1 /*
2 * Copyright (c) 1994, 2024, 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.lang;
27
28 import jdk.internal.misc.CDS;
29 import jdk.internal.misc.VM;
30 import jdk.internal.util.DecimalDigits;
31 import jdk.internal.value.DeserializeConstructor;
32 import jdk.internal.vm.annotation.ForceInline;
33 import jdk.internal.vm.annotation.IntrinsicCandidate;
34 import jdk.internal.vm.annotation.Stable;
35
36 import java.lang.annotation.Native;
37 import java.lang.constant.Constable;
38 import java.lang.constant.ConstantDesc;
39 import java.lang.invoke.MethodHandles;
40 import java.util.Objects;
41 import java.util.Optional;
42
43 import static java.lang.Character.digit;
44 import static java.lang.String.COMPACT_STRINGS;
45 import static java.lang.String.LATIN1;
46 import static java.lang.String.UTF16;
47
48 /**
49 * The {@code Integer} class is the {@linkplain
50 * java.lang##wrapperClass wrapper class} for values of the primitive
51 * type {@code int}. An object of type {@code Integer} contains a
52 * single field whose type is {@code int}.
53 *
54 * <p>In addition, this class provides several methods for converting
55 * an {@code int} to a {@code String} and a {@code String} to an
56 * {@code int}, as well as other constants and methods useful when
57 * dealing with an {@code int}.
58 *
59 * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
60 * class; programmers should treat instances that are
61 * {@linkplain #equals(Object) equal} as interchangeable and should not
62 * use instances for synchronization, or unpredictable behavior may
63 * occur. For example, in a future release, synchronization may fail.
64 *
65 * <p>Implementation note: The implementations of the "bit twiddling"
66 * methods (such as {@link #highestOneBit(int) highestOneBit} and
67 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
68 * based on material from Henry S. Warren, Jr.'s <cite>Hacker's
69 * Delight</cite>, (Addison Wesley, 2002) and <cite>Hacker's
70 * Delight, Second Edition</cite>, (Pearson Education, 2013).
71 *
72 * @author Lee Boynton
73 * @author Arthur van Hoff
74 * @author Josh Bloch
75 * @author Joseph D. Darcy
76 * @since 1.0
77 */
78 @jdk.internal.MigratedValueClass
79 @jdk.internal.ValueBased
80 public final class Integer extends Number
81 implements Comparable<Integer>, Constable, ConstantDesc {
82 /**
83 * A constant holding the minimum value an {@code int} can
84 * have, -2<sup>31</sup>.
85 */
86 @Native public static final int MIN_VALUE = 0x80000000;
87
88 /**
89 * A constant holding the maximum value an {@code int} can
90 * have, 2<sup>31</sup>-1.
91 */
92 @Native public static final int MAX_VALUE = 0x7fffffff;
93
94 /**
95 * The {@code Class} instance representing the primitive type
96 * {@code int}.
97 *
98 * @since 1.1
99 */
100 @SuppressWarnings("unchecked")
101 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
102
103 /**
104 * All possible chars for representing a number as a String
105 */
106 static final char[] digits = {
107 '0' , '1' , '2' , '3' , '4' , '5' ,
108 '6' , '7' , '8' , '9' , 'a' , 'b' ,
109 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
110 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
111 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
112 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
113 };
114
115 /**
116 * Returns a string representation of the first argument in the
117 * radix specified by the second argument.
118 *
119 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
120 * or larger than {@code Character.MAX_RADIX}, then the radix
121 * {@code 10} is used instead.
122 *
123 * <p>If the first argument is negative, the first element of the
124 * result is the ASCII minus character {@code '-'}
125 * ({@code '\u005Cu002D'}). If the first argument is not
126 * negative, no sign character appears in the result.
127 *
128 * <p>The remaining characters of the result represent the magnitude
129 * of the first argument. If the magnitude is zero, it is
130 * represented by a single zero character {@code '0'}
131 * ({@code '\u005Cu0030'}); otherwise, the first character of
132 * the representation of the magnitude will not be the zero
133 * character. The following ASCII characters are used as digits:
134 *
135 * <blockquote>
136 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
137 * </blockquote>
138 *
139 * These are {@code '\u005Cu0030'} through
140 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
141 * {@code '\u005Cu007A'}. If {@code radix} is
142 * <var>N</var>, then the first <var>N</var> of these characters
143 * are used as radix-<var>N</var> digits in the order shown. Thus,
144 * the digits for hexadecimal (radix 16) are
145 * {@code 0123456789abcdef}. If uppercase letters are
146 * desired, the {@link java.lang.String#toUpperCase()} method may
147 * be called on the result:
148 *
149 * <blockquote>
150 * {@code Integer.toString(n, 16).toUpperCase()}
151 * </blockquote>
152 *
153 * @param i an integer to be converted to a string.
154 * @param radix the radix to use in the string representation.
155 * @return a string representation of the argument in the specified radix.
156 * @see java.lang.Character#MAX_RADIX
157 * @see java.lang.Character#MIN_RADIX
158 */
159 public static String toString(int i, int radix) {
160 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
161 radix = 10;
162
163 /* Use the faster version */
164 if (radix == 10) {
165 return toString(i);
166 }
167
168 if (COMPACT_STRINGS) {
169 byte[] buf = new byte[33];
170 boolean negative = (i < 0);
171 int charPos = 32;
172
173 if (!negative) {
174 i = -i;
175 }
176
177 while (i <= -radix) {
178 buf[charPos--] = (byte)digits[-(i % radix)];
179 i = i / radix;
180 }
181 buf[charPos] = (byte)digits[-i];
182
183 if (negative) {
184 buf[--charPos] = '-';
185 }
186
187 return StringLatin1.newString(buf, charPos, (33 - charPos));
188 }
189 return toStringUTF16(i, radix);
190 }
191
192 private static String toStringUTF16(int i, int radix) {
193 byte[] buf = new byte[33 * 2];
194 boolean negative = (i < 0);
195 int charPos = 32;
196 if (!negative) {
197 i = -i;
198 }
199 while (i <= -radix) {
200 StringUTF16.putChar(buf, charPos--, digits[-(i % radix)]);
201 i = i / radix;
202 }
203 StringUTF16.putChar(buf, charPos, digits[-i]);
204
205 if (negative) {
206 StringUTF16.putChar(buf, --charPos, '-');
207 }
208 return StringUTF16.newString(buf, charPos, (33 - charPos));
209 }
210
211 /**
212 * Returns a string representation of the first argument as an
213 * unsigned integer value in the radix specified by the second
214 * argument.
215 *
216 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
217 * or larger than {@code Character.MAX_RADIX}, then the radix
218 * {@code 10} is used instead.
219 *
220 * <p>Note that since the first argument is treated as an unsigned
221 * value, no leading sign character is printed.
222 *
223 * <p>If the magnitude is zero, it is represented by a single zero
224 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
225 * the first character of the representation of the magnitude will
226 * not be the zero character.
227 *
228 * <p>The behavior of radixes and the characters used as digits
229 * are the same as {@link #toString(int, int) toString}.
230 *
231 * @param i an integer to be converted to an unsigned string.
232 * @param radix the radix to use in the string representation.
233 * @return an unsigned string representation of the argument in the specified radix.
234 * @see #toString(int, int)
235 * @since 1.8
236 */
237 public static String toUnsignedString(int i, int radix) {
238 return Long.toUnsignedString(toUnsignedLong(i), radix);
239 }
240
241 /**
242 * Returns a string representation of the integer argument as an
243 * unsigned integer in base 16.
244 *
245 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
246 * if the argument is negative; otherwise, it is equal to the
247 * argument. This value is converted to a string of ASCII digits
248 * in hexadecimal (base 16) with no extra leading
249 * {@code 0}s.
250 *
251 * <p>The value of the argument can be recovered from the returned
252 * string {@code s} by calling {@link
253 * Integer#parseUnsignedInt(String, int)
254 * Integer.parseUnsignedInt(s, 16)}.
255 *
256 * <p>If the unsigned magnitude is zero, it is represented by a
257 * single zero character {@code '0'} ({@code '\u005Cu0030'});
258 * otherwise, the first character of the representation of the
259 * unsigned magnitude will not be the zero character. The
260 * following characters are used as hexadecimal digits:
261 *
262 * <blockquote>
263 * {@code 0123456789abcdef}
264 * </blockquote>
265 *
266 * These are the characters {@code '\u005Cu0030'} through
267 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
268 * {@code '\u005Cu0066'}. If uppercase letters are
269 * desired, the {@link java.lang.String#toUpperCase()} method may
270 * be called on the result:
271 *
272 * <blockquote>
273 * {@code Integer.toHexString(n).toUpperCase()}
274 * </blockquote>
275 *
276 * @apiNote
277 * The {@link java.util.HexFormat} class provides formatting and parsing
278 * of byte arrays and primitives to return a string or adding to an {@link Appendable}.
279 * {@code HexFormat} formats and parses uppercase or lowercase hexadecimal characters,
280 * with leading zeros and for byte arrays includes for each byte
281 * a delimiter, prefix, and suffix.
282 *
283 * @param i an integer to be converted to a string.
284 * @return the string representation of the unsigned integer value
285 * represented by the argument in hexadecimal (base 16).
286 * @see java.util.HexFormat
287 * @see #parseUnsignedInt(String, int)
288 * @see #toUnsignedString(int, int)
289 * @since 1.0.2
290 */
291 public static String toHexString(int i) {
292 return toUnsignedString0(i, 4);
293 }
294
295 /**
296 * Returns a string representation of the integer argument as an
297 * unsigned integer in base 8.
298 *
299 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
300 * if the argument is negative; otherwise, it is equal to the
301 * argument. This value is converted to a string of ASCII digits
302 * in octal (base 8) with no extra leading {@code 0}s.
303 *
304 * <p>The value of the argument can be recovered from the returned
305 * string {@code s} by calling {@link
306 * Integer#parseUnsignedInt(String, int)
307 * Integer.parseUnsignedInt(s, 8)}.
308 *
309 * <p>If the unsigned magnitude is zero, it is represented by a
310 * single zero character {@code '0'} ({@code '\u005Cu0030'});
311 * otherwise, the first character of the representation of the
312 * unsigned magnitude will not be the zero character. The
313 * following characters are used as octal digits:
314 *
315 * <blockquote>
316 * {@code 01234567}
317 * </blockquote>
318 *
319 * These are the characters {@code '\u005Cu0030'} through
320 * {@code '\u005Cu0037'}.
321 *
322 * @param i an integer to be converted to a string.
323 * @return the string representation of the unsigned integer value
324 * represented by the argument in octal (base 8).
325 * @see #parseUnsignedInt(String, int)
326 * @see #toUnsignedString(int, int)
327 * @since 1.0.2
328 */
329 public static String toOctalString(int i) {
330 return toUnsignedString0(i, 3);
331 }
332
333 /**
334 * Returns a string representation of the integer argument as an
335 * unsigned integer in base 2.
336 *
337 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
338 * if the argument is negative; otherwise it is equal to the
339 * argument. This value is converted to a string of ASCII digits
340 * in binary (base 2) with no extra leading {@code 0}s.
341 *
342 * <p>The value of the argument can be recovered from the returned
343 * string {@code s} by calling {@link
344 * Integer#parseUnsignedInt(String, int)
345 * Integer.parseUnsignedInt(s, 2)}.
346 *
347 * <p>If the unsigned magnitude is zero, it is represented by a
348 * single zero character {@code '0'} ({@code '\u005Cu0030'});
349 * otherwise, the first character of the representation of the
350 * unsigned magnitude will not be the zero character. The
351 * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
352 * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
353 *
354 * @param i an integer to be converted to a string.
355 * @return the string representation of the unsigned integer value
356 * represented by the argument in binary (base 2).
357 * @see #parseUnsignedInt(String, int)
358 * @see #toUnsignedString(int, int)
359 * @since 1.0.2
360 */
361 public static String toBinaryString(int i) {
362 return toUnsignedString0(i, 1);
363 }
364
365 /**
366 * Convert the integer to an unsigned number.
367 */
368 private static String toUnsignedString0(int val, int shift) {
369 // assert shift > 0 && shift <=5 : "Illegal shift value";
370 int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
371 int chars = Math.max(((mag + (shift - 1)) / shift), 1);
372 if (COMPACT_STRINGS) {
373 byte[] buf = new byte[chars];
374 formatUnsignedInt(val, shift, buf, chars);
375 return new String(buf, LATIN1);
376 } else {
377 byte[] buf = new byte[chars * 2];
378 formatUnsignedIntUTF16(val, shift, buf, chars);
379 return new String(buf, UTF16);
380 }
381 }
382
383 /**
384 * Format an {@code int} (treated as unsigned) into a byte buffer (LATIN1 version). If
385 * {@code len} exceeds the formatted ASCII representation of {@code val},
386 * {@code buf} will be padded with leading zeroes.
387 *
388 * @param val the unsigned int to format
389 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
390 * @param buf the byte buffer to write to
391 * @param len the number of characters to write
392 */
393 private static void formatUnsignedInt(int val, int shift, byte[] buf, int len) {
394 int charPos = len;
395 int radix = 1 << shift;
396 int mask = radix - 1;
397 do {
398 buf[--charPos] = (byte)Integer.digits[val & mask];
399 val >>>= shift;
400 } while (charPos > 0);
401 }
402
403 /**
404 * Format an {@code int} (treated as unsigned) into a byte buffer (UTF16 version). If
405 * {@code len} exceeds the formatted ASCII representation of {@code val},
406 * {@code buf} will be padded with leading zeroes.
407 *
408 * @param val the unsigned int to format
409 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
410 * @param buf the byte buffer to write to
411 * @param len the number of characters to write
412 */
413 private static void formatUnsignedIntUTF16(int val, int shift, byte[] buf, int len) {
414 int charPos = len;
415 int radix = 1 << shift;
416 int mask = radix - 1;
417 do {
418 StringUTF16.putChar(buf, --charPos, Integer.digits[val & mask]);
419 val >>>= shift;
420 } while (charPos > 0);
421 }
422
423 /**
424 * Returns a {@code String} object representing the
425 * specified integer. The argument is converted to signed decimal
426 * representation and returned as a string, exactly as if the
427 * argument and radix 10 were given as arguments to the {@link
428 * #toString(int, int)} method.
429 *
430 * @param i an integer to be converted.
431 * @return a string representation of the argument in base 10.
432 */
433 @IntrinsicCandidate
434 public static String toString(int i) {
435 int size = DecimalDigits.stringSize(i);
436 if (COMPACT_STRINGS) {
437 byte[] buf = new byte[size];
438 StringLatin1.getChars(i, size, buf);
439 return new String(buf, LATIN1);
440 } else {
441 byte[] buf = new byte[size * 2];
442 StringUTF16.getChars(i, size, buf);
443 return new String(buf, UTF16);
444 }
445 }
446
447 /**
448 * Returns a string representation of the argument as an unsigned
449 * decimal value.
450 *
451 * The argument is converted to unsigned decimal representation
452 * and returned as a string exactly as if the argument and radix
453 * 10 were given as arguments to the {@link #toUnsignedString(int,
454 * int)} method.
455 *
456 * @param i an integer to be converted to an unsigned string.
457 * @return an unsigned string representation of the argument.
458 * @see #toUnsignedString(int, int)
459 * @since 1.8
460 */
461 public static String toUnsignedString(int i) {
462 return Long.toString(toUnsignedLong(i));
463 }
464
465 /**
466 * Parses the string argument as a signed integer in the radix
467 * specified by the second argument. The characters in the string
468 * must all be digits of the specified radix (as determined by
469 * whether {@link java.lang.Character#digit(char, int)} returns a
470 * nonnegative value), except that the first character may be an
471 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
472 * indicate a negative value or an ASCII plus sign {@code '+'}
473 * ({@code '\u005Cu002B'}) to indicate a positive value. The
474 * resulting integer value is returned.
475 *
476 * <p>An exception of type {@code NumberFormatException} is
477 * thrown if any of the following situations occurs:
478 * <ul>
479 * <li>The first argument is {@code null} or is a string of
480 * length zero.
481 *
482 * <li>The radix is either smaller than
483 * {@link java.lang.Character#MIN_RADIX} or
484 * larger than {@link java.lang.Character#MAX_RADIX}.
485 *
486 * <li>Any character of the string is not a digit of the specified
487 * radix, except that the first character may be a minus sign
488 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
489 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
490 * string is longer than length 1.
491 *
492 * <li>The value represented by the string is not a value of type
493 * {@code int}.
494 * </ul>
495 *
496 * <p>Examples:
497 * <blockquote><pre>
498 * parseInt("0", 10) returns 0
499 * parseInt("473", 10) returns 473
500 * parseInt("+42", 10) returns 42
501 * parseInt("-0", 10) returns 0
502 * parseInt("-FF", 16) returns -255
503 * parseInt("1100110", 2) returns 102
504 * parseInt("2147483647", 10) returns 2147483647
505 * parseInt("-2147483648", 10) returns -2147483648
506 * parseInt("2147483648", 10) throws a NumberFormatException
507 * parseInt("99", 8) throws a NumberFormatException
508 * parseInt("Kona", 10) throws a NumberFormatException
509 * parseInt("Kona", 27) returns 411787
510 * </pre></blockquote>
511 *
512 * @param s the {@code String} containing the integer
513 * representation to be parsed
514 * @param radix the radix to be used while parsing {@code s}.
515 * @return the integer represented by the string argument in the
516 * specified radix.
517 * @throws NumberFormatException if the {@code String}
518 * does not contain a parsable {@code int}.
519 */
520 public static int parseInt(String s, int radix)
521 throws NumberFormatException {
522 /*
523 * WARNING: This method may be invoked early during VM initialization
524 * before IntegerCache is initialized. Care must be taken to not use
525 * the valueOf method.
526 */
527
528 if (s == null) {
529 throw new NumberFormatException("Cannot parse null string");
530 }
531
532 if (radix < Character.MIN_RADIX) {
533 throw new NumberFormatException(String.format(
534 "radix %s less than Character.MIN_RADIX", radix));
535 }
536
537 if (radix > Character.MAX_RADIX) {
538 throw new NumberFormatException(String.format(
539 "radix %s greater than Character.MAX_RADIX", radix));
540 }
541
542 int len = s.length();
543 if (len == 0) {
544 throw NumberFormatException.forInputString("", radix);
545 }
546 int digit = ~0xFF;
547 int i = 0;
548 char firstChar = s.charAt(i++);
549 if (firstChar != '-' && firstChar != '+') {
550 digit = digit(firstChar, radix);
551 }
552 if (digit >= 0 || digit == ~0xFF && len > 1) {
553 int limit = firstChar != '-' ? MIN_VALUE + 1 : MIN_VALUE;
554 int multmin = limit / radix;
555 int result = -(digit & 0xFF);
556 boolean inRange = true;
557 /* Accumulating negatively avoids surprises near MAX_VALUE */
558 while (i < len && (digit = digit(s.charAt(i++), radix)) >= 0
559 && (inRange = result > multmin
560 || result == multmin && digit <= radix * multmin - limit)) {
561 result = radix * result - digit;
562 }
563 if (inRange && i == len && digit >= 0) {
564 return firstChar != '-' ? -result : result;
565 }
566 }
567 throw NumberFormatException.forInputString(s, radix);
568 }
569
570 /**
571 * Parses the {@link CharSequence} argument as a signed {@code int} in the
572 * specified {@code radix}, beginning at the specified {@code beginIndex}
573 * and extending to {@code endIndex - 1}.
574 *
575 * <p>The method does not take steps to guard against the
576 * {@code CharSequence} being mutated while parsing.
577 *
578 * @param s the {@code CharSequence} containing the {@code int}
579 * representation to be parsed
580 * @param beginIndex the beginning index, inclusive.
581 * @param endIndex the ending index, exclusive.
582 * @param radix the radix to be used while parsing {@code s}.
583 * @return the signed {@code int} represented by the subsequence in
584 * the specified radix.
585 * @throws NullPointerException if {@code s} is null.
586 * @throws IndexOutOfBoundsException if {@code beginIndex} is
587 * negative, or if {@code beginIndex} is greater than
588 * {@code endIndex} or if {@code endIndex} is greater than
589 * {@code s.length()}.
590 * @throws NumberFormatException if the {@code CharSequence} does not
591 * contain a parsable {@code int} in the specified
592 * {@code radix}, or if {@code radix} is either smaller than
593 * {@link java.lang.Character#MIN_RADIX} or larger than
594 * {@link java.lang.Character#MAX_RADIX}.
595 * @since 9
596 */
597 public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix)
598 throws NumberFormatException {
599 Objects.requireNonNull(s);
600 Objects.checkFromToIndex(beginIndex, endIndex, s.length());
601
602 if (radix < Character.MIN_RADIX) {
603 throw new NumberFormatException(String.format(
604 "radix %s less than Character.MIN_RADIX", radix));
605 }
606
607 if (radix > Character.MAX_RADIX) {
608 throw new NumberFormatException(String.format(
609 "radix %s greater than Character.MAX_RADIX", radix));
610 }
611
612 /*
613 * While s can be concurrently modified, it is ensured that each
614 * of its characters is read at most once, from lower to higher indices.
615 * This is obtained by reading them using the pattern s.charAt(i++),
616 * and by not updating i anywhere else.
617 */
618 if (beginIndex == endIndex) {
619 throw NumberFormatException.forInputString("", radix);
620 }
621 int digit = ~0xFF;
622 int i = beginIndex;
623 char firstChar = s.charAt(i++);
624 if (firstChar != '-' && firstChar != '+') {
625 digit = digit(firstChar, radix);
626 }
627 if (digit >= 0 || digit == ~0xFF && endIndex - beginIndex > 1) {
628 int limit = firstChar != '-' ? MIN_VALUE + 1 : MIN_VALUE;
629 int multmin = limit / radix;
630 int result = -(digit & 0xFF);
631 boolean inRange = true;
632 /* Accumulating negatively avoids surprises near MAX_VALUE */
633 while (i < endIndex && (digit = digit(s.charAt(i++), radix)) >= 0
634 && (inRange = result > multmin
635 || result == multmin && digit <= radix * multmin - limit)) {
636 result = radix * result - digit;
637 }
638 if (inRange && i == endIndex && digit >= 0) {
639 return firstChar != '-' ? -result : result;
640 }
641 }
642 throw NumberFormatException.forCharSequence(s, beginIndex,
643 endIndex, i - (digit < -1 ? 0 : 1));
644 }
645
646 /**
647 * Parses the string argument as a signed decimal integer. The
648 * characters in the string must all be decimal digits, except
649 * that the first character may be an ASCII minus sign {@code '-'}
650 * ({@code '\u005Cu002D'}) to indicate a negative value or an
651 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
652 * indicate a positive value. The resulting integer value is
653 * returned, exactly as if the argument and the radix 10 were
654 * given as arguments to the {@link #parseInt(java.lang.String,
655 * int)} method.
656 *
657 * @param s a {@code String} containing the {@code int}
658 * representation to be parsed
659 * @return the integer value represented by the argument in decimal.
660 * @throws NumberFormatException if the string does not contain a
661 * parsable integer.
662 */
663 public static int parseInt(String s) throws NumberFormatException {
664 return parseInt(s, 10);
665 }
666
667 /**
668 * Parses the string argument as an unsigned integer in the radix
669 * specified by the second argument. An unsigned integer maps the
670 * values usually associated with negative numbers to positive
671 * numbers larger than {@code MAX_VALUE}.
672 *
673 * The characters in the string must all be digits of the
674 * specified radix (as determined by whether {@link
675 * java.lang.Character#digit(char, int)} returns a nonnegative
676 * value), except that the first character may be an ASCII plus
677 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
678 * integer value is returned.
679 *
680 * <p>An exception of type {@code NumberFormatException} is
681 * thrown if any of the following situations occurs:
682 * <ul>
683 * <li>The first argument is {@code null} or is a string of
684 * length zero.
685 *
686 * <li>The radix is either smaller than
687 * {@link java.lang.Character#MIN_RADIX} or
688 * larger than {@link java.lang.Character#MAX_RADIX}.
689 *
690 * <li>Any character of the string is not a digit of the specified
691 * radix, except that the first character may be a plus sign
692 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
693 * string is longer than length 1.
694 *
695 * <li>The value represented by the string is larger than the
696 * largest unsigned {@code int}, 2<sup>32</sup>-1.
697 *
698 * </ul>
699 *
700 *
701 * @param s the {@code String} containing the unsigned integer
702 * representation to be parsed
703 * @param radix the radix to be used while parsing {@code s}.
704 * @return the integer represented by the string argument in the
705 * specified radix.
706 * @throws NumberFormatException if the {@code String}
707 * does not contain a parsable {@code int}.
708 * @since 1.8
709 */
710 public static int parseUnsignedInt(String s, int radix)
711 throws NumberFormatException {
712 if (s == null) {
713 throw new NumberFormatException("Cannot parse null string");
714 }
715
716 if (radix < Character.MIN_RADIX) {
717 throw new NumberFormatException(String.format(
718 "radix %s less than Character.MIN_RADIX", radix));
719 }
720
721 if (radix > Character.MAX_RADIX) {
722 throw new NumberFormatException(String.format(
723 "radix %s greater than Character.MAX_RADIX", radix));
724 }
725
726 int len = s.length();
727 if (len == 0) {
728 throw NumberFormatException.forInputString(s, radix);
729 }
730 int i = 0;
731 char firstChar = s.charAt(i++);
732 if (firstChar == '-') {
733 throw new NumberFormatException(String.format(
734 "Illegal leading minus sign on unsigned string %s.", s));
735 }
736 int digit = ~0xFF;
737 if (firstChar != '+') {
738 digit = digit(firstChar, radix);
739 }
740 if (digit >= 0 || digit == ~0xFF && len > 1) {
741 int multmax = divideUnsigned(-1, radix); // -1 is max unsigned int
742 int result = digit & 0xFF;
743 boolean inRange = true;
744 while (i < len && (digit = digit(s.charAt(i++), radix)) >= 0
745 && (inRange = compareUnsigned(result, multmax) < 0
746 || result == multmax && digit < -radix * multmax)) {
747 result = radix * result + digit;
748 }
749 if (inRange && i == len && digit >= 0) {
750 return result;
751 }
752 }
753 if (digit < 0) {
754 throw NumberFormatException.forInputString(s, radix);
755 }
756 throw new NumberFormatException(String.format(
757 "String value %s exceeds range of unsigned int.", s));
758 }
759
760 /**
761 * Parses the {@link CharSequence} argument as an unsigned {@code int} in
762 * the specified {@code radix}, beginning at the specified
763 * {@code beginIndex} and extending to {@code endIndex - 1}.
764 *
765 * <p>The method does not take steps to guard against the
766 * {@code CharSequence} being mutated while parsing.
767 *
768 * @param s the {@code CharSequence} containing the unsigned
769 * {@code int} representation to be parsed
770 * @param beginIndex the beginning index, inclusive.
771 * @param endIndex the ending index, exclusive.
772 * @param radix the radix to be used while parsing {@code s}.
773 * @return the unsigned {@code int} represented by the subsequence in
774 * the specified radix.
775 * @throws NullPointerException if {@code s} is null.
776 * @throws IndexOutOfBoundsException if {@code beginIndex} is
777 * negative, or if {@code beginIndex} is greater than
778 * {@code endIndex} or if {@code endIndex} is greater than
779 * {@code s.length()}.
780 * @throws NumberFormatException if the {@code CharSequence} does not
781 * contain a parsable unsigned {@code int} in the specified
782 * {@code radix}, or if {@code radix} is either smaller than
783 * {@link java.lang.Character#MIN_RADIX} or larger than
784 * {@link java.lang.Character#MAX_RADIX}.
785 * @since 9
786 */
787 public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix)
788 throws NumberFormatException {
789 Objects.requireNonNull(s);
790 Objects.checkFromToIndex(beginIndex, endIndex, s.length());
791
792 if (radix < Character.MIN_RADIX) {
793 throw new NumberFormatException(String.format(
794 "radix %s less than Character.MIN_RADIX", radix));
795 }
796
797 if (radix > Character.MAX_RADIX) {
798 throw new NumberFormatException(String.format(
799 "radix %s greater than Character.MAX_RADIX", radix));
800 }
801
802 /*
803 * While s can be concurrently modified, it is ensured that each
804 * of its characters is read at most once, from lower to higher indices.
805 * This is obtained by reading them using the pattern s.charAt(i++),
806 * and by not updating i anywhere else.
807 */
808 if (beginIndex == endIndex) {
809 throw NumberFormatException.forInputString("", radix);
810 }
811 int i = beginIndex;
812 char firstChar = s.charAt(i++);
813 if (firstChar == '-') {
814 throw new NumberFormatException(
815 "Illegal leading minus sign on unsigned string " + s + ".");
816 }
817 int digit = ~0xFF;
818 if (firstChar != '+') {
819 digit = digit(firstChar, radix);
820 }
821 if (digit >= 0 || digit == ~0xFF && endIndex - beginIndex > 1) {
822 int multmax = divideUnsigned(-1, radix); // -1 is max unsigned int
823 int result = digit & 0xFF;
824 boolean inRange = true;
825 while (i < endIndex && (digit = digit(s.charAt(i++), radix)) >= 0
826 && (inRange = compareUnsigned(result, multmax) < 0
827 || result == multmax && digit < -radix * multmax)) {
828 result = radix * result + digit;
829 }
830 if (inRange && i == endIndex && digit >= 0) {
831 return result;
832 }
833 }
834 if (digit < 0) {
835 throw NumberFormatException.forCharSequence(s, beginIndex,
836 endIndex, i - (digit < -1 ? 0 : 1));
837 }
838 throw new NumberFormatException(String.format(
839 "String value %s exceeds range of unsigned int.", s));
840 }
841
842 /**
843 * Parses the string argument as an unsigned decimal integer. The
844 * characters in the string must all be decimal digits, except
845 * that the first character may be an ASCII plus sign {@code
846 * '+'} ({@code '\u005Cu002B'}). The resulting integer value
847 * is returned, exactly as if the argument and the radix 10 were
848 * given as arguments to the {@link
849 * #parseUnsignedInt(java.lang.String, int)} method.
850 *
851 * @param s a {@code String} containing the unsigned {@code int}
852 * representation to be parsed
853 * @return the unsigned integer value represented by the argument in decimal.
854 * @throws NumberFormatException if the string does not contain a
855 * parsable unsigned integer.
856 * @since 1.8
857 */
858 public static int parseUnsignedInt(String s) throws NumberFormatException {
859 return parseUnsignedInt(s, 10);
860 }
861
862 /**
863 * Returns an {@code Integer} object holding the value
864 * extracted from the specified {@code String} when parsed
865 * with the radix given by the second argument. The first argument
866 * is interpreted as representing a signed integer in the radix
867 * specified by the second argument, exactly as if the arguments
868 * were given to the {@link #parseInt(java.lang.String, int)}
869 * method. The result is an {@code Integer} object that
870 * represents the integer value specified by the string.
871 *
872 * <p>In other words, this method returns an {@code Integer}
873 * object equal to the value of:
874 *
875 * <blockquote>
876 * {@code Integer.valueOf(Integer.parseInt(s, radix))}
877 * </blockquote>
878 *
879 * @param s the string to be parsed.
880 * @param radix the radix to be used in interpreting {@code s}
881 * @return an {@code Integer} object holding the value
882 * represented by the string argument in the specified
883 * radix.
884 * @throws NumberFormatException if the {@code String}
885 * does not contain a parsable {@code int}.
886 */
887 public static Integer valueOf(String s, int radix) throws NumberFormatException {
888 return Integer.valueOf(parseInt(s,radix));
889 }
890
891 /**
892 * Returns an {@code Integer} object holding the
893 * value of the specified {@code String}. The argument is
894 * interpreted as representing a signed decimal integer, exactly
895 * as if the argument were given to the {@link
896 * #parseInt(java.lang.String)} method. The result is an
897 * {@code Integer} object that represents the integer value
898 * specified by the string.
899 *
900 * <p>In other words, this method returns an {@code Integer}
901 * object equal to the value of:
902 *
903 * <blockquote>
904 * {@code Integer.valueOf(Integer.parseInt(s))}
905 * </blockquote>
906 *
907 * @param s the string to be parsed.
908 * @return an {@code Integer} object holding the value
909 * represented by the string argument.
910 * @throws NumberFormatException if the string cannot be parsed
911 * as an integer.
912 */
913 public static Integer valueOf(String s) throws NumberFormatException {
914 return Integer.valueOf(parseInt(s, 10));
915 }
916
917 /**
918 * Cache to support the object identity semantics of autoboxing for values between
919 * -128 and 127 (inclusive) as required by JLS.
920 *
921 * The cache is initialized on first usage. The size of the cache
922 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
923 * During VM initialization, java.lang.Integer.IntegerCache.high property
924 * may be set and saved in the private system properties in the
925 * jdk.internal.misc.VM class.
926 *
927 * WARNING: The cache is archived with CDS and reloaded from the shared
928 * archive at runtime. The archived cache (Integer[]) and Integer objects
929 * reside in the closed archive heap regions. Care should be taken when
930 * changing the implementation and the cache array should not be assigned
931 * with new Integer object(s) after initialization.
932 */
933
934 private static final class IntegerCache {
935 static final int low = -128;
936 static final int high;
937
938 @Stable
939 static final Integer[] cache;
940 static Integer[] archivedCache;
941
942 static {
943 // high value may be configured by property
944 int h = 127;
945 String integerCacheHighPropValue =
946 VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
947 if (integerCacheHighPropValue != null) {
948 try {
949 h = Math.max(parseInt(integerCacheHighPropValue), 127);
950 // Maximum array size is Integer.MAX_VALUE
951 h = Math.min(h, Integer.MAX_VALUE - (-low) -1);
952 } catch( NumberFormatException nfe) {
953 // If the property cannot be parsed into an int, ignore it.
954 }
955 }
956 high = h;
957
958 // Load IntegerCache.archivedCache from archive, if possible
959 CDS.initializeFromArchive(IntegerCache.class);
960 int size = (high - low) + 1;
961
962 // Use the archived cache if it exists and is large enough
963 if (archivedCache == null || size > archivedCache.length) {
964 Integer[] c = new Integer[size];
965 int j = low;
966 for(int i = 0; i < c.length; i++) {
967 c[i] = new Integer(j++);
968 }
969 archivedCache = c;
970 }
971 cache = archivedCache;
972 // range [-128, 127] must be interned (JLS7 5.1.7)
973 assert IntegerCache.high >= 127;
974 }
975
976 private IntegerCache() {}
977 }
978
979 /**
980 * Returns an {@code Integer} instance representing the specified
981 * {@code int} value. If a new {@code Integer} instance is not
982 * required, this method should generally be used in preference to
983 * the constructor {@link #Integer(int)}, as this method is likely
984 * to yield significantly better space and time performance by
985 * caching frequently requested values.
986 *
987 * This method will always cache values in the range -128 to 127,
988 * inclusive, and may cache other values outside of this range.
989 *
990 * @param i an {@code int} value.
991 * @return an {@code Integer} instance representing {@code i}.
992 * @since 1.5
993 */
994 @IntrinsicCandidate
995 @DeserializeConstructor
996 public static Integer valueOf(int i) {
997 if (i >= IntegerCache.low && i <= IntegerCache.high)
998 return IntegerCache.cache[i + (-IntegerCache.low)];
999 return new Integer(i);
1000 }
1001
1002 /**
1003 * The value of the {@code Integer}.
1004 *
1005 * @serial
1006 */
1007 private final int value;
1008
1009 /**
1010 * Constructs a newly allocated {@code Integer} object that
1011 * represents the specified {@code int} value.
1012 *
1013 * @param value the value to be represented by the
1014 * {@code Integer} object.
1015 *
1016 * @deprecated
1017 * It is rarely appropriate to use this constructor. The static factory
1018 * {@link #valueOf(int)} is generally a better choice, as it is
1019 * likely to yield significantly better space and time performance.
1020 */
1021 @Deprecated(since="9", forRemoval = true)
1022 public Integer(int value) {
1023 this.value = value;
1024 }
1025
1026 /**
1027 * Constructs a newly allocated {@code Integer} object that
1028 * represents the {@code int} value indicated by the
1029 * {@code String} parameter. The string is converted to an
1030 * {@code int} value in exactly the manner used by the
1031 * {@code parseInt} method for radix 10.
1032 *
1033 * @param s the {@code String} to be converted to an {@code Integer}.
1034 * @throws NumberFormatException if the {@code String} does not
1035 * contain a parsable integer.
1036 *
1037 * @deprecated
1038 * It is rarely appropriate to use this constructor.
1039 * Use {@link #parseInt(String)} to convert a string to a
1040 * {@code int} primitive, or use {@link #valueOf(String)}
1041 * to convert a string to an {@code Integer} object.
1042 */
1043 @Deprecated(since="9", forRemoval = true)
1044 public Integer(String s) throws NumberFormatException {
1045 this.value = parseInt(s, 10);
1046 }
1047
1048 /**
1049 * Returns the value of this {@code Integer} as a {@code byte}
1050 * after a narrowing primitive conversion.
1051 * @jls 5.1.3 Narrowing Primitive Conversion
1052 */
1053 public byte byteValue() {
1054 return (byte)value;
1055 }
1056
1057 /**
1058 * Returns the value of this {@code Integer} as a {@code short}
1059 * after a narrowing primitive conversion.
1060 * @jls 5.1.3 Narrowing Primitive Conversion
1061 */
1062 public short shortValue() {
1063 return (short)value;
1064 }
1065
1066 /**
1067 * Returns the value of this {@code Integer} as an
1068 * {@code int}.
1069 */
1070 @IntrinsicCandidate
1071 public int intValue() {
1072 return value;
1073 }
1074
1075 /**
1076 * Returns the value of this {@code Integer} as a {@code long}
1077 * after a widening primitive conversion.
1078 * @jls 5.1.2 Widening Primitive Conversion
1079 * @see Integer#toUnsignedLong(int)
1080 */
1081 public long longValue() {
1082 return (long)value;
1083 }
1084
1085 /**
1086 * Returns the value of this {@code Integer} as a {@code float}
1087 * after a widening primitive conversion.
1088 * @jls 5.1.2 Widening Primitive Conversion
1089 */
1090 public float floatValue() {
1091 return (float)value;
1092 }
1093
1094 /**
1095 * Returns the value of this {@code Integer} as a {@code double}
1096 * after a widening primitive conversion.
1097 * @jls 5.1.2 Widening Primitive Conversion
1098 */
1099 public double doubleValue() {
1100 return (double)value;
1101 }
1102
1103 /**
1104 * Returns a {@code String} object representing this
1105 * {@code Integer}'s value. The value is converted to signed
1106 * decimal representation and returned as a string, exactly as if
1107 * the integer value were given as an argument to the {@link
1108 * java.lang.Integer#toString(int)} method.
1109 *
1110 * @return a string representation of the value of this object in
1111 * base 10.
1112 */
1113 public String toString() {
1114 return toString(value);
1115 }
1116
1117 /**
1118 * Returns a hash code for this {@code Integer}.
1119 *
1120 * @return a hash code value for this object, equal to the
1121 * primitive {@code int} value represented by this
1122 * {@code Integer} object.
1123 */
1124 @Override
1125 public int hashCode() {
1126 return Integer.hashCode(value);
1127 }
1128
1129 /**
1130 * Returns a hash code for an {@code int} value; compatible with
1131 * {@code Integer.hashCode()}.
1132 *
1133 * @param value the value to hash
1134 * @since 1.8
1135 *
1136 * @return a hash code value for an {@code int} value.
1137 */
1138 public static int hashCode(int value) {
1139 return value;
1140 }
1141
1142 /**
1143 * Compares this object to the specified object. The result is
1144 * {@code true} if and only if the argument is not
1145 * {@code null} and is an {@code Integer} object that
1146 * contains the same {@code int} value as this object.
1147 *
1148 * @param obj the object to compare with.
1149 * @return {@code true} if the objects are the same;
1150 * {@code false} otherwise.
1151 */
1152 public boolean equals(Object obj) {
1153 if (obj instanceof Integer) {
1154 return value == ((Integer)obj).intValue();
1155 }
1156 return false;
1157 }
1158
1159 /**
1160 * Determines the integer value of the system property with the
1161 * specified name.
1162 *
1163 * <p>The first argument is treated as the name of a system
1164 * property. System properties are accessible through the {@link
1165 * java.lang.System#getProperty(java.lang.String)} method. The
1166 * string value of this property is then interpreted as an integer
1167 * value using the grammar supported by {@link Integer#decode decode} and
1168 * an {@code Integer} object representing this value is returned.
1169 *
1170 * <p>If there is no property with the specified name, if the
1171 * specified name is empty or {@code null}, or if the property
1172 * does not have the correct numeric format, then {@code null} is
1173 * returned.
1174 *
1175 * <p>In other words, this method returns an {@code Integer}
1176 * object equal to the value of:
1177 *
1178 * <blockquote>
1179 * {@code getInteger(nm, null)}
1180 * </blockquote>
1181 *
1182 * @param nm property name.
1183 * @return the {@code Integer} value of the property.
1184 * @throws SecurityException for the same reasons as
1185 * {@link System#getProperty(String) System.getProperty}
1186 * @see java.lang.System#getProperty(java.lang.String)
1187 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1188 */
1189 public static Integer getInteger(String nm) {
1190 return getInteger(nm, null);
1191 }
1192
1193 /**
1194 * Determines the integer value of the system property with the
1195 * specified name.
1196 *
1197 * <p>The first argument is treated as the name of a system
1198 * property. System properties are accessible through the {@link
1199 * java.lang.System#getProperty(java.lang.String)} method. The
1200 * string value of this property is then interpreted as an integer
1201 * value using the grammar supported by {@link Integer#decode decode} and
1202 * an {@code Integer} object representing this value is returned.
1203 *
1204 * <p>The second argument is the default value. An {@code Integer} object
1205 * that represents the value of the second argument is returned if there
1206 * is no property of the specified name, if the property does not have
1207 * the correct numeric format, or if the specified name is empty or
1208 * {@code null}.
1209 *
1210 * <p>In other words, this method returns an {@code Integer} object
1211 * equal to the value of:
1212 *
1213 * <blockquote>
1214 * {@code getInteger(nm, Integer.valueOf(val))}
1215 * </blockquote>
1216 *
1217 * but in practice it may be implemented in a manner such as:
1218 *
1219 * <blockquote><pre>
1220 * Integer result = getInteger(nm, null);
1221 * return (result == null) ? Integer.valueOf(val) : result;
1222 * </pre></blockquote>
1223 *
1224 * to avoid the unnecessary allocation of an {@code Integer}
1225 * object when the default value is not needed.
1226 *
1227 * @param nm property name.
1228 * @param val default value.
1229 * @return the {@code Integer} value of the property.
1230 * @throws SecurityException for the same reasons as
1231 * {@link System#getProperty(String) System.getProperty}
1232 * @see java.lang.System#getProperty(java.lang.String)
1233 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1234 */
1235 public static Integer getInteger(String nm, int val) {
1236 Integer result = getInteger(nm, null);
1237 return (result == null) ? Integer.valueOf(val) : result;
1238 }
1239
1240 /**
1241 * Returns the integer value of the system property with the
1242 * specified name. The first argument is treated as the name of a
1243 * system property. System properties are accessible through the
1244 * {@link java.lang.System#getProperty(java.lang.String)} method.
1245 * The string value of this property is then interpreted as an
1246 * integer value, as per the {@link Integer#decode decode} method,
1247 * and an {@code Integer} object representing this value is
1248 * returned; in summary:
1249 *
1250 * <ul><li>If the property value begins with the two ASCII characters
1251 * {@code 0x} or the ASCII character {@code #}, not
1252 * followed by a minus sign, then the rest of it is parsed as a
1253 * hexadecimal integer exactly as by the method
1254 * {@link #valueOf(java.lang.String, int)} with radix 16.
1255 * <li>If the property value begins with the ASCII character
1256 * {@code 0} followed by another character, it is parsed as an
1257 * octal integer exactly as by the method
1258 * {@link #valueOf(java.lang.String, int)} with radix 8.
1259 * <li>Otherwise, the property value is parsed as a decimal integer
1260 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1261 * with radix 10.
1262 * </ul>
1263 *
1264 * <p>The second argument is the default value. The default value is
1265 * returned if there is no property of the specified name, if the
1266 * property does not have the correct numeric format, or if the
1267 * specified name is empty or {@code null}.
1268 *
1269 * @param nm property name.
1270 * @param val default value.
1271 * @return the {@code Integer} value of the property.
1272 * @throws SecurityException for the same reasons as
1273 * {@link System#getProperty(String) System.getProperty}
1274 * @see System#getProperty(java.lang.String)
1275 * @see System#getProperty(java.lang.String, java.lang.String)
1276 */
1277 public static Integer getInteger(String nm, Integer val) {
1278 String v = null;
1279 try {
1280 v = System.getProperty(nm);
1281 } catch (IllegalArgumentException | NullPointerException e) {
1282 }
1283 if (v != null) {
1284 try {
1285 return Integer.decode(v);
1286 } catch (NumberFormatException e) {
1287 }
1288 }
1289 return val;
1290 }
1291
1292 /**
1293 * Decodes a {@code String} into an {@code Integer}.
1294 * Accepts decimal, hexadecimal, and octal numbers given
1295 * by the following grammar:
1296 *
1297 * <blockquote>
1298 * <dl>
1299 * <dt><i>DecodableString:</i>
1300 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1301 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1302 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1303 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1304 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1305 *
1306 * <dt><i>Sign:</i>
1307 * <dd>{@code -}
1308 * <dd>{@code +}
1309 * </dl>
1310 * </blockquote>
1311 *
1312 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1313 * are as defined in section {@jls 3.10.1} of
1314 * <cite>The Java Language Specification</cite>,
1315 * except that underscores are not accepted between digits.
1316 *
1317 * <p>The sequence of characters following an optional
1318 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1319 * "{@code #}", or leading zero) is parsed as by the {@code
1320 * Integer.parseInt} method with the indicated radix (10, 16, or
1321 * 8). This sequence of characters must represent a positive
1322 * value or a {@link NumberFormatException} will be thrown. The
1323 * result is negated if first character of the specified {@code
1324 * String} is the minus sign. No whitespace characters are
1325 * permitted in the {@code String}.
1326 *
1327 * @param nm the {@code String} to decode.
1328 * @return an {@code Integer} object holding the {@code int}
1329 * value represented by {@code nm}
1330 * @throws NumberFormatException if the {@code String} does not
1331 * contain a parsable integer.
1332 * @see java.lang.Integer#parseInt(java.lang.String, int)
1333 */
1334 public static Integer decode(String nm) throws NumberFormatException {
1335 int radix = 10;
1336 int index = 0;
1337 boolean negative = false;
1338 int result;
1339
1340 if (nm.isEmpty())
1341 throw new NumberFormatException("Zero length string");
1342 char firstChar = nm.charAt(0);
1343 // Handle sign, if present
1344 if (firstChar == '-') {
1345 negative = true;
1346 index++;
1347 } else if (firstChar == '+')
1348 index++;
1349
1350 // Handle radix specifier, if present
1351 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1352 index += 2;
1353 radix = 16;
1354 }
1355 else if (nm.startsWith("#", index)) {
1356 index ++;
1357 radix = 16;
1358 }
1359 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1360 index ++;
1361 radix = 8;
1362 }
1363
1364 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1365 throw new NumberFormatException("Sign character in wrong position");
1366
1367 try {
1368 result = parseInt(nm, index, nm.length(), radix);
1369 result = negative ? -result : result;
1370 } catch (NumberFormatException e) {
1371 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1372 // handles this case, and causes any genuine format error to be
1373 // rethrown.
1374 String constant = negative ? ("-" + nm.substring(index))
1375 : nm.substring(index);
1376 result = parseInt(constant, radix);
1377 }
1378 return result;
1379 }
1380
1381 /**
1382 * Compares two {@code Integer} objects numerically.
1383 *
1384 * @param anotherInteger the {@code Integer} to be compared.
1385 * @return the value {@code 0} if this {@code Integer} is
1386 * equal to the argument {@code Integer}; a value less than
1387 * {@code 0} if this {@code Integer} is numerically less
1388 * than the argument {@code Integer}; and a value greater
1389 * than {@code 0} if this {@code Integer} is numerically
1390 * greater than the argument {@code Integer} (signed
1391 * comparison).
1392 * @since 1.2
1393 */
1394 public int compareTo(Integer anotherInteger) {
1395 return compare(this.value, anotherInteger.value);
1396 }
1397
1398 /**
1399 * Compares two {@code int} values numerically.
1400 * The value returned is identical to what would be returned by:
1401 * <pre>
1402 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1403 * </pre>
1404 *
1405 * @param x the first {@code int} to compare
1406 * @param y the second {@code int} to compare
1407 * @return the value {@code 0} if {@code x == y};
1408 * a value less than {@code 0} if {@code x < y}; and
1409 * a value greater than {@code 0} if {@code x > y}
1410 * @since 1.7
1411 */
1412 public static int compare(int x, int y) {
1413 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1414 }
1415
1416 /**
1417 * Compares two {@code int} values numerically treating the values
1418 * as unsigned.
1419 *
1420 * @param x the first {@code int} to compare
1421 * @param y the second {@code int} to compare
1422 * @return the value {@code 0} if {@code x == y}; a value less
1423 * than {@code 0} if {@code x < y} as unsigned values; and
1424 * a value greater than {@code 0} if {@code x > y} as
1425 * unsigned values
1426 * @since 1.8
1427 */
1428 @IntrinsicCandidate
1429 public static int compareUnsigned(int x, int y) {
1430 return compare(x + MIN_VALUE, y + MIN_VALUE);
1431 }
1432
1433 /**
1434 * Converts the argument to a {@code long} by an unsigned
1435 * conversion. In an unsigned conversion to a {@code long}, the
1436 * high-order 32 bits of the {@code long} are zero and the
1437 * low-order 32 bits are equal to the bits of the integer
1438 * argument.
1439 *
1440 * Consequently, zero and positive {@code int} values are mapped
1441 * to a numerically equal {@code long} value and negative {@code
1442 * int} values are mapped to a {@code long} value equal to the
1443 * input plus 2<sup>32</sup>.
1444 *
1445 * @param x the value to convert to an unsigned {@code long}
1446 * @return the argument converted to {@code long} by an unsigned
1447 * conversion
1448 * @since 1.8
1449 */
1450 public static long toUnsignedLong(int x) {
1451 return ((long) x) & 0xffffffffL;
1452 }
1453
1454 /**
1455 * Returns the unsigned quotient of dividing the first argument by
1456 * the second where each argument and the result is interpreted as
1457 * an unsigned value.
1458 *
1459 * <p>Note that in two's complement arithmetic, the three other
1460 * basic arithmetic operations of add, subtract, and multiply are
1461 * bit-wise identical if the two operands are regarded as both
1462 * being signed or both being unsigned. Therefore separate {@code
1463 * addUnsigned}, etc. methods are not provided.
1464 *
1465 * @param dividend the value to be divided
1466 * @param divisor the value doing the dividing
1467 * @return the unsigned quotient of the first argument divided by
1468 * the second argument
1469 * @see #remainderUnsigned
1470 * @since 1.8
1471 */
1472 @IntrinsicCandidate
1473 public static int divideUnsigned(int dividend, int divisor) {
1474 // In lieu of tricky code, for now just use long arithmetic.
1475 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1476 }
1477
1478 /**
1479 * Returns the unsigned remainder from dividing the first argument
1480 * by the second where each argument and the result is interpreted
1481 * as an unsigned value.
1482 *
1483 * @param dividend the value to be divided
1484 * @param divisor the value doing the dividing
1485 * @return the unsigned remainder of the first argument divided by
1486 * the second argument
1487 * @see #divideUnsigned
1488 * @since 1.8
1489 */
1490 @IntrinsicCandidate
1491 public static int remainderUnsigned(int dividend, int divisor) {
1492 // In lieu of tricky code, for now just use long arithmetic.
1493 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1494 }
1495
1496
1497 // Bit twiddling
1498
1499 /**
1500 * The number of bits used to represent an {@code int} value in two's
1501 * complement binary form.
1502 *
1503 * @since 1.5
1504 */
1505 @Native public static final int SIZE = 32;
1506
1507 /**
1508 * The number of bytes used to represent an {@code int} value in two's
1509 * complement binary form.
1510 *
1511 * @since 1.8
1512 */
1513 public static final int BYTES = SIZE / Byte.SIZE;
1514
1515 /**
1516 * Returns an {@code int} value with at most a single one-bit, in the
1517 * position of the highest-order ("leftmost") one-bit in the specified
1518 * {@code int} value. Returns zero if the specified value has no
1519 * one-bits in its two's complement binary representation, that is, if it
1520 * is equal to zero.
1521 *
1522 * @param i the value whose highest one bit is to be computed
1523 * @return an {@code int} value with a single one-bit, in the position
1524 * of the highest-order one-bit in the specified value, or zero if
1525 * the specified value is itself equal to zero.
1526 * @since 1.5
1527 */
1528 public static int highestOneBit(int i) {
1529 return i & (MIN_VALUE >>> numberOfLeadingZeros(i));
1530 }
1531
1532 /**
1533 * Returns an {@code int} value with at most a single one-bit, in the
1534 * position of the lowest-order ("rightmost") one-bit in the specified
1535 * {@code int} value. Returns zero if the specified value has no
1536 * one-bits in its two's complement binary representation, that is, if it
1537 * is equal to zero.
1538 *
1539 * @param i the value whose lowest one bit is to be computed
1540 * @return an {@code int} value with a single one-bit, in the position
1541 * of the lowest-order one-bit in the specified value, or zero if
1542 * the specified value is itself equal to zero.
1543 * @since 1.5
1544 */
1545 public static int lowestOneBit(int i) {
1546 // HD, Section 2-1
1547 return i & -i;
1548 }
1549
1550 /**
1551 * Returns the number of zero bits preceding the highest-order
1552 * ("leftmost") one-bit in the two's complement binary representation
1553 * of the specified {@code int} value. Returns 32 if the
1554 * specified value has no one-bits in its two's complement representation,
1555 * in other words if it is equal to zero.
1556 *
1557 * <p>Note that this method is closely related to the logarithm base 2.
1558 * For all positive {@code int} values x:
1559 * <ul>
1560 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1561 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1562 * </ul>
1563 *
1564 * @param i the value whose number of leading zeros is to be computed
1565 * @return the number of zero bits preceding the highest-order
1566 * ("leftmost") one-bit in the two's complement binary representation
1567 * of the specified {@code int} value, or 32 if the value
1568 * is equal to zero.
1569 * @since 1.5
1570 */
1571 @IntrinsicCandidate
1572 public static int numberOfLeadingZeros(int i) {
1573 // HD, Count leading 0's
1574 if (i <= 0)
1575 return i == 0 ? 32 : 0;
1576 int n = 31;
1577 if (i >= 1 << 16) { n -= 16; i >>>= 16; }
1578 if (i >= 1 << 8) { n -= 8; i >>>= 8; }
1579 if (i >= 1 << 4) { n -= 4; i >>>= 4; }
1580 if (i >= 1 << 2) { n -= 2; i >>>= 2; }
1581 return n - (i >>> 1);
1582 }
1583
1584 /**
1585 * Returns the number of zero bits following the lowest-order ("rightmost")
1586 * one-bit in the two's complement binary representation of the specified
1587 * {@code int} value. Returns 32 if the specified value has no
1588 * one-bits in its two's complement representation, in other words if it is
1589 * equal to zero.
1590 *
1591 * @param i the value whose number of trailing zeros is to be computed
1592 * @return the number of zero bits following the lowest-order ("rightmost")
1593 * one-bit in the two's complement binary representation of the
1594 * specified {@code int} value, or 32 if the value is equal
1595 * to zero.
1596 * @since 1.5
1597 */
1598 @IntrinsicCandidate
1599 public static int numberOfTrailingZeros(int i) {
1600 // HD, Count trailing 0's
1601 i = ~i & (i - 1);
1602 if (i <= 0) return i & 32;
1603 int n = 1;
1604 if (i > 1 << 16) { n += 16; i >>>= 16; }
1605 if (i > 1 << 8) { n += 8; i >>>= 8; }
1606 if (i > 1 << 4) { n += 4; i >>>= 4; }
1607 if (i > 1 << 2) { n += 2; i >>>= 2; }
1608 return n + (i >>> 1);
1609 }
1610
1611 /**
1612 * Returns the number of one-bits in the two's complement binary
1613 * representation of the specified {@code int} value. This function is
1614 * sometimes referred to as the <i>population count</i>.
1615 *
1616 * @param i the value whose bits are to be counted
1617 * @return the number of one-bits in the two's complement binary
1618 * representation of the specified {@code int} value.
1619 * @since 1.5
1620 */
1621 @IntrinsicCandidate
1622 public static int bitCount(int i) {
1623 // HD, Figure 5-2
1624 i = i - ((i >>> 1) & 0x55555555);
1625 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1626 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1627 i = i + (i >>> 8);
1628 i = i + (i >>> 16);
1629 return i & 0x3f;
1630 }
1631
1632 /**
1633 * Returns the value obtained by rotating the two's complement binary
1634 * representation of the specified {@code int} value left by the
1635 * specified number of bits. (Bits shifted out of the left hand, or
1636 * high-order, side reenter on the right, or low-order.)
1637 *
1638 * <p>Note that left rotation with a negative distance is equivalent to
1639 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1640 * distance)}. Note also that rotation by any multiple of 32 is a
1641 * no-op, so all but the last five bits of the rotation distance can be
1642 * ignored, even if the distance is negative: {@code rotateLeft(val,
1643 * distance) == rotateLeft(val, distance & 0x1F)}.
1644 *
1645 * @param i the value whose bits are to be rotated left
1646 * @param distance the number of bit positions to rotate left
1647 * @return the value obtained by rotating the two's complement binary
1648 * representation of the specified {@code int} value left by the
1649 * specified number of bits.
1650 * @since 1.5
1651 */
1652 public static int rotateLeft(int i, int distance) {
1653 return (i << distance) | (i >>> -distance);
1654 }
1655
1656 /**
1657 * Returns the value obtained by rotating the two's complement binary
1658 * representation of the specified {@code int} value right by the
1659 * specified number of bits. (Bits shifted out of the right hand, or
1660 * low-order, side reenter on the left, or high-order.)
1661 *
1662 * <p>Note that right rotation with a negative distance is equivalent to
1663 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1664 * distance)}. Note also that rotation by any multiple of 32 is a
1665 * no-op, so all but the last five bits of the rotation distance can be
1666 * ignored, even if the distance is negative: {@code rotateRight(val,
1667 * distance) == rotateRight(val, distance & 0x1F)}.
1668 *
1669 * @param i the value whose bits are to be rotated right
1670 * @param distance the number of bit positions to rotate right
1671 * @return the value obtained by rotating the two's complement binary
1672 * representation of the specified {@code int} value right by the
1673 * specified number of bits.
1674 * @since 1.5
1675 */
1676 public static int rotateRight(int i, int distance) {
1677 return (i >>> distance) | (i << -distance);
1678 }
1679
1680 /**
1681 * Returns the value obtained by reversing the order of the bits in the
1682 * two's complement binary representation of the specified {@code int}
1683 * value.
1684 *
1685 * @param i the value to be reversed
1686 * @return the value obtained by reversing order of the bits in the
1687 * specified {@code int} value.
1688 * @since 1.5
1689 */
1690 @IntrinsicCandidate
1691 public static int reverse(int i) {
1692 // HD, Figure 7-1
1693 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1694 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1695 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1696
1697 return reverseBytes(i);
1698 }
1699
1700 /**
1701 * Returns the value obtained by compressing the bits of the
1702 * specified {@code int} value, {@code i}, in accordance with
1703 * the specified bit mask.
1704 * <p>
1705 * For each one-bit value {@code mb} of the mask, from least
1706 * significant to most significant, the bit value of {@code i} at
1707 * the same bit location as {@code mb} is assigned to the compressed
1708 * value contiguously starting from the least significant bit location.
1709 * All the upper remaining bits of the compressed value are set
1710 * to zero.
1711 *
1712 * @apiNote
1713 * Consider the simple case of compressing the digits of a hexadecimal
1714 * value:
1715 * {@snippet lang="java" :
1716 * // Compressing drink to food
1717 * compress(0xCAFEBABE, 0xFF00FFF0) == 0xCABAB
1718 * }
1719 * Starting from the least significant hexadecimal digit at position 0
1720 * from the right, the mask {@code 0xFF00FFF0} selects hexadecimal digits
1721 * at positions 1, 2, 3, 6 and 7 of {@code 0xCAFEBABE}. The selected digits
1722 * occur in the resulting compressed value contiguously from digit position
1723 * 0 in the same order.
1724 * <p>
1725 * The following identities all return {@code true} and are helpful to
1726 * understand the behaviour of {@code compress}:
1727 * {@snippet lang="java" :
1728 * // Returns 1 if the bit at position n is one
1729 * compress(x, 1 << n) == (x >> n & 1)
1730 *
1731 * // Logical shift right
1732 * compress(x, -1 << n) == x >>> n
1733 *
1734 * // Any bits not covered by the mask are ignored
1735 * compress(x, m) == compress(x & m, m)
1736 *
1737 * // Compressing a value by itself
1738 * compress(m, m) == (m == -1 || m == 0) ? m : (1 << bitCount(m)) - 1
1739 *
1740 * // Expanding then compressing with the same mask
1741 * compress(expand(x, m), m) == x & compress(m, m)
1742 * }
1743 * <p>
1744 * The Sheep And Goats (SAG) operation (see Hacker's Delight, Second Edition, section 7.7)
1745 * can be implemented as follows:
1746 * {@snippet lang="java" :
1747 * int compressLeft(int i, int mask) {
1748 * // This implementation follows the description in Hacker's Delight which
1749 * // is informative. A more optimal implementation is:
1750 * // Integer.compress(i, mask) << -Integer.bitCount(mask)
1751 * return Integer.reverse(
1752 * Integer.compress(Integer.reverse(i), Integer.reverse(mask)));
1753 * }
1754 *
1755 * int sag(int i, int mask) {
1756 * return compressLeft(i, mask) | Integer.compress(i, ~mask);
1757 * }
1758 *
1759 * // Separate the sheep from the goats
1760 * sag(0xCAFEBABE, 0xFF00FFF0) == 0xCABABFEE
1761 * }
1762 *
1763 * @param i the value whose bits are to be compressed
1764 * @param mask the bit mask
1765 * @return the compressed value
1766 * @see #expand
1767 * @since 19
1768 */
1769 @IntrinsicCandidate
1770 public static int compress(int i, int mask) {
1771 // See Hacker's Delight (2nd ed) section 7.4 Compress, or Generalized Extract
1772
1773 i = i & mask; // Clear irrelevant bits
1774 int maskCount = ~mask << 1; // Count 0's to right
1775
1776 for (int j = 0; j < 5; j++) {
1777 // Parallel prefix
1778 // Mask prefix identifies bits of the mask that have an odd number of 0's to the right
1779 int maskPrefix = parallelSuffix(maskCount);
1780 // Bits to move
1781 int maskMove = maskPrefix & mask;
1782 // Compress mask
1783 mask = (mask ^ maskMove) | (maskMove >>> (1 << j));
1784 // Bits of i to be moved
1785 int t = i & maskMove;
1786 // Compress i
1787 i = (i ^ t) | (t >>> (1 << j));
1788 // Adjust the mask count by identifying bits that have 0 to the right
1789 maskCount = maskCount & ~maskPrefix;
1790 }
1791 return i;
1792 }
1793
1794 /**
1795 * Returns the value obtained by expanding the bits of the
1796 * specified {@code int} value, {@code i}, in accordance with
1797 * the specified bit mask.
1798 * <p>
1799 * For each one-bit value {@code mb} of the mask, from least
1800 * significant to most significant, the next contiguous bit value
1801 * of {@code i} starting at the least significant bit is assigned
1802 * to the expanded value at the same bit location as {@code mb}.
1803 * All other remaining bits of the expanded value are set to zero.
1804 *
1805 * @apiNote
1806 * Consider the simple case of expanding the digits of a hexadecimal
1807 * value:
1808 * {@snippet lang="java" :
1809 * expand(0x0000CABAB, 0xFF00FFF0) == 0xCA00BAB0
1810 * }
1811 * Starting from the least significant hexadecimal digit at position 0
1812 * from the right, the mask {@code 0xFF00FFF0} selects the first five
1813 * hexadecimal digits of {@code 0x0000CABAB}. The selected digits occur
1814 * in the resulting expanded value in order at positions 1, 2, 3, 6, and 7.
1815 * <p>
1816 * The following identities all return {@code true} and are helpful to
1817 * understand the behaviour of {@code expand}:
1818 * {@snippet lang="java" :
1819 * // Logically shift right the bit at position 0
1820 * expand(x, 1 << n) == (x & 1) << n
1821 *
1822 * // Logically shift right
1823 * expand(x, -1 << n) == x << n
1824 *
1825 * // Expanding all bits returns the mask
1826 * expand(-1, m) == m
1827 *
1828 * // Any bits not covered by the mask are ignored
1829 * expand(x, m) == expand(x, m) & m
1830 *
1831 * // Compressing then expanding with the same mask
1832 * expand(compress(x, m), m) == x & m
1833 * }
1834 * <p>
1835 * The select operation for determining the position of the one-bit with
1836 * index {@code n} in a {@code int} value can be implemented as follows:
1837 * {@snippet lang="java" :
1838 * int select(int i, int n) {
1839 * // the one-bit in i (the mask) with index n
1840 * int nthBit = Integer.expand(1 << n, i);
1841 * // the bit position of the one-bit with index n
1842 * return Integer.numberOfTrailingZeros(nthBit);
1843 * }
1844 *
1845 * // The one-bit with index 0 is at bit position 1
1846 * select(0b10101010_10101010, 0) == 1
1847 * // The one-bit with index 3 is at bit position 7
1848 * select(0b10101010_10101010, 3) == 7
1849 * }
1850 *
1851 * @param i the value whose bits are to be expanded
1852 * @param mask the bit mask
1853 * @return the expanded value
1854 * @see #compress
1855 * @since 19
1856 */
1857 @IntrinsicCandidate
1858 public static int expand(int i, int mask) {
1859 // Save original mask
1860 int originalMask = mask;
1861 // Count 0's to right
1862 int maskCount = ~mask << 1;
1863 int maskPrefix = parallelSuffix(maskCount);
1864 // Bits to move
1865 int maskMove1 = maskPrefix & mask;
1866 // Compress mask
1867 mask = (mask ^ maskMove1) | (maskMove1 >>> (1 << 0));
1868 maskCount = maskCount & ~maskPrefix;
1869
1870 maskPrefix = parallelSuffix(maskCount);
1871 // Bits to move
1872 int maskMove2 = maskPrefix & mask;
1873 // Compress mask
1874 mask = (mask ^ maskMove2) | (maskMove2 >>> (1 << 1));
1875 maskCount = maskCount & ~maskPrefix;
1876
1877 maskPrefix = parallelSuffix(maskCount);
1878 // Bits to move
1879 int maskMove3 = maskPrefix & mask;
1880 // Compress mask
1881 mask = (mask ^ maskMove3) | (maskMove3 >>> (1 << 2));
1882 maskCount = maskCount & ~maskPrefix;
1883
1884 maskPrefix = parallelSuffix(maskCount);
1885 // Bits to move
1886 int maskMove4 = maskPrefix & mask;
1887 // Compress mask
1888 mask = (mask ^ maskMove4) | (maskMove4 >>> (1 << 3));
1889 maskCount = maskCount & ~maskPrefix;
1890
1891 maskPrefix = parallelSuffix(maskCount);
1892 // Bits to move
1893 int maskMove5 = maskPrefix & mask;
1894
1895 int t = i << (1 << 4);
1896 i = (i & ~maskMove5) | (t & maskMove5);
1897 t = i << (1 << 3);
1898 i = (i & ~maskMove4) | (t & maskMove4);
1899 t = i << (1 << 2);
1900 i = (i & ~maskMove3) | (t & maskMove3);
1901 t = i << (1 << 1);
1902 i = (i & ~maskMove2) | (t & maskMove2);
1903 t = i << (1 << 0);
1904 i = (i & ~maskMove1) | (t & maskMove1);
1905
1906 // Clear irrelevant bits
1907 return i & originalMask;
1908 }
1909
1910 @ForceInline
1911 private static int parallelSuffix(int maskCount) {
1912 int maskPrefix = maskCount ^ (maskCount << 1);
1913 maskPrefix = maskPrefix ^ (maskPrefix << 2);
1914 maskPrefix = maskPrefix ^ (maskPrefix << 4);
1915 maskPrefix = maskPrefix ^ (maskPrefix << 8);
1916 maskPrefix = maskPrefix ^ (maskPrefix << 16);
1917 return maskPrefix;
1918 }
1919
1920 /**
1921 * Returns the signum function of the specified {@code int} value. (The
1922 * return value is -1 if the specified value is negative; 0 if the
1923 * specified value is zero; and 1 if the specified value is positive.)
1924 *
1925 * @param i the value whose signum is to be computed
1926 * @return the signum function of the specified {@code int} value.
1927 * @since 1.5
1928 */
1929 public static int signum(int i) {
1930 // HD, Section 2-7
1931 return (i >> 31) | (-i >>> 31);
1932 }
1933
1934 /**
1935 * Returns the value obtained by reversing the order of the bytes in the
1936 * two's complement representation of the specified {@code int} value.
1937 *
1938 * @param i the value whose bytes are to be reversed
1939 * @return the value obtained by reversing the bytes in the specified
1940 * {@code int} value.
1941 * @since 1.5
1942 */
1943 @IntrinsicCandidate
1944 public static int reverseBytes(int i) {
1945 return (i << 24) |
1946 ((i & 0xff00) << 8) |
1947 ((i >>> 8) & 0xff00) |
1948 (i >>> 24);
1949 }
1950
1951 /**
1952 * Adds two integers together as per the + operator.
1953 *
1954 * @param a the first operand
1955 * @param b the second operand
1956 * @return the sum of {@code a} and {@code b}
1957 * @see java.util.function.BinaryOperator
1958 * @since 1.8
1959 */
1960 public static int sum(int a, int b) {
1961 return a + b;
1962 }
1963
1964 /**
1965 * Returns the greater of two {@code int} values
1966 * as if by calling {@link Math#max(int, int) Math.max}.
1967 *
1968 * @param a the first operand
1969 * @param b the second operand
1970 * @return the greater of {@code a} and {@code b}
1971 * @see java.util.function.BinaryOperator
1972 * @since 1.8
1973 */
1974 public static int max(int a, int b) {
1975 return Math.max(a, b);
1976 }
1977
1978 /**
1979 * Returns the smaller of two {@code int} values
1980 * as if by calling {@link Math#min(int, int) Math.min}.
1981 *
1982 * @param a the first operand
1983 * @param b the second operand
1984 * @return the smaller of {@code a} and {@code b}
1985 * @see java.util.function.BinaryOperator
1986 * @since 1.8
1987 */
1988 public static int min(int a, int b) {
1989 return Math.min(a, b);
1990 }
1991
1992 /**
1993 * Returns an {@link Optional} containing the nominal descriptor for this
1994 * instance, which is the instance itself.
1995 *
1996 * @return an {@link Optional} describing the {@linkplain Integer} instance
1997 * @since 12
1998 */
1999 @Override
2000 public Optional<Integer> describeConstable() {
2001 return Optional.of(this);
2002 }
2003
2004 /**
2005 * Resolves this instance as a {@link ConstantDesc}, the result of which is
2006 * the instance itself.
2007 *
2008 * @param lookup ignored
2009 * @return the {@linkplain Integer} instance
2010 * @since 12
2011 */
2012 @Override
2013 public Integer resolveConstantDesc(MethodHandles.Lookup lookup) {
2014 return this;
2015 }
2016
2017 /** use serialVersionUID from JDK 1.0.2 for interoperability */
2018 @java.io.Serial
2019 @Native private static final long serialVersionUID = 1360826667806852920L;
2020 }