 if (endRange != ']') {
2806                     next();
2807                     int m = peek();
2808                     if (m == '\\') {
2809                         m = escape(true, false, true);
2810                     } else {
2811                         next();
2812                     }
2813                     if (m < ch) {
2814                         throw error("Illegal character range");
2815                     }
2816                     if (has(CASE_INSENSITIVE)) {
2817                         if (has(UNICODE_CASE))
2818                             return CIRangeU(ch, m);
2819                         return CIRange(ch, m);
2820                     } else {
2821                         return Range(ch, m);
2822                     }
2823                 }
2824             }
2825             return bitsOrSingle(bits, ch);
2826         }
2827         throw error("Unexpected character '"+((char)ch)+"'");
2828     }
2829 
2830     /**
2831      * Parses a Unicode character family and returns its representative node.
2832      */
2833     private CharPredicate family(boolean singleLetter, boolean isComplement) {
2834         next();
2835         String name;
2836         CharPredicate p = null;
2837 
2838         if (singleLetter) {
2839             int c = temp[cursor];
2840             if (!Character.isSupplementaryCodePoint(c)) {
2841                 name = String.valueOf((char)c);
2842             } else {
2843                 name = new String(temp, cursor, 1);
2844             }
2845             read();
2846         } else {
2847             int i = cursor;
2848             mark('}');
2849             while(read() != '}') {
2850             }
2851             mark('\000');
2852             int j = cursor;
2853             if (j > patternLength)
2854                 throw error("Unclosed character family");
2855             if (i + 1 >= j)
2856                 throw error("Empty character family");
2857             name = new String(temp, i, j-i-1);
2858         }
2859 
2860         int i = name.indexOf('=');
2861         if (i != -1) {
2862             // property construct \p{name=value}
2863             String value = name.substring(i + 1);
2864             name = name.substring(0, i).toLowerCase(Locale.ENGLISH);
2865             switch (name) {
2866                 case "sc":
2867                 case "script":
2868                     p = CharPredicates.forUnicodeScript(value);
2869                     break;
2870                 case "blk":
2871                 case "block":
2872                     p = CharPredicates.forUnicodeBlock(value);
2873                     break;
2874                 case "gc":
2875                 case "general_category":
2876                     p = CharPredicates.forProperty(value);
2877                     break;
2878                 default:
2879                     break;
2880             }
2881             if (p == null)
2882                 throw error("Unknown Unicode property {name=<" + name + ">, "
2883                              + "value=<" + value + ">}");
2884 
2885         } else {
2886             if (name.startsWith("In")) {
2887                 // \p{InBlockName}
2888                 p = CharPredicates.forUnicodeBlock(name.substring(2));
2889             } else if (name.startsWith("Is")) {
2890                 // \p{IsGeneralCategory} and \p{IsScriptName}
2891                 name = name.substring(2);
2892                 p = CharPredicates.forUnicodeProperty(name);
2893                 if (p == null)
2894                     p = CharPredicates.forProperty(name);
2895                 if (p == null)
2896                     p = CharPredicates.forUnicodeScript(name);
2897             } else {
2898                 if (has(UNICODE_CHARACTER_CLASS)) {
2899                     p = CharPredicates.forPOSIXName(name);
2900                 }
2901                 if (p == null)
2902                     p = CharPredicates.forProperty(name);
2903             }
2904             if (p == null)
2905                 throw error("Unknown character property name {In/Is" + name + "}");
2906         }
2907         if (isComplement) {
2908             // it might be too expensive to detect if a complement of
2909             // CharProperty can match "certain" supplementary. So just
2910             // go with StartS.
2911             hasSupplementary = true;
2912             p = p.negate();
2913         }
2914         return p;
2915     }
2916 
2917     private CharProperty newCharProperty(CharPredicate p) {
2918         if (p == null)
2919             return null;
2920         if (p instanceof BmpCharPredicate)
2921             return new BmpCharProperty((BmpCharPredicate)p);
2922         else
2923             return new CharProperty(p);
2924     }
2925 
2926     /**
2927      * Parses and returns the name of a "named capturing group", the trailing
2928      * ">" is consumed after parsing.
2929      */
2930     private String groupname(int ch) {
2931         StringBuilder sb = new StringBuilder();
2932         if (!ASCII.isAlpha(ch))
2933             throw error("capturing group name does not start with a Latin letter");
2934         do {
2935             sb.append((char) ch);
2936         } while (ASCII.isAlnum(ch=read()));
2937         if (ch != '>')
2938             throw error("named capturing group is missing trailing '>'");
2939         return sb.toString();
2940     }
2941 
2942     /**
2943      * Parses a group and returns the head node of a set of nodes that process
2944      * the group. Sometimes a double return system is used where the tail is
2945      * returned in root.
2946      */
2947     private Node group0() {
2948         boolean capturingGroup = false;
2949         Node head;
2950         Node tail;
2951         int save = flags0;
2952         int saveTCNCount = topClosureNodes.size();
2953         root = null;
2954         int ch = next();
2955         if (ch == '?') {
2956             ch = skip();
2957             switch (ch) {
2958             case ':':   //  (?:xxx) pure group
2959                 head = createGroup(true);
2960                 tail = root;
2961                 head.next = expr(tail);
2962                 break;
2963             case '=':   // (?=xxx) and (?!xxx) lookahead
2964             case '!':
2965                 head = createGroup(true);
2966                 tail = root;
2967                 head.next = expr(tail);
2968                 if (ch == '=') {
2969                     head = tail = new Pos(head);
2970                 } else {
2971                     head = tail = new Neg(head);
2972                 }
2973                 break;
2974             case '>':   // (?>xxx)  independent group
2975                 head = createGroup(true);
2976                 tail = root;
2977                 head.next = expr(tail);
2978                 head = tail = new Ques(head, Qtype.INDEPENDENT);
2979                 break;
2980             case '<':   // (?<xxx)  look behind
2981                 ch = read();
2982                 if (ch != '=' && ch != '!') {
2983                     // named captured group
2984                     String name = groupname(ch);
2985                     if (namedGroups().containsKey(name))
2986                         throw error("Named capturing group <" + name
2987                                     + "> is already defined");
2988                     capturingGroup = true;
2989                     head = createGroup(false);
2990                     tail = root;
2991                     namedGroups().put(name, capturingGroupCount-1);
2992                     head.next = expr(tail);
2993                     break;
2994                 }
2995                 int start = cursor;
2996                 head = createGroup(true);
2997                 tail = root;
2998                 head.next = expr(tail);
2999                 tail.next = LookBehindEndNode.INSTANCE;
3000                 TreeInfo info = new TreeInfo();
3001                 head.study(info);
3002                 if (info.maxValid == false) {
3003                     throw error("Look-behind group does not have "
3004                                 + "an obvious maximum length");
3005                 }
3006                 boolean hasSupplementary = findSupplementary(start, patternLength);
3007                 if (ch == '=') {
3008                     head = tail = (hasSupplementary ?
3009                                    new BehindS(head, info.maxLength,
3010                                                info.minLength) :
3011                                    new Behind(head, info.maxLength,
3012                                               info.minLength));
3013                 } else { // if (ch == '!')
3014                     head = tail = (hasSupplementary ?
3015                                    new NotBehindS(head, info.maxLength,
3016                                                   info.minLength) :
3017                                    new NotBehind(head, info.maxLength,
3018                                                  info.minLength));
3019                 }
3020                 // clear all top-closure-nodes inside lookbehind
3021                 if (saveTCNCount < topClosureNodes.size())
3022                     topClosureNodes.subList(saveTCNCount, topClosureNodes.size()).clear();
3023                 break;
3024             case '$':
3025             case '@':
3026                 throw error("Unknown group type");
3027             default:    // (?xxx:) inlined match flags
3028                 unread();
3029                 addFlag();
3030                 ch = read();
3031                 if (ch == ')') {
3032                     return null;    // Inline modifier only
3033                 }
3034                 if (ch != ':') {
3035                     throw error("Unknown inline modifier");
3036                 }
3037                 head = createGroup(true);
3038                 tail = root;
3039                 head.next = expr(tail);
3040                 break;
3041             }
3042         } else { // (xxx) a regular group
3043             capturingGroup = true;
3044             head = createGroup(false);
3045             tail = root;
3046             head.next = expr(tail);
3047         }
3048 
3049         accept(')', "Unclosed group");
3050         flags0 = save;
3051 
3052         // Check for quantifiers
3053         Node node = closure(head);
3054         if (node == head) { // No closure
3055             root = tail;
3056             return node;    // Dual return
3057         }
3058         if (head == tail) { // Zero length assertion
3059             root = node;
3060             return node;    // Dual return
3061         }
3062 
3063         // have group closure, clear all inner closure nodes from the
3064         // top list (no backtracking stopper optimization for inner
3065         if (saveTCNCount < topClosureNodes.size())
3066             topClosureNodes.subList(saveTCNCount, topClosureNodes.size()).clear();
3067 
3068         if (node instanceof Ques) {
3069             Ques ques = (Ques) node;
3070             if (ques.type == Qtype.POSSESSIVE) {
3071                 root = node;
3072                 return node;
3073             }
3074             tail.next = new BranchConn();
3075             tail = tail.next;
3076             if (ques.type == Qtype.GREEDY) {
3077                 head = new Branch(head, null, tail);
3078             } else { // Reluctant quantifier
3079                 head = new Branch(null, head, tail);
3080             }
3081             root = tail;
3082             return head;
3083         } else if (node instanceof Curly) {
3084             Curly curly = (Curly) node;
3085             if (curly.type == Qtype.POSSESSIVE) {
3086                 root = node;
3087                 return node;
3088             }
3089             // Discover if the group is deterministic
3090             TreeInfo info = new TreeInfo();
3091             if (head.study(info)) { // Deterministic
3092                 GroupTail temp = (GroupTail) tail;
3093                 head = root = new GroupCurly(head.next, curly.cmin,
3094                                    curly.cmax, curly.type,
3095                                    ((GroupTail)tail).localIndex,
3096                                    ((GroupTail)tail).groupIndex,
3097                                              capturingGroup);
3098                 return head;
3099             } else { // Non-deterministic
3100                 int temp = ((GroupHead) head).localIndex;
3101                 Loop loop;
3102                 if (curly.type == Qtype.GREEDY) {
3103                     loop = new Loop(this.localCount, temp);
3104                     // add the max_reps greedy to the top-closure-node list
3105                     if (curly.cmax == MAX_REPS)
3106                         topClosureNodes.add(loop);
3107                 } else {  // Reluctant Curly
3108                     loop = new LazyLoop(this.localCount, temp);
3109                 }
3110                 Prolog prolog = new Prolog(loop);
3111                 this.localCount += 1;
3112                 loop.cmin = curly.cmin;
3113                 loop.cmax = curly.cmax;
3114                 loop.body = head;
3115                 tail.next = loop;
3116                 root = loop;
3117                 return prolog; // Dual return
3118             }
3119         }
3120         throw error("Internal logic error");
3121     }
3122 
3123     /**
3124      * Create group head and tail nodes using double return. If the group is
3125      * created with anonymous true then it is a pure group and should not
3126      * affect group counting.
3127      */
3128     private Node createGroup(boolean anonymous) {
3129         int localIndex = localCount++;
3130         int groupIndex = 0;
3131         if (!anonymous)
3132             groupIndex = capturingGroupCount++;
3133         GroupHead head = new GroupHead(localIndex);
3134         root = new GroupTail(localIndex, groupIndex);
3135 
3136         // for debug/print only, head.match does NOT need the "tail" info
3137         head.tail = (GroupTail)root;
3138 
3139         if (!anonymous && groupIndex < 10)
3140             groupNodes[groupIndex] = head;
3141         return head;
3142     }
3143 
3144     @SuppressWarnings("fallthrough")
3145     /**
3146      * Parses inlined match flags and set them appropriately.
3147      */
3148     private void addFlag() {
3149         int ch = peek();
3150         for (;;) {
3151             switch (ch) {
3152             case 'i':
3153                 flags0 |= CASE_INSENSITIVE;
3154                 break;
3155             case 'm':
3156                 flags0 |= MULTILINE;
3157                 break;
3158             case 's':
3159                 flags0 |= DOTALL;
3160                 break;
3161             case 'd':
3162                 flags0 |= UNIX_LINES;
3163                 break;
3164             case 'u':
3165                 flags0 |= UNICODE_CASE;
3166                 break;
3167             case 'c':
3168                 flags0 |= CANON_EQ;
3169                 break;
3170             case 'x':
3171                 flags0 |= COMMENTS;
3172                 break;
3173             case 'U':
3174                 flags0 |= (UNICODE_CHARACTER_CLASS | UNICODE_CASE);
3175                 break;
3176             case '-': // subFlag then fall through
3177                 ch = next();
3178                 subFlag();
3179             default:
3180                 return;
3181             }
3182             ch = next();
3183         }
3184     }
3185 
3186     @SuppressWarnings("fallthrough")
3187     /**
3188      * Parses the second part of inlined match flags and turns off
3189      * flags appropriately.
3190      */
3191     private void subFlag() {
3192         int ch = peek();
3193         for (;;) {
3194             switch (ch) {
3195             case 'i':
3196                 flags0 &= ~CASE_INSENSITIVE;
3197                 break;
3198             case 'm':
3199                 flags0 &= ~MULTILINE;
3200                 break;
3201             case 's':
3202                 flags0 &= ~DOTALL;
3203                 break;
3204             case 'd':
3205                 flags0 &= ~UNIX_LINES;
3206                 break;
3207             case 'u':
3208                 flags0 &= ~UNICODE_CASE;
3209                 break;
3210             case 'c':
3211                 flags0 &= ~CANON_EQ;
3212                 break;
3213             case 'x':
3214                 flags0 &= ~COMMENTS;
3215                 break;
3216             case 'U':
3217                 flags0 &= ~(UNICODE_CHARACTER_CLASS | UNICODE_CASE);
3218                 break;
3219             default:
3220                 return;
3221             }
3222             ch = next();
3223         }
3224     }
3225 
3226     static final int MAX_REPS   = 0x7FFFFFFF;
3227 
3228     static enum Qtype {
3229         GREEDY, LAZY, POSSESSIVE, INDEPENDENT
3230     }
3231 
3232     private Node curly(Node prev, int cmin) {
3233         int ch = next();
3234         if (ch == '?') {
3235             next();
3236             return new Curly(prev, cmin, MAX_REPS, Qtype.LAZY);
3237         } else if (ch == '+') {
3238             next();
3239             return new Curly(prev, cmin, MAX_REPS, Qtype.POSSESSIVE);
3240         }
3241         if (prev instanceof BmpCharProperty) {
3242             return new BmpCharPropertyGreedy((BmpCharProperty)prev, cmin);
3243         } else if (prev instanceof CharProperty) {
3244             return new CharPropertyGreedy((CharProperty)prev, cmin);
3245         }
3246         return new Curly(prev, cmin, MAX_REPS, Qtype.GREEDY);
3247     }
3248 
3249     /**
3250      * Processes repetition. If the next character peeked is a quantifier
3251      * then new nodes must be appended to handle the repetition.
3252      * Prev could be a single or a group, so it could be a chain of nodes.
3253      */
3254     private Node closure(Node prev) {
3255         int ch = peek();
3256         switch (ch) {
3257         case '?':
3258             ch = next();
3259             if (ch == '?') {
3260                 next();
3261                 return new Ques(prev, Qtype.LAZY);
3262             } else if (ch == '+') {
3263                 next();
3264                 return new Ques(prev, Qtype.POSSESSIVE);
3265             }
3266             return new Ques(prev, Qtype.GREEDY);
3267         case '*':
3268             return curly(prev, 0);
3269         case '+':
3270             return curly(prev, 1);
3271         case '{':
3272             ch = skip();
3273             if (ASCII.isDigit(ch)) {
3274                 int cmin = 0, cmax;
3275                 try {
3276                     do {
3277                         cmin = Math.addExact(Math.multiplyExact(cmin, 10),
3278                                              ch - '0');
3279                     } while (ASCII.isDigit(ch = read()));
3280                     if (ch == ',') {
3281                         ch = read();
3282                         if (ch == '}') {
3283                             unread();
3284                             return curly(prev, cmin);
3285                         } else {
3286                             cmax = 0;
3287                             while (ASCII.isDigit(ch)) {
3288                                 cmax = Math.addExact(Math.multiplyExact(cmax, 10),
3289                                                      ch - '0');
3290                                 ch = read();
3291                             }
3292                         }
3293                     } else {
3294                         cmax = cmin;
3295                     }
3296                 } catch (ArithmeticException ae) {
3297                     throw error("Illegal repetition range");
3298                 }
3299                 if (ch != '}')
3300                     throw error("Unclosed counted closure");
3301                 if (cmax < cmin)
3302                     throw error("Illegal repetition range");
3303                 ch = peek();
3304                 if (ch == '?') {
3305                     next();
3306                     return new Curly(prev, cmin, cmax, Qtype.LAZY);
3307                 } else if (ch == '+') {
3308                     next();
3309                     return new Curly(prev, cmin, cmax, Qtype.POSSESSIVE);
3310                 } else {
3311                     return new Curly(prev, cmin, cmax, Qtype.GREEDY);
3312                 }
3313             } else {
3314                 throw error("Illegal repetition");
3315             }
3316         default:
3317             return prev;
3318         }
3319     }
3320 
3321     /**
3322      *  Utility method for parsing control escape sequences.
3323      */
3324     private int c() {
3325         if (cursor < patternLength) {
3326             return read() ^ 64;
3327         }
3328         throw error("Illegal control escape sequence");
3329     }
3330 
3331     /**
3332      *  Utility method for parsing octal escape sequences.
3333      */
3334     private int o() {
3335         int n = read();
3336         if (((n-'0')|('7'-n)) >= 0) {
3337             int m = read();
3338             if (((m-'0')|('7'-m)) >= 0) {
3339                 int o = read();
3340                 if ((((o-'0')|('7'-o)) >= 0) && (((n-'0')|('3'-n)) >= 0)) {
3341                     return (n - '0') * 64 + (m - '0') * 8 + (o - '0');
3342                 }
3343                 unread();
3344                 return (n - '0') * 8 + (m - '0');
3345             }
3346             unread();
3347             return (n - '0');
3348         }
3349         throw error("Illegal octal escape sequence");
3350     }
3351 
3352     /**
3353      *  Utility method for parsing hexadecimal escape sequences.
3354      */
3355     private int x() {
3356         int n = read();
3357         if (ASCII.isHexDigit(n)) {
3358             int m = read();
3359             if (ASCII.isHexDigit(m)) {
3360                 return ASCII.toDigit(n) * 16 + ASCII.toDigit(m);
3361             }
3362         } else if (n == '{' && ASCII.isHexDigit(peek())) {
3363             int ch = 0;
3364             while (ASCII.isHexDigit(n = read())) {
3365                 ch = (ch << 4) + ASCII.toDigit(n);
3366                 if (ch > Character.MAX_CODE_POINT)
3367                     throw error("Hexadecimal codepoint is too big");
3368             }
3369             if (n != '}')
3370                 throw error("Unclosed hexadecimal escape sequence");
3371             return ch;
3372         }
3373         throw error("Illegal hexadecimal escape sequence");
3374     }
3375 
3376     /**
3377      *  Utility method for parsing unicode escape sequences.
3378      */
3379     private int cursor() {
3380         return cursor;
3381     }
3382 
3383     private void setcursor(int pos) {
3384         cursor = pos;
3385     }
3386 
3387     private int uxxxx() {
3388         int n = 0;
3389         for (int i = 0; i < 4; i++) {
3390             int ch = read();
3391             if (!ASCII.isHexDigit(ch)) {
3392                 throw error("Illegal Unicode escape sequence");
3393             }
3394             n = n * 16 + ASCII.toDigit(ch);
3395         }
3396         return n;
3397     }
3398 
3399     private int u() {
3400         int n = uxxxx();
3401         if (Character.isHighSurrogate((char)n)) {
3402             int cur = cursor();
3403             if (read() == '\\' && read() == 'u') {
3404                 int n2 = uxxxx();
3405                 if (Character.isLowSurrogate((char)n2))
3406                     return Character.toCodePoint((char)n, (char)n2);
3407             }
3408             setcursor(cur);
3409         }
3410         return n;
3411     }
3412 
3413     private int N() {
3414         if (read() == '{') {
3415             int i = cursor;
3416             while (cursor < patternLength && read() != '}') {}
3417             if (cursor > patternLength)
3418                 throw error("Unclosed character name escape sequence");
3419             String name = new String(temp, i, cursor - i - 1);
3420             try {
3421                 return Character.codePointOf(name);
3422             } catch (IllegalArgumentException x) {
3423                 throw error("Unknown character name [" + name + "]");
3424             }
3425         }
3426         throw error("Illegal character name escape sequence");
3427     }
3428 
3429     //
3430     // Utility methods for code point support
3431     //
3432     private static final int countChars(CharSequence seq, int index,
3433                                         int lengthInCodePoints) {
3434         // optimization
3435         if (lengthInCodePoints == 1 && !Character.isHighSurrogate(seq.charAt(index))) {
3436             assert (index >= 0 && index < seq.length());
3437             return 1;
3438         }
3439         int length = seq.length();
3440         int x = index;
3441         if (lengthInCodePoints >= 0) {
3442             assert (index >= 0 && index < length);
3443             for (int i = 0; x < length && i < lengthInCodePoints; i++) {
3444                 if (Character.isHighSurrogate(seq.charAt(x++))) {
3445                     if (x < length && Character.isLowSurrogate(seq.charAt(x))) {
3446                         x++;
3447                     }
3448                 }
3449             }
3450             return x - index;
3451         }
3452 
3453         assert (index >= 0 && index <= length);
3454         if (index == 0) {
3455             return 0;
3456         }
3457         int len = -lengthInCodePoints;
3458         for (int i = 0; x > 0 && i < len; i++) {
3459             if (Character.isLowSurrogate(seq.charAt(--x))) {
3460                 if (x > 0 && Character.isHighSurrogate(seq.charAt(x-1))) {
3461                     x--;
3462                 }
3463             }
3464         }
3465         return index - x;
3466     }
3467 
3468     private static final int countCodePoints(CharSequence seq) {
3469         int length = seq.length();
3470         int n = 0;
3471         for (int i = 0; i < length; ) {
3472             n++;
3473             if (Character.isHighSurrogate(seq.charAt(i++))) {
3474                 if (i < length && Character.isLowSurrogate(seq.charAt(i))) {
3475                     i++;
3476                 }
3477             }
3478         }
3479         return n;
3480     }
3481 
3482     /**
3483      *  Creates a bit vector for matching Latin-1 values. A normal BitClass
3484      *  never matches values above Latin-1, and a complemented BitClass always
3485      *  matches values above Latin-1.
3486      */
3487     static final class BitClass implements BmpCharPredicate {
3488         final boolean[] bits;
3489         BitClass() {
3490             bits = new boolean[256];
3491         }
3492         BitClass add(int c, int flags) {
3493             assert c >= 0 && c <= 255;
3494             if ((flags & CASE_INSENSITIVE) != 0) {
3495                 if (ASCII.isAscii(c)) {
3496                     bits[ASCII.toUpper(c)] = true;
3497                     bits[ASCII.toLower(c)] = true;
3498                 } else if ((flags & UNICODE_CASE) != 0) {
3499                     bits[Character.toLowerCase(c)] = true;
3500                     bits[Character.toUpperCase(c)] = true;
3501                 }
3502             }
3503             bits[c] = true;
3504             return this;
3505         }
3506         public boolean is(int ch) {
3507             return ch < 256 && bits[ch];
3508         }
3509     }
3510 
3511 
3512     /**
3513      *  Utility method for creating a string slice matcher.
3514      */
3515     private Node newSlice(int[] buf, int count, boolean hasSupplementary) {
3516         int[] tmp = new int[count];
3517         if (has(CASE_INSENSITIVE)) {
3518             if (has(UNICODE_CASE)) {
3519                 for (int i = 0; i < count; i++) {
3520                     tmp[i] = Character.toLowerCase(
3521                                  Character.toUpperCase(buf[i]));
3522                 }
3523                 return hasSupplementary? new SliceUS(tmp) : new SliceU(tmp);
3524             }
3525             for (int i = 0; i < count; i++) {
3526                 tmp[i] = ASCII.toLower(buf[i]);
3527             }
3528             return hasSupplementary? new SliceIS(tmp) : new SliceI(tmp);
3529         }
3530         for (int i = 0; i < count; i++) {
3531             tmp[i] = buf[i];
3532         }
3533         return hasSupplementary ? new SliceS(tmp) : new Slice(tmp);
3534     }
3535 
3536     /**
3537      * The following classes are the building components of the object
3538      * tree that represents a compiled regular expression. The object tree
3539      * is made of individual elements that handle constructs in the Pattern.
3540      * Each type of object knows how to match its equivalent construct with
3541      * the match() method.
3542      */
3543 
3544     /**
3545      * Base class for all node classes. Subclasses should override the match()
3546      * method as appropriate. This class is an accepting node, so its match()
3547      * always returns true.
3548      */
3549     static class Node extends Object {
3550         Node next;
3551         Node() {
3552             next = Pattern.accept;
3553         }
3554         /**
3555          * This method implements the classic accept node.
3556          */
3557         boolean match(Matcher matcher, int i, CharSequence seq) {
3558             matcher.last = i;
3559             matcher.groups[0] = matcher.first;
3560             matcher.groups[1] = matcher.last;
3561             return true;
3562         }
3563         /**
3564          * This method is good for all zero length assertions.
3565          */
3566         boolean study(TreeInfo info) {
3567             if (next != null) {
3568                 return next.study(info);
3569             } else {
3570                 return info.deterministic;
3571             }
3572         }
3573     }
3574 
3575     static class LastNode extends Node {
3576         /**
3577          * This method implements the classic accept node with
3578          * the addition of a check to see if the match occurred
3579          * using all of the input.
3580          */
3581         boolean match(Matcher matcher, int i, CharSequence seq) {
3582             if (matcher.acceptMode == Matcher.ENDANCHOR && i != matcher.to)
3583                 return false;
3584             matcher.last = i;
3585             matcher.groups[0] = matcher.first;
3586             matcher.groups[1] = matcher.last;
3587             return true;
3588         }
3589     }
3590 
3591     /**
3592      * Used for REs that can start anywhere within the input string.
3593      * This basically tries to match repeatedly at each spot in the
3594      * input string, moving forward after each try. An anchored search
3595      * or a BnM will bypass this node completely.
3596      */
3597     static class Start extends Node {
3598         int minLength;
3599         Start(Node node) {
3600             this.next = node;
3601             TreeInfo info = new TreeInfo();
3602             next.study(info);
3603             minLength = info.minLength;
3604         }
3605         boolean match(Matcher matcher, int i, CharSequence seq) {
3606             if (i > matcher.to - minLength) {
3607                 matcher.hitEnd = true;
3608                 return false;
3609             }
3610             int guard = matcher.to - minLength;
3611             for (; i <= guard; i++) {
3612                 if (next.match(matcher, i, seq)) {
3613                     matcher.first = i;
3614                     matcher.groups[0] = matcher.first;
3615                     matcher.groups[1] = matcher.last;
3616                     return true;
3617                 }
3618             }
3619             matcher.hitEnd = true;
3620             return false;
3621         }
3622         boolean study(TreeInfo info) {
3623             next.study(info);
3624             info.maxValid = false;
3625             info.deterministic = false;
3626             return false;
3627         }
3628     }
3629 
3630     /*
3631      * StartS supports supplementary characters, including unpaired surrogates.
3632      */
3633     static final class StartS extends Start {
3634         StartS(Node node) {
3635             super(node);
3636         }
3637         boolean match(Matcher matcher, int i, CharSequence seq) {
3638             if (i > matcher.to - minLength) {
3639                 matcher.hitEnd = true;
3640                 return false;
3641             }
3642             int guard = matcher.to - minLength;
3643             while (i <= guard) {
3644                 //if ((ret = next.match(matcher, i, seq)) || i == guard)
3645                 if (next.match(matcher, i, seq)) {
3646                     matcher.first = i;
3647                     matcher.groups[0] = matcher.first;
3648                     matcher.groups[1] = matcher.last;
3649                     return true;
3650                 }
3651                 if (i == guard)
3652                     break;
3653                 // Optimization to move to the next character. This is
3654                 // faster than countChars(seq, i, 1).
3655                 if (Character.isHighSurrogate(seq.charAt(i++))) {
3656                     if (i < seq.length() &&
3657                         Character.isLowSurrogate(seq.charAt(i))) {
3658                         i++;
3659                     }
3660                 }
3661             }
3662             matcher.hitEnd = true;
3663             return false;
3664         }
3665     }
3666 
3667     /**
3668      * Node to anchor at the beginning of input. This object implements the
3669      * match for a \A sequence, and the caret anchor will use this if not in
3670      * multiline mode.
3671      */
3672     static final class Begin extends Node {
3673         boolean match(Matcher matcher, int i, CharSequence seq) {
3674             int fromIndex = (matcher.anchoringBounds) ?
3675                 matcher.from : 0;
3676             if (i == fromIndex && next.match(matcher, i, seq)) {
3677                 matcher.first = i;
3678                 matcher.groups[0] = i;
3679                 matcher.groups[1] = matcher.last;
3680                 return true;
3681             } else {
3682                 return false;
3683             }
3684         }
3685     }
3686 
3687     /**
3688      * Node to anchor at the end of input. This is the absolute end, so this
3689      * should not match at the last newline before the end as $ will.
3690      */
3691     static final class End extends Node {
3692         boolean match(Matcher matcher, int i, CharSequence seq) {
3693             int endIndex = (matcher.anchoringBounds) ?
3694                 matcher.to : matcher.getTextLength();
3695             if (i == endIndex) {
3696                 matcher.hitEnd = true;
3697                 return next.match(matcher, i, seq);
3698             }
3699             return false;
3700         }
3701     }
3702 
3703     /**
3704      * Node to anchor at the beginning of a line. This is essentially the
3705      * object to match for the multiline ^.
3706      */
3707     static final class Caret extends Node {
3708         boolean match(Matcher matcher, int i, CharSequence seq) {
3709             int startIndex = matcher.from;
3710             int endIndex = matcher.to;
3711             if (!matcher.anchoringBounds) {
3712                 startIndex = 0;
3713                 endIndex = matcher.getTextLength();
3714             }
3715             // Perl does not match ^ at end of input even after newline
3716             if (i == endIndex) {
3717                 matcher.hitEnd = true;
3718                 return false;
3719             }
3720             if (i > startIndex) {
3721                 char ch = seq.charAt(i-1);
3722                 if (ch != '\n' && ch != '\r'
3723                     && (ch|1) != '\u2029'
3724                     && ch != '\u0085' ) {
3725                     return false;
3726                 }
3727                 // Should treat /r/n as one newline
3728                 if (ch == '\r' && seq.charAt(i) == '\n')
3729                     return false;
3730             }
3731             return next.match(matcher, i, seq);
3732         }
3733     }
3734 
3735     /**
3736      * Node to anchor at the beginning of a line when in unixdot mode.
3737      */
3738     static final class UnixCaret extends Node {
3739         boolean match(Matcher matcher, int i, CharSequence seq) {
3740             int startIndex = matcher.from;
3741             int endIndex = matcher.to;
3742             if (!matcher.anchoringBounds) {
3743                 startIndex = 0;
3744                 endIndex = matcher.getTextLength();
3745             }
3746             // Perl does not match ^ at end of input even after newline
3747             if (i == endIndex) {
3748                 matcher.hitEnd = true;
3749                 return false;
3750             }
3751             if (i > startIndex) {
3752                 char ch = seq.charAt(i-1);
3753                 if (ch != '\n') {
3754                     return false;
3755                 }
3756             }
3757             return next.match(matcher, i, seq);
3758         }
3759     }
3760 
3761     /**
3762      * Node to match the location where the last match ended.
3763      * This is used for the \G construct.
3764      */
3765     static final class LastMatch extends Node {
3766         boolean match(Matcher matcher, int i, CharSequence seq) {
3767             if (i != matcher.oldLast)
3768                 return false;
3769             return next.match(matcher, i, seq);
3770         }
3771     }
3772 
3773     /**
3774      * Node to anchor at the end of a line or the end of input based on the
3775      * multiline mode.
3776      *
3777      * When not in multiline mode, the $ can only match at the very end
3778      * of the input, unless the input ends in a line terminator in which
3779      * it matches right before the last line terminator.
3780      *
3781      * Note that \r\n is considered an atomic line terminator.
3782      *
3783      * Like ^ the $ operator matches at a position, it does not match the
3784      * line terminators themselves.
3785      */
3786     static final class Dollar extends Node {
3787         boolean multiline;
3788         Dollar(boolean mul) {
3789             multiline = mul;
3790         }
3791         boolean match(Matcher matcher, int i, CharSequence seq) {
3792             int endIndex = (matcher.anchoringBounds) ?
3793                 matcher.to : matcher.getTextLength();
3794             if (!multiline) {
3795                 if (i < endIndex - 2)
3796                     return false;
3797                 if (i == endIndex - 2) {
3798                     char ch = seq.charAt(i);
3799                     if (ch != '\r')
3800                         return false;
3801                     ch = seq.charAt(i + 1);
3802                     if (ch != '\n')
3803                         return false;
3804                 }
3805             }
3806             // Matches before any line terminator; also matches at the
3807             // end of input
3808             // Before line terminator:
3809             // If multiline, we match here no matter what
3810             // If not multiline, fall through so that the end
3811             // is marked as hit; this must be a /r/n or a /n
3812             // at the very end so the end was hit; more input
3813             // could make this not match here
3814             if (i < endIndex) {
3815                 char ch = seq.charAt(i);
3816                  if (ch == '\n') {
3817                      // No match between \r\n
3818                      if (i > 0 && seq.charAt(i-1) == '\r')
3819                          return false;
3820                      if (multiline)
3821                          return next.match(matcher, i, seq);
3822                  } else if (ch == '\r' || ch == '\u0085' ||
3823                             (ch|1) == '\u2029') {
3824                      if (multiline)
3825                          return next.match(matcher, i, seq);
3826                  } else { // No line terminator, no match
3827                      return false;
3828                  }
3829             }
3830             // Matched at current end so hit end
3831             matcher.hitEnd = true;
3832             // If a $ matches because of end of input, then more input
3833             // could cause it to fail!
3834             matcher.requireEnd = true;
3835             return next.match(matcher, i, seq);
3836         }
3837         boolean study(TreeInfo info) {
3838             next.study(info);
3839             return info.deterministic;
3840         }
3841     }
3842 
3843     /**
3844      * Node to anchor at the end of a line or the end of input based on the
3845      * multiline mode when in unix lines mode.
3846      */
3847     static final class UnixDollar extends Node {
3848         boolean multiline;
3849         UnixDollar(boolean mul) {
3850             multiline = mul;
3851         }
3852         boolean match(Matcher matcher, int i, CharSequence seq) {
3853             int endIndex = (matcher.anchoringBounds) ?
3854                 matcher.to : matcher.getTextLength();
3855             if (i < endIndex) {
3856                 char ch = seq.charAt(i);
3857                 if (ch == '\n') {
3858                     // If not multiline, then only possible to
3859                     // match at very end or one before end
3860                     if (multiline == false && i != endIndex - 1)
3861                         return false;
3862                     // If multiline return next.match without setting
3863                     // matcher.hitEnd
3864                     if (multiline)
3865                         return next.match(matcher, i, seq);
3866                 } else {
3867                     return false;
3868                 }
3869             }
3870             // Matching because at the end or 1 before the end;
3871             // more input could change this so set hitEnd
3872             matcher.hitEnd = true;
3873             // If a $ matches because of end of input, then more input
3874             // could cause it to fail!
3875             matcher.requireEnd = true;
3876             return next.match(matcher, i, seq);
3877         }
3878         boolean study(TreeInfo info) {
3879             next.study(info);
3880             return info.deterministic;
3881         }
3882     }
3883 
3884     /**
3885      * Node class that matches a Unicode line ending '\R'
3886      */
3887     static final class LineEnding extends Node {
3888         boolean match(Matcher matcher, int i, CharSequence seq) {
3889             // (u+000Du+000A|[u+000Au+000Bu+000Cu+000Du+0085u+2028u+2029])
3890             if (i < matcher.to) {
3891                 int ch = seq.charAt(i);
3892                 if (ch == 0x0A || ch == 0x0B || ch == 0x0C ||
3893                     ch == 0x85 || ch == 0x2028 || ch == 0x2029)
3894                     return next.match(matcher, i + 1, seq);
3895                 if (ch == 0x0D) {
3896                     i++;
3897                     if (i < matcher.to) {
3898                         if (seq.charAt(i) == 0x0A &&
3899                             next.match(matcher, i + 1, seq)) {
3900                             return true;
3901                         }
3902                     } else {
3903                         matcher.hitEnd = true;
3904                     }
3905                     return next.match(matcher, i, seq);
3906                 }
3907             } else {
3908                 matcher.hitEnd = true;
3909             }
3910             return false;
3911         }
3912         boolean study(TreeInfo info) {
3913             info.minLength++;
3914             info.maxLength += 2;
3915             return next.study(info);
3916         }
3917     }
3918 
3919     /**
3920      * Abstract node class to match one character satisfying some
3921      * boolean property.
3922      */
3923     static class CharProperty extends Node {
3924         final CharPredicate predicate;
3925 
3926         CharProperty (CharPredicate predicate) {
3927             this.predicate = predicate;
3928         }
3929         boolean match(Matcher matcher, int i, CharSequence seq) {
3930             if (i < matcher.to) {
3931                 int ch = Character.codePointAt(seq, i);
3932                 return predicate.is(ch) &&
3933                        next.match(matcher, i + Character.charCount(ch), seq);
3934             } else {
3935                 matcher.hitEnd = true;
3936                 return false;
3937             }
3938         }
3939         boolean study(TreeInfo info) {
3940             info.minLength++;
3941             info.maxLength++;
3942             return next.study(info);
3943         }
3944     }
3945 
3946     /**
3947      * Optimized version of CharProperty that works only for
3948      * properties never satisfied by Supplementary characters.
3949      */
3950     private static class BmpCharProperty extends CharProperty {
3951         BmpCharProperty (BmpCharPredicate predicate) {
3952             super(predicate);
3953         }
3954         boolean match(Matcher matcher, int i, CharSequence seq) {
3955             if (i < matcher.to) {
3956                 return predicate.is(seq.charAt(i)) &&
3957                        next.match(matcher, i + 1, seq);
3958             } else {
3959                 matcher.hitEnd = true;
3960                 return false;
3961             }
3962         }
3963     }
3964 
3965     private static class NFCCharProperty extends Node {
3966         CharPredicate predicate;
3967         NFCCharProperty (CharPredicate predicate) {
3968             this.predicate = predicate;
3969         }
3970 
3971         boolean match(Matcher matcher, int i, CharSequence seq) {
3972             if (i < matcher.to) {
3973                 int ch0 = Character.codePointAt(seq, i);
3974                 int n = Character.charCount(ch0);
3975                 int j = i + n;
3976                 // Fast check if it's necessary to call Normalizer;
3977                 // testing Grapheme.isBoundary is enough for this case
3978                 while (j < matcher.to) {
3979                     int ch1 = Character.codePointAt(seq, j);
3980                     if (Grapheme.isBoundary(ch0, ch1))
3981                         break;
3982                     ch0 = ch1;
3983                     j += Character.charCount(ch1);
3984                 }
3985                 if (i + n == j) {    // single, assume nfc cp
3986                     if (predicate.is(ch0))
3987                         return next.match(matcher, j, seq);
3988                 } else {
3989                     while (i + n < j) {
3990                         String nfc = Normalizer.normalize(
3991                             seq.toString().substring(i, j), Normalizer.Form.NFC);
3992                         if (nfc.codePointCount(0, nfc.length()) == 1) {
3993                             if (predicate.is(nfc.codePointAt(0)) &&
3994                                 next.match(matcher, j, seq)) {
3995                                 return true;
3996                             }
3997                         }
3998 
3999                         ch0 = Character.codePointBefore(seq, j);
4000                         j -= Character.charCount(ch0);
4001                     }
4002                 }
4003                 if (j < matcher.to)
4004                     return false;
4005             }
4006             matcher.hitEnd = true;
4007             return false;
4008         }
4009 
4010         boolean study(TreeInfo info) {
4011             info.minLength++;
4012             info.deterministic = false;
4013             return next.study(info);
4014         }
4015     }
4016 
4017     /**
4018      * Node class that matches an unicode extended grapheme cluster
4019      */
4020     static class XGrapheme extends Node {
4021         boolean match(Matcher matcher, int i, CharSequence seq) {
4022             if (i < matcher.to) {
4023                 i = Grapheme.nextBoundary(seq, i, matcher.to);
4024                 return next.match(matcher, i, seq);
4025             }
4026             matcher.hitEnd = true;
4027             return false;
4028         }
4029 
4030         boolean study(TreeInfo info) {
4031             info.minLength++;
4032             info.deterministic = false;
4033             return next.study(info);
4034         }
4035     }
4036 
4037     /**
4038      * Node class that handles grapheme boundaries
4039      */
4040     static class GraphemeBound extends Node {
4041         boolean match(Matcher matcher, int i, CharSequence seq) {
4042             int startIndex = matcher.from;
4043             int endIndex = matcher.to;
4044             if (matcher.transparentBounds) {
4045                 startIndex = 0;
4046                 endIndex = matcher.getTextLength();
4047             }
4048             if (i == startIndex) {
4049                 return next.match(matcher, i, seq);
4050             }
4051             if (i < endIndex) {
4052                 if (Character.isSurrogatePair(seq.charAt(i-1), seq.charAt(i)) ||
4053                     Grapheme.nextBoundary(seq,
4054                         i - Character.charCount(Character.codePointBefore(seq, i)),
4055                         i + Character.charCount(Character.codePointAt(seq, i))) > i) {
4056                     return false;
4057                 }
4058             } else {
4059                 matcher.hitEnd = true;
4060                 matcher.requireEnd = true;
4061             }
4062             return next.match(matcher, i, seq);
4063         }
4064     }
4065 
4066     /**
4067      * Base class for all Slice nodes
4068      */
4069     static class SliceNode extends Node {
4070         int[] buffer;
4071         SliceNode(int[] buf) {
4072             buffer = buf;
4073         }
4074         boolean study(TreeInfo info) {
4075             info.minLength += buffer.length;
4076             info.maxLength += buffer.length;
4077             return next.study(info);
4078         }
4079     }
4080 
4081     /**
4082      * Node class for a case sensitive/BMP-only sequence of literal
4083      * characters.
4084      */
4085     static class Slice extends SliceNode {
4086         Slice(int[] buf) {
4087             super(buf);
4088         }
4089         boolean match(Matcher matcher, int i, CharSequence seq) {
4090             int[] buf = buffer;
4091             int len = buf.length;
4092             for (int j=0; j<len; j++) {
4093                 if ((i+j) >= matcher.to) {
4094                     matcher.hitEnd = true;
4095                     return false;
4096                 }
4097                 if (buf[j] != seq.charAt(i+j))
4098                     return false;
4099             }
4100             return next.match(matcher, i+len, seq);
4101         }
4102     }
4103 
4104     /**
4105      * Node class for a case_insensitive/BMP-only sequence of literal
4106      * characters.
4107      */
4108     static class SliceI extends SliceNode {
4109         SliceI(int[] buf) {
4110             super(buf);
4111         }
4112         boolean match(Matcher matcher, int i, CharSequence seq) {
4113             int[] buf = buffer;
4114             int len = buf.length;
4115             for (int j=0; j<len; j++) {
4116                 if ((i+j) >= matcher.to) {
4117                     matcher.hitEnd = true;
4118                     return false;
4119                 }
4120                 int c = seq.charAt(i+j);
4121                 if (buf[j] != c &&
4122                     buf[j] != ASCII.toLower(c))
4123                     return false;
4124             }
4125             return next.match(matcher, i+len, seq);
4126         }
4127     }
4128 
4129     /**
4130      * Node class for a unicode_case_insensitive/BMP-only sequence of
4131      * literal characters. Uses unicode case folding.
4132      */
4133     static final class SliceU extends SliceNode {
4134         SliceU(int[] buf) {
4135             super(buf);
4136         }
4137         boolean match(Matcher matcher, int i, CharSequence seq) {
4138             int[] buf = buffer;
4139             int len = buf.length;
4140             for (int j=0; j<len; j++) {
4141                 if ((i+j) >= matcher.to) {
4142                     matcher.hitEnd = true;
4143                     return false;
4144                 }
4145                 int c = seq.charAt(i+j);
4146                 if (buf[j] != c &&
4147                     buf[j] != Character.toLowerCase(Character.toUpperCase(c)))
4148                     return false;
4149             }
4150             return next.match(matcher, i+len, seq);
4151         }
4152     }
4153 
4154     /**
4155      * Node class for a case sensitive sequence of literal characters
4156      * including supplementary characters.
4157      */
4158     static final class SliceS extends Slice {
4159         SliceS(int[] buf) {
4160             super(buf);
4161         }
4162         boolean match(Matcher matcher, int i, CharSequence seq) {
4163             int[] buf = buffer;
4164             int x = i;
4165             for (int j = 0; j < buf.length; j++) {
4166                 if (x >= matcher.to) {
4167                     matcher.hitEnd = true;
4168                     return false;
4169                 }
4170                 int c = Character.codePointAt(seq, x);
4171                 if (buf[j] != c)
4172                     return false;
4173                 x += Character.charCount(c);
4174                 if (x > matcher.to) {
4175                     matcher.hitEnd = true;
4176                     return false;
4177                 }
4178             }
4179             return next.match(matcher, x, seq);
4180         }
4181     }
4182 
4183     /**
4184      * Node class for a case insensitive sequence of literal characters
4185      * including supplementary characters.
4186      */
4187     static class SliceIS extends SliceNode {
4188         SliceIS(int[] buf) {
4189             super(buf);
4190         }
4191         int toLower(int c) {
4192             return ASCII.toLower(c);
4193         }
4194         boolean match(Matcher matcher, int i, CharSequence seq) {
4195             int[] buf = buffer;
4196             int x = i;
4197             for (int j = 0; j < buf.length; j++) {
4198                 if (x >= matcher.to) {
4199                     matcher.hitEnd = true;
4200                     return false;
4201                 }
4202                 int c = Character.codePointAt(seq, x);
4203                 if (buf[j] != c && buf[j] != toLower(c))
4204                     return false;
4205                 x += Character.charCount(c);
4206                 if (x > matcher.to) {
4207                     matcher.hitEnd = true;
4208                     return false;
4209                 }
4210             }
4211             return next.match(matcher, x, seq);
4212         }
4213     }
4214 
4215     /**
4216      * Node class for a case insensitive sequence of literal characters.
4217      * Uses unicode case folding.
4218      */
4219     static final class SliceUS extends SliceIS {
4220         SliceUS(int[] buf) {
4221             super(buf);
4222         }
4223         int toLower(int c) {
4224             return Character.toLowerCase(Character.toUpperCase(c));
4225         }
4226     }
4227 
4228     /**
4229      * The 0 or 1 quantifier. This one class implements all three types.
4230      */
4231     static final class Ques extends Node {
4232         Node atom;
4233         Qtype type;
4234         Ques(Node node, Qtype type) {
4235             this.atom = node;
4236             this.type = type;
4237         }
4238         boolean match(Matcher matcher, int i, CharSequence seq) {
4239             switch (type) {
4240             case GREEDY:
4241                 return (atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq))
4242                     || next.match(matcher, i, seq);
4243             case LAZY:
4244                 return next.match(matcher, i, seq)
4245                     || (atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq));
4246             case POSSESSIVE:
4247                 if (atom.match(matcher, i, seq)) i = matcher.last;
4248                 return next.match(matcher, i, seq);
4249             default:
4250                 return atom.match(matcher, i, seq) && next.match(matcher, matcher.last, seq);
4251             }
4252         }
4253         boolean study(TreeInfo info) {
4254             if (type != Qtype.INDEPENDENT) {
4255                 int minL = info.minLength;
4256                 atom.study(info);
4257                 info.minLength = minL;
4258                 info.deterministic = false;
4259                 return next.study(info);
4260             } else {
4261                 atom.study(info);
4262                 return next.study(info);
4263             }
4264         }
4265     }
4266 
4267     /**
4268      * Handles the greedy style repetition with the specified minimum
4269      * and the maximum equal to MAX_REPS, for *, + and {N,} quantifiers.
4270      */
4271     static class CharPropertyGreedy extends Node {
4272         final CharPredicate predicate;
4273         final int cmin;
4274 
4275         CharPropertyGreedy(CharProperty cp, int cmin) {
4276             this.predicate = cp.predicate;
4277             this.cmin = cmin;
4278         }
4279         boolean match(Matcher matcher, int i, CharSequence seq) {
4280             int n = 0;
4281             int to = matcher.to;
4282             // greedy, all the way down
4283             while (i < to) {
4284                 int ch = Character.codePointAt(seq, i);
4285                 if (!predicate.is(ch))
4286                    break;
4287                 i += Character.charCount(ch);
4288                 n++;
4289             }
4290             if (i >= to) {
4291                 matcher.hitEnd = true;
4292             }
4293             while (n >= cmin) {
4294                 if (next.match(matcher, i, seq))
4295                     return true;
4296                 if (n == cmin)
4297                     return false;
4298                  // backing off if match fails
4299                 int ch = Character.codePointBefore(seq, i);
4300                 i -= Character.charCount(ch);
4301                 n--;
4302             }
4303             return false;
4304         }
4305 
4306         boolean study(TreeInfo info) {
4307             info.minLength += cmin;
4308             if (info.maxValid) {
4309                 info.maxLength += MAX_REPS;
4310             }
4311             info.deterministic = false;
4312             return next.study(info);
4313         }
4314     }
4315 
4316     static final class BmpCharPropertyGreedy extends CharPropertyGreedy {
4317 
4318         BmpCharPropertyGreedy(BmpCharProperty bcp, int cmin) {
4319             super(bcp, cmin);
4320         }
4321 
4322         boolean match(Matcher matcher, int i, CharSequence seq) {
4323             int n = 0;
4324             int to = matcher.to;
4325             while (i < to && predicate.is(seq.charAt(i))) {
4326                 i++; n++;
4327             }
4328             if (i >= to) {
4329                 matcher.hitEnd = true;
4330             }
4331             while (n >= cmin) {
4332                 if (next.match(matcher, i, seq))
4333                     return true;
4334                 i--; n--;  // backing off if match fails
4335             }
4336             return false;
4337         }
4338     }
4339 
4340     /**
4341      * Handles the curly-brace style repetition with a specified minimum and
4342      * maximum occurrences. The * quantifier is handled as a special case.
4343      * This class handles the three types.
4344      */
4345     static final class Curly extends Node {
4346         Node atom;
4347         Qtype type;
4348         int cmin;
4349         int cmax;
4350 
4351         Curly(Node node, int cmin, int cmax, Qtype type) {
4352             this.atom = node;
4353             this.type = type;
4354             this.cmin = cmin;
4355             this.cmax = cmax;
4356         }
4357         boolean match(Matcher matcher, int i, CharSequence seq) {
4358             int j;
4359             for (j = 0; j < cmin; j++) {
4360                 if (atom.match(matcher, i, seq)) {
4361                     i = matcher.last;
4362                     continue;
4363                 }
4364                 return false;
4365             }
4366             if (type == Qtype.GREEDY)
4367                 return match0(matcher, i, j, seq);
4368             else if (type == Qtype.LAZY)
4369                 return match1(matcher, i, j, seq);
4370             else
4371                 return match2(matcher, i, j, seq);
4372         }
4373         // Greedy match.
4374         // i is the index to start matching at
4375         // j is the number of atoms that have matched
4376         boolean match0(Matcher matcher, int i, int j, CharSequence seq) {
4377             if (j >= cmax) {
4378                 // We have matched the maximum... continue with the rest of
4379                 // the regular expression
4380                 return next.match(matcher, i, seq);
4381             }
4382             int backLimit = j;
4383             while (atom.match(matcher, i, seq)) {
4384                 // k is the length of this match
4385                 int k = matcher.last - i;
4386                 if (k == 0) // Zero length match
4387                     break;
4388                 // Move up index and number matched
4389                 i = matcher.last;
4390                 j++;
4391                 // We are greedy so match as many as we can
4392                 while (j < cmax) {
4393                     if (!atom.match(matcher, i, seq))
4394                         break;
4395                     if (i + k != matcher.last) {
4396                         if (match0(matcher, matcher.last, j+1, seq))
4397                             return true;
4398                         break;
4399                     }
4400                     i += k;
4401                     j++;
4402                 }
4403                 // Handle backing off if match fails
4404                 while (j >= backLimit) {
4405                    if (next.match(matcher, i, seq))
4406                         return true;
4407                     i -= k;
4408                     j--;
4409                 }
4410                 return false;
4411             }
4412             return next.match(matcher, i, seq);
4413         }
4414         // Reluctant match. At this point, the minimum has been satisfied.
4415         // i is the index to start matching at
4416         // j is the number of atoms that have matched
4417         boolean match1(Matcher matcher, int i, int j, CharSequence seq) {
4418             for (;;) {
4419                 // Try finishing match without consuming any more
4420                 if (next.match(matcher, i, seq))
4421                     return true;
4422                 // At the maximum, no match found
4423                 if (j >= cmax)
4424                     return false;
4425                 // Okay, must try one more atom
4426                 if (!atom.match(matcher, i, seq))
4427                     return false;
4428                 // If we haven't moved forward then must break out
4429                 if (i == matcher.last)
4430                     return false;
4431                 // Move up index and number matched
4432                 i = matcher.last;
4433                 j++;
4434             }
4435         }
4436         boolean match2(Matcher matcher, int i, int j, CharSequence seq) {
4437             for (; j < cmax; j++) {
4438                 if (!atom.match(matcher, i, seq))
4439                     break;
4440                 if (i == matcher.last)
4441                     break;
4442                 i = matcher.last;
4443             }
4444             return next.match(matcher, i, seq);
4445         }
4446         boolean study(TreeInfo info) {
4447             // Save original info
4448             int minL = info.minLength;
4449             int maxL = info.maxLength;
4450             boolean maxV = info.maxValid;
4451             boolean detm = info.deterministic;
4452             info.reset();
4453 
4454             atom.study(info);
4455 
4456             int temp = info.minLength * cmin + minL;
4457             if (temp < minL) {
4458                 temp = 0xFFFFFFF; // arbitrary large number
4459             }
4460             info.minLength = temp;
4461 
4462             if (maxV & info.maxValid) {
4463                 temp = info.maxLength * cmax + maxL;
4464                 info.maxLength = temp;
4465                 if (temp < maxL) {
4466                     info.maxValid = false;
4467                 }
4468             } else {
4469                 info.maxValid = false;
4470             }
4471 
4472             if (info.deterministic && cmin == cmax)
4473                 info.deterministic = detm;
4474             else
4475                 info.deterministic = false;
4476             return next.study(info);
4477         }
4478     }
4479 
4480     /**
4481      * Handles the curly-brace style repetition with a specified minimum and
4482      * maximum occurrences in deterministic cases. This is an iterative
4483      * optimization over the Prolog and Loop system which would handle this
4484      * in a recursive way. The * quantifier is handled as a special case.
4485      * If capture is true then this class saves group settings and ensures
4486      * that groups are unset when backing off of a group match.
4487      */
4488     static final class GroupCurly extends Node {
4489         Node atom;
4490         Qtype type;
4491         int cmin;
4492         int cmax;
4493         int localIndex;
4494         int groupIndex;
4495         boolean capture;
4496 
4497         GroupCurly(Node node, int cmin, int cmax, Qtype type, int local,
4498                    int group, boolean capture) {
4499             this.atom = node;
4500             this.type = type;
4501             this.cmin = cmin;
4502             this.cmax = cmax;
4503             this.localIndex = local;
4504             this.groupIndex = group;
4505             this.capture = capture;
4506         }
4507         boolean match(Matcher matcher, int i, CharSequence seq) {
4508             int[] groups = matcher.groups;
4509             int[] locals = matcher.locals;
4510             int save0 = locals[localIndex];
4511             int save1 = 0;
4512             int save2 = 0;
4513 
4514             if (capture) {
4515                 save1 = groups[groupIndex];
4516                 save2 = groups[groupIndex+1];
4517             }
4518 
4519             // Notify GroupTail there is no need to setup group info
4520             // because it will be set here
4521             locals[localIndex] = -1;
4522 
4523             boolean ret = true;
4524             for (int j = 0; j < cmin; j++) {
4525                 if (atom.match(matcher, i, seq)) {
4526                     if (capture) {
4527                         groups[groupIndex] = i;
4528                         groups[groupIndex+1] = matcher.last;
4529                     }
4530                     i = matcher.last;
4531                 } else {
4532                     ret = false;
4533                     break;
4534                 }
4535             }
4536             if (ret) {
4537                 if (type == Qtype.GREEDY) {
4538                     ret = match0(matcher, i, cmin, seq);
4539                 } else if (type == Qtype.LAZY) {
4540                     ret = match1(matcher, i, cmin, seq);
4541                 } else {
4542                     ret = match2(matcher, i, cmin, seq);
4543                 }
4544             }
4545             if (!ret) {
4546                 locals[localIndex] = save0;
4547                 if (capture) {
4548                     groups[groupIndex] = save1;
4549                     groups[groupIndex+1] = save2;
4550                 }
4551             }
4552             return ret;
4553         }
4554         // Aggressive group match
4555         boolean match0(Matcher matcher, int i, int j, CharSequence seq) {
4556             // don't back off passing the starting "j"
4557             int min = j;
4558             int[] groups = matcher.groups;
4559             int save0 = 0;
4560             int save1 = 0;
4561             if (capture) {
4562                 save0 = groups[groupIndex];
4563                 save1 = groups[groupIndex+1];
4564             }
4565             for (;;) {
4566                 if (j >= cmax)
4567                     break;
4568                 if (!atom.match(matcher, i, seq))
4569                     break;
4570                 int k = matcher.last - i;
4571                 if (k <= 0) {
4572                     if (capture) {
4573                         groups[groupIndex] = i;
4574                         groups[groupIndex+1] = i + k;
4575                     }
4576                     i = i + k;
4577                     break;
4578                 }
4579                 for (;;) {
4580                     if (capture) {
4581                         groups[groupIndex] = i;
4582                         groups[groupIndex+1] = i + k;
4583                     }
4584                     i = i + k;
4585                     if (++j >= cmax)
4586                         break;
4587                     if (!atom.match(matcher, i, seq))
4588                         break;
4589                     if (i + k != matcher.last) {
4590                         if (match0(matcher, i, j, seq))
4591                             return true;
4592                         break;
4593                     }
4594                 }
4595                 while (j > min) {
4596                     if (next.match(matcher, i, seq)) {
4597                         if (capture) {
4598                             groups[groupIndex+1] = i;
4599                             groups[groupIndex] = i - k;
4600                         }
4601                         return true;
4602                     }
4603                     // backing off
4604                     i = i - k;
4605                     if (capture) {
4606                         groups[groupIndex+1] = i;
4607                         groups[groupIndex] = i - k;
4608                     }
4609                     j--;
4610 
4611                 }
4612                 break;
4613             }
4614             if (capture) {
4615                 groups[groupIndex] = save0;
4616                 groups[groupIndex+1] = save1;
4617             }
4618             return next.match(matcher, i, seq);
4619         }
4620         // Reluctant matching
4621         boolean match1(Matcher matcher, int i, int j, CharSequence seq) {
4622             for (;;) {
4623                 if (next.match(matcher, i, seq))
4624                     return true;
4625                 if (j >= cmax)
4626                     return false;
4627                 if (!atom.match(matcher, i, seq))
4628                     return false;
4629                 if (i == matcher.last)
4630                     return false;
4631                 if (capture) {
4632                     matcher.groups[groupIndex] = i;
4633                     matcher.groups[groupIndex+1] = matcher.last;
4634                 }
4635                 i = matcher.last;
4636                 j++;
4637             }
4638         }
4639         // Possessive matching
4640         boolean match2(Matcher matcher, int i, int j, CharSequence seq) {
4641             for (; j < cmax; j++) {
4642                 if (!atom.match(matcher, i, seq)) {
4643                     break;
4644                 }
4645                 if (capture) {
4646                     matcher.groups[groupIndex] = i;
4647                     matcher.groups[groupIndex+1] = matcher.last;
4648                 }
4649                 if (i == matcher.last) {
4650                     break;
4651                 }
4652                 i = matcher.last;
4653             }
4654             return next.match(matcher, i, seq);
4655         }
4656         boolean study(TreeInfo info) {
4657             // Save original info
4658             int minL = info.minLength;
4659             int maxL = info.maxLength;
4660             boolean maxV = info.maxValid;
4661             boolean detm = info.deterministic;
4662             info.reset();
4663 
4664             atom.study(info);
4665 
4666             int temp = info.minLength * cmin + minL;
4667             if (temp < minL) {
4668                 temp = 0xFFFFFFF; // Arbitrary large number
4669             }
4670             info.minLength = temp;
4671 
4672             if (maxV & info.maxValid) {
4673                 temp = info.maxLength * cmax + maxL;
4674                 info.maxLength = temp;
4675                 if (temp < maxL) {
4676                     info.maxValid = false;
4677                 }
4678             } else {
4679                 info.maxValid = false;
4680             }
4681 
4682             if (info.deterministic && cmin == cmax) {
4683                 info.deterministic = detm;
4684             } else {
4685                 info.deterministic = false;
4686             }
4687             return next.study(info);
4688         }
4689     }
4690 
4691     /**
4692      * A Guard node at the end of each atom node in a Branch. It
4693      * serves the purpose of chaining the "match" operation to
4694      * "next" but not the "study", so we can collect the TreeInfo
4695      * of each atom node without including the TreeInfo of the
4696      * "next".
4697      */
4698     static final class BranchConn extends Node {
4699         BranchConn() {}
4700         boolean match(Matcher matcher, int i, CharSequence seq) {
4701             return next.match(matcher, i, seq);
4702         }
4703         boolean study(TreeInfo info) {
4704             return info.deterministic;
4705         }
4706     }
4707 
4708     /**
4709      * Handles the branching of alternations. Note this is also used for
4710      * the ? quantifier to branch between the case where it matches once
4711      * and where it does not occur.
4712      */
4713     static final class Branch extends Node {
4714         Node[] atoms = new Node[2];
4715         int size = 2;
4716         Node conn;
4717         Branch(Node first, Node second, Node branchConn) {
4718             conn = branchConn;
4719             atoms[0] = first;
4720             atoms[1] = second;
4721         }
4722 
4723         void add(Node node) {
4724             if (size >= atoms.length) {
4725                 Node[] tmp = new Node[atoms.length*2];
4726                 System.arraycopy(atoms, 0, tmp, 0, atoms.length);
4727                 atoms = tmp;
4728             }
4729             atoms[size++] = node;
4730         }
4731 
4732         boolean match(Matcher matcher, int i, CharSequence seq) {
4733             for (int n = 0; n < size; n++) {
4734                 if (atoms[n] == null) {
4735                     if (conn.next.match(matcher, i, seq))
4736                         return true;
4737                 } else if (atoms[n].match(matcher, i, seq)) {
4738                     return true;
4739                 }
4740             }
4741             return false;
4742         }
4743 
4744         boolean study(TreeInfo info) {
4745             int minL = info.minLength;
4746             int maxL = info.maxLength;
4747             boolean maxV = info.maxValid;
4748 
4749             int minL2 = Integer.MAX_VALUE; //arbitrary large enough num
4750             int maxL2 = -1;
4751             for (int n = 0; n < size; n++) {
4752                 info.reset();
4753                 if (atoms[n] != null)
4754                     atoms[n].study(info);
4755                 minL2 = Math.min(minL2, info.minLength);
4756                 maxL2 = Math.max(maxL2, info.maxLength);
4757                 maxV = (maxV & info.maxValid);
4758             }
4759 
4760             minL += minL2;
4761             maxL += maxL2;
4762 
4763             info.reset();
4764             conn.next.study(info);
4765 
4766             info.minLength += minL;
4767             info.maxLength += maxL;
4768             info.maxValid &= maxV;
4769             info.deterministic = false;
4770             return false;
4771         }
4772     }
4773 
4774     /**
4775      * The GroupHead saves the location where the group begins in the locals
4776      * and restores them when the match is done.
4777      *
4778      * The matchRef is used when a reference to this group is accessed later
4779      * in the expression. The locals will have a negative value in them to
4780      * indicate that we do not want to unset the group if the reference
4781      * doesn't match.
4782      */
4783     static final class GroupHead extends Node {
4784         int localIndex;
4785         GroupTail tail;    // for debug/print only, match does not need to know
4786         GroupHead(int localCount) {
4787             localIndex = localCount;
4788         }
4789         boolean match(Matcher matcher, int i, CharSequence seq) {
4790             int save = matcher.locals[localIndex];
4791             matcher.locals[localIndex] = i;
4792             boolean ret = next.match(matcher, i, seq);
4793             matcher.locals[localIndex] = save;
4794             return ret;
4795         }
4796     }
4797 
4798     /**
4799      * The GroupTail handles the setting of group beginning and ending
4800      * locations when groups are successfully matched. It must also be able to
4801      * unset groups that have to be backed off of.
4802      *
4803      * The GroupTail node is also used when a previous group is referenced,
4804      * and in that case no group information needs to be set.
4805      */
4806     static final class GroupTail extends Node {
4807         int localIndex;
4808         int groupIndex;
4809         GroupTail(int localCount, int groupCount) {
4810             localIndex = localCount;
4811             groupIndex = groupCount + groupCount;
4812         }
4813         boolean match(Matcher matcher, int i, CharSequence seq) {
4814             int tmp = matcher.locals[localIndex];
4815             if (tmp >= 0) { // This is the normal group case.
4816                 // Save the group so we can unset it if it
4817                 // backs off of a match.
4818                 int groupStart = matcher.groups[groupIndex];
4819                 int groupEnd = matcher.groups[groupIndex+1];
4820 
4821                 matcher.groups[groupIndex] = tmp;
4822                 matcher.groups[groupIndex+1] = i;
4823                 if (next.match(matcher, i, seq)) {
4824                     return true;
4825                 }
4826                 matcher.groups[groupIndex] = groupStart;
4827                 matcher.groups[groupIndex+1] = groupEnd;
4828                 return false;
4829             } else {
4830                 // This is a group reference case. We don't need to save any
4831                 // group info because it isn't really a group.
4832                 matcher.last = i;
4833                 return true;
4834             }
4835         }
4836     }
4837 
4838     /**
4839      * This sets up a loop to handle a recursive quantifier structure.
4840      */
4841     static final class Prolog extends Node {
4842         Loop loop;
4843         Prolog(Loop loop) {
4844             this.loop = loop;
4845         }
4846         boolean match(Matcher matcher, int i, CharSequence seq) {
4847             return loop.matchInit(matcher, i, seq);
4848         }
4849         boolean study(TreeInfo info) {
4850             return loop.study(info);
4851         }
4852     }
4853 
4854     /**
4855      * Handles the repetition count for a greedy Curly. The matchInit
4856      * is called from the Prolog to save the index of where the group
4857      * beginning is stored. A zero length group check occurs in the
4858      * normal match but is skipped in the matchInit.
4859      */
4860     static class Loop extends Node {
4861         Node body;
4862         int countIndex; // local count index in matcher locals
4863         int beginIndex; // group beginning index
4864         int cmin, cmax;
4865         int posIndex;
4866         Loop(int countIndex, int beginIndex) {
4867             this.countIndex = countIndex;
4868             this.beginIndex = beginIndex;
4869             this.posIndex = -1;
4870         }
4871         boolean match(Matcher matcher, int i, CharSequence seq) {
4872             // Avoid infinite loop in zero-length case.
4873             if (i > matcher.locals[beginIndex]) {
4874                 int count = matcher.locals[countIndex];
4875 
4876                 // This block is for before we reach the minimum
4877                 // iterations required for the loop to match
4878                 if (count < cmin) {
4879                     matcher.locals[countIndex] = count + 1;
4880                     boolean b = body.match(matcher, i, seq);
4881                     // If match failed we must backtrack, so
4882                     // the loop count should NOT be incremented
4883                     if (!b)
4884                         matcher.locals[countIndex] = count;
4885                     // Return success or failure since we are under
4886                     // minimum
4887                     return b;
4888                 }
4889                 // This block is for after we have the minimum
4890                 // iterations required for the loop to match
4891                 if (count < cmax) {
4892                     // Let's check if we have already tried and failed
4893                     // at this starting position "i" in the past.
4894                     // If yes, then just return false wihtout trying
4895                     // again, to stop the exponential backtracking.
4896                     if (posIndex != -1 &&
4897                         matcher.localsPos[posIndex].contains(i)) {
4898                         return next.match(matcher, i, seq);
4899                     }
4900                     matcher.locals[countIndex] = count + 1;
4901                     boolean b = body.match(matcher, i, seq);
4902                     // If match failed we must backtrack, so
4903                     // the loop count should NOT be incremented
4904                     if (b)
4905                         return true;
4906                     matcher.locals[countIndex] = count;
4907                     // save the failed position
4908                     if (posIndex != -1) {
4909                         matcher.localsPos[posIndex].add(i);
4910                     }
4911                 }
4912             }
4913             return next.match(matcher, i, seq);
4914         }
4915         boolean matchInit(Matcher matcher, int i, CharSequence seq) {
4916             int save = matcher.locals[countIndex];
4917             boolean ret;
4918             if (posIndex != -1 && matcher.localsPos[posIndex] == null) {
4919                 matcher.localsPos[posIndex] = new IntHashSet();
4920             }
4921             if (0 < cmin) {
4922                 matcher.locals[countIndex] = 1;
4923                 ret = body.match(matcher, i, seq);
4924             } else if (0 < cmax) {
4925                 matcher.locals[countIndex] = 1;
4926                 ret = body.match(matcher, i, seq);
4927                 if (ret == false)
4928                     ret = next.match(matcher, i, seq);
4929             } else {
4930                 ret = next.match(matcher, i, seq);
4931             }
4932             matcher.locals[countIndex] = save;
4933             return ret;
4934         }
4935         boolean study(TreeInfo info) {
4936             info.maxValid = false;
4937             info.deterministic = false;
4938             return false;
4939         }
4940     }
4941 
4942     /**
4943      * Handles the repetition count for a reluctant Curly. The matchInit
4944      * is called from the Prolog to save the index of where the group
4945      * beginning is stored. A zero length group check occurs in the
4946      * normal match but is skipped in the matchInit.
4947      */
4948     static final class LazyLoop extends Loop {
4949         LazyLoop(int countIndex, int beginIndex) {
4950             super(countIndex, beginIndex);
4951         }
4952         boolean match(Matcher matcher, int i, CharSequence seq) {
4953             // Check for zero length group
4954             if (i > matcher.locals[beginIndex]) {
4955                 int count = matcher.locals[countIndex];
4956                 if (count < cmin) {
4957                     matcher.locals[countIndex] = count + 1;
4958                     boolean result = body.match(matcher, i, seq);
4959                     // If match failed we must backtrack, so
4960                     // the loop count should NOT be incremented
4961                     if (!result)
4962                         matcher.locals[countIndex] = count;
4963                     return result;
4964                 }
4965                 if (next.match(matcher, i, seq))
4966                     return true;
4967                 if (count < cmax) {
4968                     matcher.locals[countIndex] = count + 1;
4969                     boolean result = body.match(matcher, i, seq);
4970                     // If match failed we must backtrack, so
4971                     // the loop count should NOT be incremented
4972                     if (!result)
4973                         matcher.locals[countIndex] = count;
4974                     return result;
4975                 }
4976                 return false;
4977             }
4978             return next.match(matcher, i, seq);
4979         }
4980         boolean matchInit(Matcher matcher, int i, CharSequence seq) {
4981             int save = matcher.locals[countIndex];
4982             boolean ret = false;
4983             if (0 < cmin) {
4984                 matcher.locals[countIndex] = 1;
4985                 ret = body.match(matcher, i, seq);
4986             } else if (next.match(matcher, i, seq)) {
4987                 ret = true;
4988             } else if (0 < cmax) {
4989                 matcher.locals[countIndex] = 1;
4990                 ret = body.match(matcher, i, seq);
4991             }
4992             matcher.locals[countIndex] = save;
4993             return ret;
4994         }
4995         boolean study(TreeInfo info) {
4996             info.maxValid = false;
4997             info.deterministic = false;
4998             return false;
4999         }
5000     }
5001 
5002     /**
5003      * Refers to a group in the regular expression. Attempts to match
5004      * whatever the group referred to last matched.
5005      */
5006     static class BackRef extends Node {
5007         int groupIndex;
5008         BackRef(int groupCount) {
5009             super();
5010             groupIndex = groupCount + groupCount;
5011         }
5012         boolean match(Matcher matcher, int i, CharSequence seq) {
5013             int j = matcher.groups[groupIndex];
5014             int k = matcher.groups[groupIndex+1];
5015 
5016             int groupSize = k - j;
5017             // If the referenced group didn't match, neither can this
5018             if (j < 0)
5019                 return false;
5020 
5021             // If there isn't enough input left no match
5022             if (i + groupSize > matcher.to) {
5023                 matcher.hitEnd = true;
5024                 return false;
5025             }
5026             // Check each new char to make sure it matches what the group
5027             // referenced matched last time around
5028             for (int index=0; index<groupSize; index++)
5029                 if (seq.charAt(i+index) != seq.charAt(j+index))
5030                     return false;
5031 
5032             return next.match(matcher, i+groupSize, seq);
5033         }
5034         boolean study(TreeInfo info) {
5035             info.maxValid = false;
5036             return next.study(info);
5037         }
5038     }
5039 
5040     static class CIBackRef extends Node {
5041         int groupIndex;
5042         boolean doUnicodeCase;
5043         CIBackRef(int groupCount, boolean doUnicodeCase) {
5044             super();
5045             groupIndex = groupCount + groupCount;
5046             this.doUnicodeCase = doUnicodeCase;
5047         }
5048         boolean match(Matcher matcher, int i, CharSequence seq) {
5049             int j = matcher.groups[groupIndex];
5050             int k = matcher.groups[groupIndex+1];
5051 
5052             int groupSize = k - j;
5053 
5054             // If the referenced group didn't match, neither can this
5055             if (j < 0)
5056                 return false;
5057 
5058             // If there isn't enough input left no match
5059             if (i + groupSize > matcher.to) {
5060                 matcher.hitEnd = true;
5061                 return false;
5062             }
5063 
5064             // Check each new char to make sure it matches what the group
5065             // referenced matched last time around
5066             int x = i;
5067             for (int index=0; index<groupSize; index++) {
5068                 int c1 = Character.codePointAt(seq, x);
5069                 int c2 = Character.codePointAt(seq, j);
5070                 if (c1 != c2) {
5071                     if (doUnicodeCase) {
5072                         int cc1 = Character.toUpperCase(c1);
5073                         int cc2 = Character.toUpperCase(c2);
5074                         if (cc1 != cc2 &&
5075                             Character.toLowerCase(cc1) !=
5076                             Character.toLowerCase(cc2))
5077                             return false;
5078                     } else {
5079                         if (ASCII.toLower(c1) != ASCII.toLower(c2))
5080                             return false;
5081                     }
5082                 }
5083                 x += Character.charCount(c1);
5084                 j += Character.charCount(c2);
5085             }
5086 
5087             return next.match(matcher, i+groupSize, seq);
5088         }
5089         boolean study(TreeInfo info) {
5090             info.maxValid = false;
5091             return next.study(info);
5092         }
5093     }
5094 
5095     /**
5096      * Searches until the next instance of its atom. This is useful for
5097      * finding the atom efficiently without passing an instance of it
5098      * (greedy problem) and without a lot of wasted search time (reluctant
5099      * problem).
5100      */
5101     static final class First extends Node {
5102         Node atom;
5103         First(Node node) {
5104             this.atom = BnM.optimize(node);
5105         }
5106         boolean match(Matcher matcher, int i, CharSequence seq) {
5107             if (atom instanceof BnM) {
5108                 return atom.match(matcher, i, seq)
5109                     && next.match(matcher, matcher.last, seq);
5110             }
5111             for (;;) {
5112                 if (i > matcher.to) {
5113                     matcher.hitEnd = true;
5114                     return false;
5115                 }
5116                 if (atom.match(matcher, i, seq)) {
5117                     return next.match(matcher, matcher.last, seq);
5118                 }
5119                 i += countChars(seq, i, 1);
5120                 matcher.first++;
5121             }
5122         }
5123         boolean study(TreeInfo info) {
5124             atom.study(info);
5125             info.maxValid = false;
5126             info.deterministic = false;
5127             return next.study(info);
5128         }
5129     }
5130 
5131     /**
5132      * Zero width positive lookahead.
5133      */
5134     static final class Pos extends Node {
5135         Node cond;
5136         Pos(Node cond) {
5137             this.cond = cond;
5138         }
5139         boolean match(Matcher matcher, int i, CharSequence seq) {
5140             int savedTo = matcher.to;
5141             boolean conditionMatched;
5142 
5143             // Relax transparent region boundaries for lookahead
5144             if (matcher.transparentBounds)
5145                 matcher.to = matcher.getTextLength();
5146             try {
5147                 conditionMatched = cond.match(matcher, i, seq);
5148             } finally {
5149                 // Reinstate region boundaries
5150                 matcher.to = savedTo;
5151             }
5152             return conditionMatched && next.match(matcher, i, seq);
5153         }
5154     }
5155 
5156     /**
5157      * Zero width negative lookahead.
5158      */
5159     static final class Neg extends Node {
5160         Node cond;
5161         Neg(Node cond) {
5162             this.cond = cond;
5163         }
5164         boolean match(Matcher matcher, int i, CharSequence seq) {
5165             int savedTo = matcher.to;
5166             boolean conditionMatched;
5167 
5168             // Relax transparent region boundaries for lookahead
5169             if (matcher.transparentBounds)
5170                 matcher.to = matcher.getTextLength();
5171             try {
5172                 if (i < matcher.to) {
5173                     conditionMatched = !cond.match(matcher, i, seq);
5174                 } else {
5175                     // If a negative lookahead succeeds then more input
5176                     // could cause it to fail!
5177                     matcher.requireEnd = true;
5178                     conditionMatched = !cond.match(matcher, i, seq);
5179                 }
5180             } finally {
5181                 // Reinstate region boundaries
5182                 matcher.to = savedTo;
5183             }
5184             return conditionMatched && next.match(matcher, i, seq);
5185         }
5186     }
5187 
5188     /**
5189      * For use with lookbehinds; matches the position where the lookbehind
5190      * was encountered.
5191      */
5192     static class LookBehindEndNode extends Node {
5193         private LookBehindEndNode() {} // Singleton
5194 
5195         static LookBehindEndNode INSTANCE = new LookBehindEndNode();
5196 
5197         boolean match(Matcher matcher, int i, CharSequence seq) {
5198             return i == matcher.lookbehindTo;
5199         }
5200     }
5201 
5202     /**
5203      * Zero width positive lookbehind.
5204      */
5205     static class Behind extends Node {
5206         Node cond;
5207         int rmax, rmin;
5208         Behind(Node cond, int rmax, int rmin) {
5209             this.cond = cond;
5210             this.rmax = rmax;
5211             this.rmin = rmin;
5212         }
5213 
5214         boolean match(Matcher matcher, int i, CharSequence seq) {
5215             int savedFrom = matcher.from;
5216             boolean conditionMatched = false;
5217             int startIndex = (!matcher.transparentBounds) ?
5218                              matcher.from : 0;
5219             int from = Math.max(i - rmax, startIndex);
5220             // Set end boundary
5221             int savedLBT = matcher.lookbehindTo;
5222             matcher.lookbehindTo = i;
5223             // Relax transparent region boundaries for lookbehind
5224             if (matcher.transparentBounds)
5225                 matcher.from = 0;
5226             for (int j = i - rmin; !conditionMatched && j >= from; j--) {
5227                 conditionMatched = cond.match(matcher, j, seq);
5228             }
5229             matcher.from = savedFrom;
5230             matcher.lookbehindTo = savedLBT;
5231             return conditionMatched && next.match(matcher, i, seq);
5232         }
5233     }
5234 
5235     /**
5236      * Zero width positive lookbehind, including supplementary
5237      * characters or unpaired surrogates.
5238      */
5239     static final class BehindS extends Behind {
5240         BehindS(Node cond, int rmax, int rmin) {
5241             super(cond, rmax, rmin);
5242         }
5243         boolean match(Matcher matcher, int i, CharSequence seq) {
5244             int rmaxChars = countChars(seq, i, -rmax);
5245             int rminChars = countChars(seq, i, -rmin);
5246             int savedFrom = matcher.from;
5247             int startIndex = (!matcher.transparentBounds) ?
5248                              matcher.from : 0;
5249             boolean conditionMatched = false;
5250             int from = Math.max(i - rmaxChars, startIndex);
5251             // Set end boundary
5252             int savedLBT = matcher.lookbehindTo;
5253             matcher.lookbehindTo = i;
5254             // Relax transparent region boundaries for lookbehind
5255             if (matcher.transparentBounds)
5256                 matcher.from = 0;
5257 
5258             for (int j = i - rminChars;
5259                  !conditionMatched && j >= from;
5260                  j -= j>from ? countChars(seq, j, -1) : 1) {
5261                 conditionMatched = cond.match(matcher, j, seq);
5262             }
5263             matcher.from = savedFrom;
5264             matcher.lookbehindTo = savedLBT;
5265             return conditionMatched && next.match(matcher, i, seq);
5266         }
5267     }
5268 
5269     /**
5270      * Zero width negative lookbehind.
5271      */
5272     static class NotBehind extends Node {
5273         Node cond;
5274         int rmax, rmin;
5275         NotBehind(Node cond, int rmax, int rmin) {
5276             this.cond = cond;
5277             this.rmax = rmax;
5278             this.rmin = rmin;
5279         }
5280 
5281         boolean match(Matcher matcher, int i, CharSequence seq) {
5282             int savedLBT = matcher.lookbehindTo;
5283             int savedFrom = matcher.from;
5284             boolean conditionMatched = false;
5285             int startIndex = (!matcher.transparentBounds) ?
5286                              matcher.from : 0;
5287             int from = Math.max(i - rmax, startIndex);
5288             matcher.lookbehindTo = i;
5289             // Relax transparent region boundaries for lookbehind
5290             if (matcher.transparentBounds)
5291                 matcher.from = 0;
5292             for (int j = i - rmin; !conditionMatched && j >= from; j--) {
5293                 conditionMatched = cond.match(matcher, j, seq);
5294             }
5295             // Reinstate region boundaries
5296             matcher.from = savedFrom;
5297             matcher.lookbehindTo = savedLBT;
5298             return !conditionMatched && next.match(matcher, i, seq);
5299         }
5300     }
5301 
5302     /**
5303      * Zero width negative lookbehind, including supplementary
5304      * characters or unpaired surrogates.
5305      */
5306     static final class NotBehindS extends NotBehind {
5307         NotBehindS(Node cond, int rmax, int rmin) {
5308             super(cond, rmax, rmin);
5309         }
5310         boolean match(Matcher matcher, int i, CharSequence seq) {
5311             int rmaxChars = countChars(seq, i, -rmax);
5312             int rminChars = countChars(seq, i, -rmin);
5313             int savedFrom = matcher.from;
5314             int savedLBT = matcher.lookbehindTo;
5315             boolean conditionMatched = false;
5316             int startIndex = (!matcher.transparentBounds) ?
5317                              matcher.from : 0;
5318             int from = Math.max(i - rmaxChars, startIndex);
5319             matcher.lookbehindTo = i;
5320             // Relax transparent region boundaries for lookbehind
5321             if (matcher.transparentBounds)
5322                 matcher.from = 0;
5323             for (int j = i - rminChars;
5324                  !conditionMatched && j >= from;
5325                  j -= j>from ? countChars(seq, j, -1) : 1) {
5326                 conditionMatched = cond.match(matcher, j, seq);
5327             }
5328             //Reinstate region boundaries
5329             matcher.from = savedFrom;
5330             matcher.lookbehindTo = savedLBT;
5331             return !conditionMatched && next.match(matcher, i, seq);
5332         }
5333     }
5334 
5335     /**
5336      * Handles word boundaries. Includes a field to allow this one class to
5337      * deal with the different types of word boundaries we can match. The word
5338      * characters include underscores, letters, and digits. Non spacing marks
5339      * can are also part of a word if they have a base character, otherwise
5340      * they are ignored for purposes of finding word boundaries.
5341      */
5342     static final class Bound extends Node {
5343         static int LEFT = 0x1;
5344         static int RIGHT= 0x2;
5345         static int BOTH = 0x3;
5346         static int NONE = 0x4;
5347         int type;
5348         boolean useUWORD;
5349         Bound(int n, boolean useUWORD) {
5350             type = n;
5351             this.useUWORD = useUWORD;
5352         }
5353 
5354         boolean isWord(int ch) {
5355             return useUWORD ? CharPredicates.WORD().is(ch)
5356                             : (ch == '_' || Character.isLetterOrDigit(ch));
5357         }
5358 
5359         int check(Matcher matcher, int i, CharSequence seq) {
5360             int ch;
5361             boolean left = false;
5362             int startIndex = matcher.from;
5363             int endIndex = matcher.to;
5364             if (matcher.transparentBounds) {
5365                 startIndex = 0;
5366                 endIndex = matcher.getTextLength();
5367             }
5368             if (i > startIndex) {
5369                 ch = Character.codePointBefore(seq, i);
5370                 left = (isWord(ch) ||
5371                     ((Character.getType(ch) == Character.NON_SPACING_MARK)
5372                      && hasBaseCharacter(matcher, i-1, seq)));
5373             }
5374             boolean right = false;
5375             if (i < endIndex) {
5376                 ch = Character.codePointAt(seq, i);
5377                 right = (isWord(ch) ||
5378                     ((Character.getType(ch) == Character.NON_SPACING_MARK)
5379                      && hasBaseCharacter(matcher, i, seq)));
5380             } else {
5381                 // Tried to access char past the end
5382                 matcher.hitEnd = true;
5383                 // The addition of another char could wreck a boundary
5384                 matcher.requireEnd = true;
5385             }
5386             return ((left ^ right) ? (right ? LEFT : RIGHT) : NONE);
5387         }
5388         boolean match(Matcher matcher, int i, CharSequence seq) {
5389             return (check(matcher, i, seq) & type) > 0
5390                 && next.match(matcher, i, seq);
5391         }
5392     }
5393 
5394     /**
5395      * Non spacing marks only count as word characters in bounds calculations
5396      * if they have a base character.
5397      */
5398     private static boolean hasBaseCharacter(Matcher matcher, int i,
5399                                             CharSequence seq)
5400     {
5401         int start = (!matcher.transparentBounds) ?
5402             matcher.from : 0;
5403         for (int x=i; x >= start; x--) {
5404             int ch = Character.codePointAt(seq, x);
5405             if (Character.isLetterOrDigit(ch))
5406                 return true;
5407             if (Character.getType(ch) == Character.NON_SPACING_MARK)
5408                 continue;
5409             return false;
5410         }
5411         return false;
5412     }
5413 
5414     /**
5415      * Attempts to match a slice in the input using the Boyer-Moore string
5416      * matching algorithm. The algorithm is based on the idea that the
5417      * pattern can be shifted farther ahead in the search text if it is
5418      * matched right to left.
5419      * <p>
5420      * The pattern is compared to the input one character at a time, from
5421      * the rightmost character in the pattern to the left. If the characters
5422      * all match the pattern has been found. If a character does not match,
5423      * the pattern is shifted right a distance that is the maximum of two
5424      * functions, the bad character shift and the good suffix shift. This
5425      * shift moves the attempted match position through the input more
5426      * quickly than a naive one position at a time check.
5427      * <p>
5428      * The bad character shift is based on the character from the text that
5429      * did not match. If the character does not appear in the pattern, the
5430      * pattern can be shifted completely beyond the bad character. If the
5431      * character does occur in the pattern, the pattern can be shifted to
5432      * line the pattern up with the next occurrence of that character.
5433      * <p>
5434      * The good suffix shift is based on the idea that some subset on the right
5435      * side of the pattern has matched. When a bad character is found, the
5436      * pattern can be shifted right by the pattern length if the subset does
5437      * not occur again in pattern, or by the amount of distance to the
5438      * next occurrence of the subset in the pattern.
5439      *
5440      * Boyer-Moore search methods adapted from code by Amy Yu.
5441      */
5442     static class BnM extends Node {
5443         int[] buffer;
5444         int[] lastOcc;
5445         int[] optoSft;
5446 
5447         /**
5448          * Pre calculates arrays needed to generate the bad character
5449          * shift and the good suffix shift. Only the last seven bits
5450          * are used to see if chars match; This keeps the tables small
5451          * and covers the heavily used ASCII range, but occasionally
5452          * results in an aliased match for the bad character shift.
5453          */
5454         static Node optimize(Node node) {
5455             if (!(node instanceof Slice)) {
5456                 return node;
5457             }
5458 
5459             int[] src = ((Slice) node).buffer;
5460             int patternLength = src.length;
5461             // The BM algorithm requires a bit of overhead;
5462             // If the pattern is short don't use it, since
5463             // a shift larger than the pattern length cannot
5464             // be used anyway.
5465             if (patternLength < 4) {
5466                 return node;
5467             }
5468             int i, j;
5469             int[] lastOcc = new int[128];
5470             int[] optoSft = new int[patternLength];
5471             // Precalculate part of the bad character shift
5472             // It is a table for where in the pattern each
5473             // lower 7-bit value occurs
5474             for (i = 0; i < patternLength; i++) {
5475                 lastOcc[src[i]&0x7F] = i + 1;
5476             }
5477             // Precalculate the good suffix shift
5478             // i is the shift amount being considered
5479 NEXT:       for (i = patternLength; i > 0; i--) {
5480                 // j is the beginning index of suffix being considered
5481                 for (j = patternLength - 1; j >= i; j--) {
5482                     // Testing for good suffix
5483                     if (src[j] == src[j-i]) {
5484                         // src[j..len] is a good suffix
5485                         optoSft[j-1] = i;
5486                     } else {
5487                         // No match. The array has already been
5488                         // filled up with correct values before.
5489                         continue NEXT;
5490                     }
5491                 }
5492                 // This fills up the remaining of optoSft
5493                 // any suffix can not have larger shift amount
5494                 // then its sub-suffix. Why???
5495                 while (j > 0) {
5496                     optoSft[--j] = i;
5497                 }
5498             }
5499             // Set the guard value because of unicode compression
5500             optoSft[patternLength-1] = 1;
5501             if (node instanceof SliceS)
5502                 return new BnMS(src, lastOcc, optoSft, node.next);
5503             return new BnM(src, lastOcc, optoSft, node.next);
5504         }
5505         BnM(int[] src, int[] lastOcc, int[] optoSft, Node next) {
5506             this.buffer = src;
5507             this.lastOcc = lastOcc;
5508             this.optoSft = optoSft;
5509             this.next = next;
5510         }
5511         boolean match(Matcher matcher, int i, CharSequence seq) {
5512             int[] src = buffer;
5513             int patternLength = src.length;
5514             int last = matcher.to - patternLength;
5515 
5516             // Loop over all possible match positions in text
5517 NEXT:       while (i <= last) {
5518                 // Loop over pattern from right to left
5519                 for (int j = patternLength - 1; j >= 0; j--) {
5520                     int ch = seq.charAt(i+j);
5521                     if (ch != src[j]) {
5522                         // Shift search to the right by the maximum of the
5523                         // bad character shift and the good suffix shift
5524                         i += Math.max(j + 1 - lastOcc[ch&0x7F], optoSft[j]);
5525                         continue NEXT;
5526                     }
5527                 }
5528                 // Entire pattern matched starting at i
5529                 matcher.first = i;
5530                 boolean ret = next.match(matcher, i + patternLength, seq);
5531                 if (ret) {
5532                     matcher.first = i;
5533                     matcher.groups[0] = matcher.first;
5534                     matcher.groups[1] = matcher.last;
5535                     return true;
5536                 }
5537                 i++;
5538             }
5539             // BnM is only used as the leading node in the unanchored case,
5540             // and it replaced its Start() which always searches to the end
5541             // if it doesn't find what it's looking for, so hitEnd is true.
5542             matcher.hitEnd = true;
5543             return false;
5544         }
5545         boolean study(TreeInfo info) {
5546             info.minLength += buffer.length;
5547             info.maxValid = false;
5548             return next.study(info);
5549         }
5550     }
5551 
5552     /**
5553      * Supplementary support version of BnM(). Unpaired surrogates are
5554      * also handled by this class.
5555      */
5556     static final class BnMS extends BnM {
5557         int lengthInChars;
5558 
5559         BnMS(int[] src, int[] lastOcc, int[] optoSft, Node next) {
5560             super(src, lastOcc, optoSft, next);
5561             for (int cp : buffer) {
5562                 lengthInChars += Character.charCount(cp);
5563             }
5564         }
5565         boolean match(Matcher matcher, int i, CharSequence seq) {
5566             int[] src = buffer;
5567             int patternLength = src.length;
5568             int last = matcher.to - lengthInChars;
5569 
5570             // Loop over all possible match positions in text
5571 NEXT:       while (i <= last) {
5572                 // Loop over pattern from right to left
5573                 int ch;
5574                 for (int j = countChars(seq, i, patternLength), x = patternLength - 1;
5575                      j > 0; j -= Character.charCount(ch), x--) {
5576                     ch = Character.codePointBefore(seq, i+j);
5577                     if (ch != src[x]) {
5578                         // Shift search to the right by the maximum of the
5579                         // bad character shift and the good suffix shift
5580                         int n = Math.max(x + 1 - lastOcc[ch&0x7F], optoSft[x]);
5581                         i += countChars(seq, i, n);
5582                         continue NEXT;
5583                     }
5584                 }
5585                 // Entire pattern matched starting at i
5586                 matcher.first = i;
5587                 boolean ret = next.match(matcher, i + lengthInChars, seq);
5588                 if (ret) {
5589                     matcher.first = i;
5590                     matcher.groups[0] = matcher.first;
5591                     matcher.groups[1] = matcher.last;
5592                     return true;
5593                 }
5594                 i += countChars(seq, i, 1);
5595             }
5596             matcher.hitEnd = true;
5597             return false;
5598         }
5599     }
5600 
5601     @FunctionalInterface
5602     static interface CharPredicate {
5603         boolean is(int ch);
5604 
5605         default CharPredicate and(CharPredicate p) {
5606             return ch -> is(ch) && p.is(ch);
5607         }
5608         default CharPredicate union(CharPredicate p) {
5609             return ch -> is(ch) || p.is(ch);
5610         }
5611         default CharPredicate union(CharPredicate p1,
5612                                     CharPredicate p2 ) {
5613             return ch -> is(ch) || p1.is(ch) || p2.is(ch);
5614         }
5615         default CharPredicate negate() {
5616             return ch -> !is(ch);
5617         }
5618     }
5619 
5620     static interface BmpCharPredicate extends CharPredicate {
5621 
5622         default CharPredicate and(CharPredicate p) {
5623             if (p instanceof BmpCharPredicate)
5624                 return (BmpCharPredicate)(ch -> is(ch) && p.is(ch));
5625             return ch -> is(ch) && p.is(ch);
5626         }
5627         default CharPredicate union(CharPredicate p) {
5628             if (p instanceof BmpCharPredicate)
5629                 return (BmpCharPredicate)(ch -> is(ch) || p.is(ch));
5630             return ch -> is(ch) || p.is(ch);
5631         }
5632         static CharPredicate union(CharPredicate... predicates) {
5633             CharPredicate cp = ch -> {
5634                 for (CharPredicate p : predicates) {
5635                     if (!p.is(ch))
5636                         return false;
5637                 }
5638                 return true;
5639             };
5640             for (CharPredicate p : predicates) {
5641                 if (! (p instanceof BmpCharPredicate))
5642                     return cp;
5643             }
5644             return (BmpCharPredicate)cp;
5645         }
5646     }
5647 
5648     /**
5649      * matches a Perl vertical whitespace
5650      */
5651     static BmpCharPredicate VertWS() {
5652         return cp -> (cp >= 0x0A && cp <= 0x0D) ||
5653             cp == 0x85 || cp == 0x2028 || cp == 0x2029;
5654     }
5655 
5656     /**
5657      * matches a Perl horizontal whitespace
5658      */
5659     static BmpCharPredicate HorizWS() {
5660         return cp ->
5661             cp == 0x09 || cp == 0x20 || cp == 0xa0 || cp == 0x1680 ||
5662             cp == 0x180e || cp >= 0x2000 && cp <= 0x200a ||  cp == 0x202f ||
5663             cp == 0x205f || cp == 0x3000;
5664     }
5665 
5666     /**
5667      *  for the Unicode category ALL and the dot metacharacter when
5668      *  in dotall mode.
5669      */
5670     static CharPredicate ALL() {
5671         return ch -> true;
5672     }
5673 
5674     /**
5675      * for the dot metacharacter when dotall is not enabled.
5676      */
5677     static CharPredicate DOT() {
5678         return ch ->
5679             (ch != '\n' && ch != '\r'
5680             && (ch|1) != '\u2029'
5681             && ch != '\u0085');
5682     }
5683 
5684     /**
5685      *  the dot metacharacter when dotall is not enabled but UNIX_LINES is enabled.
5686      */
5687     static CharPredicate UNIXDOT() {
5688         return ch ->  ch != '\n';
5689     }
5690 
5691     /**
5692      * Indicate that matches a Supplementary Unicode character
5693      */
5694     static CharPredicate SingleS(int c) {
5695         return ch -> ch == c;
5696     }
5697 
5698     /**
5699      * A bmp/optimized predicate of single
5700      */
5701     static BmpCharPredicate Single(int c) {
5702         return ch -> ch == c;
5703     }
5704 
5705     /**
5706      * Case insensitive matches a given BMP character
5707      */
5708     static BmpCharPredicate SingleI(int lower, int upper) {
5709         return ch -> ch == lower || ch == upper;
5710     }
5711 
5712     /**
5713      * Unicode case insensitive matches a given Unicode character
5714      */
5715     static CharPredicate SingleU(int lower) {
5716         return ch -> lower == ch ||
5717                      lower == Character.toLowerCase(Character.toUpperCase(ch));
5718     }
5719 
5720     private static boolean inRange(int lower, int ch, int upper) {
5721         return lower <= ch && ch <= upper;
5722     }
5723 
5724     /**
5725      * Charactrs within a explicit value range
5726      */
5727     static CharPredicate Range(int lower, int upper) {
5728         if (upper < Character.MIN_HIGH_SURROGATE ||
5729             lower > Character.MAX_HIGH_SURROGATE &&
5730             upper < Character.MIN_SUPPLEMENTARY_CODE_POINT)
5731             return (BmpCharPredicate)(ch -> inRange(lower, ch, upper));
5732         return ch -> inRange(lower, ch, upper);
5733     }
5734 
5735    /**
5736     * Charactrs within a explicit value range in a case insensitive manner.
5737     */
5738     static CharPredicate CIRange(int lower, int upper) {
5739         return ch -> inRange(lower, ch, upper) ||
5740                      ASCII.isAscii(ch) &&
5741                      (inRange(lower, ASCII.toUpper(ch), upper) ||
5742                       inRange(lower, ASCII.toLower(ch), upper));
5743     }
5744 
5745     static CharPredicate CIRangeU(int lower, int upper) {
5746         return ch -> {
5747             if (inRange(lower, ch, upper))
5748                 return true;
5749             int up = Character.toUpperCase(ch);
5750             return inRange(lower, up, upper) ||
5751                    inRange(lower, Character.toLowerCase(up), upper);
5752         };
5753     }
5754 
5755     /**
5756      *  This must be the very first initializer.
5757      */
5758     static final Node accept = new Node();
5759 
5760     static final Node lastAccept = new LastNode();
5761 
5762     /**
5763      * Creates a predicate that tests if this pattern is found in a given input
5764      * string.
5765      *
5766      * @apiNote
5767      * This method creates a predicate that behaves as if it creates a matcher
5768      * from the input sequence and then calls {@code find}, for example a
5769      * predicate of the form:
5770      * <pre>{@code
5771      *   s -> matcher(s).find();
5772      * }</pre>
5773      *
5774      * @return  The predicate which can be used for finding a match on a
5775      *          subsequence of a string
5776      * @since   1.8
5777      * @see     Matcher#find
5778      */
5779     public Predicate<String> asPredicate() {
5780         return s -> matcher(s).find();
5781     }
5782 
5783     /**
5784      * Creates a predicate that tests if this pattern matches a given input string.
5785      *
5786      * @apiNote
5787      * This method creates a predicate that behaves as if it creates a matcher
5788      * from the input sequence and then calls {@code matches}, for example a
5789      * predicate of the form:
5790      * <pre>{@code
5791      *   s -> matcher(s).matches();
5792      * }</pre>
5793      *
5794      * @return  The predicate which can be used for matching an input string
5795      *          against this pattern.
5796      * @since   11
5797      * @see     Matcher#matches
5798      */
5799     public Predicate<String> asMatchPredicate() {
5800         return s -> matcher(s).matches();
5801     }
5802 
5803     /**
5804      * Creates a stream from the given input sequence around matches of this
5805      * pattern.
5806      *
5807      * <p> The stream returned by this method contains each substring of the
5808      * input sequence that is terminated by another subsequence that matches
5809      * this pattern or is terminated by the end of the input sequence.  The
5810      * substrings in the stream are in the order in which they occur in the
5811      * input. Trailing empty strings will be discarded and not encountered in
5812      * the stream.
5813      *
5814      * <p> If this pattern does not match any subsequence of the input then
5815      * the resulting stream has just one element, namely the input sequence in
5816      * string form.
5817      *
5818      * <p> When there is a positive-width match at the beginning of the input
5819      * sequence then an empty leading substring is included at the beginning
5820      * of the stream. A zero-width match at the beginning however never produces
5821      * such empty leading substring.
5822      *
5823      * <p> If the input sequence is mutable, it must remain constant during the
5824      * execution of the terminal stream operation.  Otherwise, the result of the
5825      * terminal stream operation is undefined.
5826      *
5827      * @param   input
5828      *          The character sequence to be split
5829      *
5830      * @return  The stream of strings computed by splitting the input
5831      *          around matches of this pattern
5832      * @see     #split(CharSequence)
5833      * @since   1.8
5834      */
5835     public Stream<String> splitAsStream(final CharSequence input) {
5836         class MatcherIterator implements Iterator<String> {
5837             private Matcher matcher;
5838             // The start position of the next sub-sequence of input
5839             // when current == input.length there are no more elements
5840             private int current;
5841             // null if the next element, if any, needs to obtained
5842             private String nextElement;
5843             // > 0 if there are N next empty elements
5844             private int emptyElementCount;
5845 
5846             public String next() {
5847                 if (!hasNext())
5848                     throw new NoSuchElementException();
5849 
5850                 if (emptyElementCount == 0) {
5851                     String n = nextElement;
5852                     nextElement = null;
5853                     return n;
5854                 } else {
5855                     emptyElementCount--;
5856                     return "";
5857                 }
5858             }
5859 
5860             public boolean hasNext() {
5861                 if (matcher == null) {
5862                     matcher = matcher(input);
5863                     // If the input is an empty string then the result can only be a
5864                     // stream of the input.  Induce that by setting the empty
5865                     // element count to 1
5866                     emptyElementCount = input.length() == 0 ? 1 : 0;
5867                 }
5868                 if (nextElement != null || emptyElementCount > 0)
5869                     return true;
5870 
5871                 if (current == input.length())
5872                     return false;
5873 
5874                 // Consume the next matching element
5875                 // Count sequence of matching empty elements
5876                 while (matcher.find()) {
5877                     nextElement = input.subSequence(current, matcher.start()).toString();
5878                     current = matcher.end();
5879                     if (!nextElement.isEmpty()) {
5880                         return true;
5881                     } else if (current > 0) { // no empty leading substring for zero-width
5882                                               // match at the beginning of the input
5883                         emptyElementCount++;
5884                     }
5885                 }
5886 
5887                 // Consume last matching element
5888                 nextElement = input.subSequence(current, input.length()).toString();
5889                 current = input.length();
5890                 if (!nextElement.isEmpty()) {
5891                     return true;
5892                 } else {
5893                     // Ignore a terminal sequence of matching empty elements
5894                     emptyElementCount = 0;
5895                     nextElement = null;
5896                     return false;
5897                 }
5898             }
5899         }
5900         return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
5901                 new MatcherIterator(), Spliterator.ORDERED | Spliterator.NONNULL), false);
5902     }
5903 }