1 /*
  2  * Copyright (c) 1996, 2023, 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.vm.annotation.IntrinsicCandidate;
 30 import jdk.internal.vm.annotation.Stable;
 31 
 32 import java.lang.constant.Constable;
 33 import java.lang.constant.DynamicConstantDesc;
 34 import java.util.Optional;
 35 
 36 import static java.lang.constant.ConstantDescs.BSM_EXPLICIT_CAST;
 37 import static java.lang.constant.ConstantDescs.CD_byte;
 38 import static java.lang.constant.ConstantDescs.CD_int;
 39 import static java.lang.constant.ConstantDescs.DEFAULT_NAME;
 40 
 41 /**
 42  *
 43  * The {@code Byte} class wraps a value of primitive type {@code byte}
 44  * in an object.  An object of type {@code Byte} contains a single
 45  * field whose type is {@code byte}.
 46  *
 47  * <p>In addition, this class provides several methods for converting
 48  * a {@code byte} to a {@code String} and a {@code String} to a {@code
 49  * byte}, as well as other constants and methods useful when dealing
 50  * with a {@code byte}.
 51  *
 52  * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
 53  * class; programmers should treat instances that are
 54  * {@linkplain #equals(Object) equal} as interchangeable and should not
 55  * use instances for synchronization, or unpredictable behavior may
 56  * occur. For example, in a future release, synchronization may fail.
 57  *
 58  * @author  Nakul Saraiya
 59  * @author  Joseph D. Darcy
 60  * @see     java.lang.Number
 61  * @since   1.1
 62  */
 63 @jdk.internal.ValueBased
 64 public final class Byte extends Number implements Comparable<Byte>, Constable {
 65 
 66     /**
 67      * A constant holding the minimum value a {@code byte} can
 68      * have, -2<sup>7</sup>.
 69      */
 70     public static final byte   MIN_VALUE = -128;
 71 
 72     /**
 73      * A constant holding the maximum value a {@code byte} can
 74      * have, 2<sup>7</sup>-1.
 75      */
 76     public static final byte   MAX_VALUE = 127;
 77 
 78     /**
 79      * The {@code Class} instance representing the primitive type
 80      * {@code byte}.
 81      */
 82     @SuppressWarnings("unchecked")
 83     public static final Class<Byte>     TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
 84 
 85     /**
 86      * Returns a new {@code String} object representing the
 87      * specified {@code byte}. The radix is assumed to be 10.
 88      *
 89      * @param b the {@code byte} to be converted
 90      * @return the string representation of the specified {@code byte}
 91      * @see java.lang.Integer#toString(int)
 92      */
 93     public static String toString(byte b) {
 94         return Integer.toString(b);
 95     }
 96 
 97     /**
 98      * Returns an {@link Optional} containing the nominal descriptor for this
 99      * instance.
100      *
101      * @return an {@link Optional} describing the {@linkplain Byte} instance
102      * @since 15
103      */
104     @Override
105     public Optional<DynamicConstantDesc<Byte>> describeConstable() {
106         return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
107     }
108 
109     private static final class ByteCache {
110         private ByteCache() {}
111 
112         @Stable
113         static final Byte[] cache;
114         static Byte[] archivedCache;
115 
116         static {
117             final int size = -(-128) + 127 + 1;
118 
119             // Load and use the archived cache if it exists
120             CDS.initializeFromArchive(ByteCache.class);
121             if (archivedCache == null || archivedCache.length != size) {
122                 Byte[] c = new Byte[size];
123                 byte value = (byte)-128;
124                 for(int i = 0; i < size; i++) {
125                     c[i] = new Byte(value++);
126                 }
127                 archivedCache = c;
128             }
129             cache = archivedCache;
130         }
131     }
132 
133     /**
134      * Returns a {@code Byte} instance representing the specified
135      * {@code byte} value.
136      * If a new {@code Byte} instance is not required, this method
137      * should generally be used in preference to the constructor
138      * {@link #Byte(byte)}, as this method is likely to yield
139      * significantly better space and time performance since
140      * all byte values are cached.
141      *
142      * @param  b a byte value.
143      * @return a {@code Byte} instance representing {@code b}.
144      * @since  1.5
145      */
146     @IntrinsicCandidate
147     public static Byte valueOf(byte b) {
148         final int offset = 128;
149         return ByteCache.cache[(int)b + offset];
150     }
151 
152     /**
153      * Parses the string argument as a signed {@code byte} in the
154      * radix specified by the second argument. The characters in the
155      * string must all be digits, of the specified radix (as
156      * determined by whether {@link java.lang.Character#digit(char,
157      * int)} returns a nonnegative value) except that the first
158      * character may be an ASCII minus sign {@code '-'}
159      * ({@code '\u005Cu002D'}) to indicate a negative value or an
160      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
161      * indicate a positive value.  The resulting {@code byte} value is
162      * returned.
163      *
164      * <p>An exception of type {@code NumberFormatException} is
165      * thrown if any of the following situations occurs:
166      * <ul>
167      * <li> The first argument is {@code null} or is a string of
168      * length zero.
169      *
170      * <li> The radix is either smaller than {@link
171      * java.lang.Character#MIN_RADIX} or larger than {@link
172      * java.lang.Character#MAX_RADIX}.
173      *
174      * <li> Any character of the string is not a digit of the
175      * specified radix, except that the first character may be a minus
176      * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
177      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
178      * string is longer than length 1.
179      *
180      * <li> The value represented by the string is not a value of type
181      * {@code byte}.
182      * </ul>
183      *
184      * @param s         the {@code String} containing the
185      *                  {@code byte}
186      *                  representation to be parsed
187      * @param radix     the radix to be used while parsing {@code s}
188      * @return          the {@code byte} value represented by the string
189      *                   argument in the specified radix
190      * @throws          NumberFormatException If the string does
191      *                  not contain a parsable {@code byte}.
192      */
193     public static byte parseByte(String s, int radix)
194         throws NumberFormatException {
195         int i = Integer.parseInt(s, radix);
196         if (i < MIN_VALUE || i > MAX_VALUE)
197             throw new NumberFormatException(
198                 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
199         return (byte)i;
200     }
201 
202     /**
203      * Parses the string argument as a signed decimal {@code
204      * byte}. The characters in the string must all be decimal digits,
205      * except that the first character may be an ASCII minus sign
206      * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
207      * value or an ASCII plus sign {@code '+'}
208      * ({@code '\u005Cu002B'}) to indicate a positive value. The
209      * resulting {@code byte} value is returned, exactly as if the
210      * argument and the radix 10 were given as arguments to the {@link
211      * #parseByte(java.lang.String, int)} method.
212      *
213      * @param s         a {@code String} containing the
214      *                  {@code byte} representation to be parsed
215      * @return          the {@code byte} value represented by the
216      *                  argument in decimal
217      * @throws          NumberFormatException if the string does not
218      *                  contain a parsable {@code byte}.
219      */
220     public static byte parseByte(String s) throws NumberFormatException {
221         return parseByte(s, 10);
222     }
223 
224     /**
225      * Returns a {@code Byte} object holding the value
226      * extracted from the specified {@code String} when parsed
227      * with the radix given by the second argument. The first argument
228      * is interpreted as representing a signed {@code byte} in
229      * the radix specified by the second argument, exactly as if the
230      * argument were given to the {@link #parseByte(java.lang.String,
231      * int)} method. The result is a {@code Byte} object that
232      * represents the {@code byte} value specified by the string.
233      *
234      * <p> In other words, this method returns a {@code Byte} object
235      * equal to the value of:
236      *
237      * <blockquote>
238      * {@code Byte.valueOf(Byte.parseByte(s, radix))}
239      * </blockquote>
240      *
241      * @param s         the string to be parsed
242      * @param radix     the radix to be used in interpreting {@code s}
243      * @return          a {@code Byte} object holding the value
244      *                  represented by the string argument in the
245      *                  specified radix.
246      * @throws          NumberFormatException If the {@code String} does
247      *                  not contain a parsable {@code byte}.
248      */
249     public static Byte valueOf(String s, int radix)
250         throws NumberFormatException {
251         return valueOf(parseByte(s, radix));
252     }
253 
254     /**
255      * Returns a {@code Byte} object holding the value
256      * given by the specified {@code String}. The argument is
257      * interpreted as representing a signed decimal {@code byte},
258      * exactly as if the argument were given to the {@link
259      * #parseByte(java.lang.String)} method. The result is a
260      * {@code Byte} object that represents the {@code byte}
261      * value specified by the string.
262      *
263      * <p> In other words, this method returns a {@code Byte} object
264      * equal to the value of:
265      *
266      * <blockquote>
267      * {@code Byte.valueOf(Byte.parseByte(s))}
268      * </blockquote>
269      *
270      * @param s         the string to be parsed
271      * @return          a {@code Byte} object holding the value
272      *                  represented by the string argument
273      * @throws          NumberFormatException If the {@code String} does
274      *                  not contain a parsable {@code byte}.
275      */
276     public static Byte valueOf(String s) throws NumberFormatException {
277         return valueOf(s, 10);
278     }
279 
280     /**
281      * Decodes a {@code String} into a {@code Byte}.
282      * Accepts decimal, hexadecimal, and octal numbers given by
283      * the following grammar:
284      *
285      * <blockquote>
286      * <dl>
287      * <dt><i>DecodableString:</i>
288      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
289      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
290      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
291      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
292      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
293      *
294      * <dt><i>Sign:</i>
295      * <dd>{@code -}
296      * <dd>{@code +}
297      * </dl>
298      * </blockquote>
299      *
300      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
301      * are as defined in section {@jls 3.10.1} of
302      * <cite>The Java Language Specification</cite>,
303      * except that underscores are not accepted between digits.
304      *
305      * <p>The sequence of characters following an optional
306      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
307      * "{@code #}", or leading zero) is parsed as by the {@code
308      * Byte.parseByte} method with the indicated radix (10, 16, or 8).
309      * This sequence of characters must represent a positive value or
310      * a {@link NumberFormatException} will be thrown.  The result is
311      * negated if first character of the specified {@code String} is
312      * the minus sign.  No whitespace characters are permitted in the
313      * {@code String}.
314      *
315      * @param     nm the {@code String} to decode.
316      * @return   a {@code Byte} object holding the {@code byte}
317      *          value represented by {@code nm}
318      * @throws  NumberFormatException  if the {@code String} does not
319      *            contain a parsable {@code byte}.
320      * @see java.lang.Byte#parseByte(java.lang.String, int)
321      */
322     public static Byte decode(String nm) throws NumberFormatException {
323         int i = Integer.decode(nm);
324         if (i < MIN_VALUE || i > MAX_VALUE)
325             throw new NumberFormatException(
326                     "Value " + i + " out of range from input " + nm);
327         return valueOf((byte)i);
328     }
329 
330     /**
331      * The value of the {@code Byte}.
332      *
333      * @serial
334      */
335     private final byte value;
336 
337     /**
338      * Constructs a newly allocated {@code Byte} object that
339      * represents the specified {@code byte} value.
340      *
341      * @param value     the value to be represented by the
342      *                  {@code Byte}.
343      *
344      * @deprecated
345      * It is rarely appropriate to use this constructor. The static factory
346      * {@link #valueOf(byte)} is generally a better choice, as it is
347      * likely to yield significantly better space and time performance.
348      */
349     @Deprecated(since="9", forRemoval = true)
350     public Byte(byte value) {
351         this.value = value;
352     }
353 
354     /**
355      * Constructs a newly allocated {@code Byte} object that
356      * represents the {@code byte} value indicated by the
357      * {@code String} parameter. The string is converted to a
358      * {@code byte} value in exactly the manner used by the
359      * {@code parseByte} method for radix 10.
360      *
361      * @param s         the {@code String} to be converted to a
362      *                  {@code Byte}
363      * @throws          NumberFormatException if the {@code String}
364      *                  does not contain a parsable {@code byte}.
365      *
366      * @deprecated
367      * It is rarely appropriate to use this constructor.
368      * Use {@link #parseByte(String)} to convert a string to a
369      * {@code byte} primitive, or use {@link #valueOf(String)}
370      * to convert a string to a {@code Byte} object.
371      */
372     @Deprecated(since="9", forRemoval = true)
373     public Byte(String s) throws NumberFormatException {
374         this.value = parseByte(s, 10);
375     }
376 
377     /**
378      * Returns the value of this {@code Byte} as a
379      * {@code byte}.
380      */
381     @IntrinsicCandidate
382     public byte byteValue() {
383         return value;
384     }
385 
386     /**
387      * Returns the value of this {@code Byte} as a {@code short} after
388      * a widening primitive conversion.
389      * @jls 5.1.2 Widening Primitive Conversion
390      */
391     public short shortValue() {
392         return (short)value;
393     }
394 
395     /**
396      * Returns the value of this {@code Byte} as an {@code int} after
397      * a widening primitive conversion.
398      * @jls 5.1.2 Widening Primitive Conversion
399      */
400     public int intValue() {
401         return (int)value;
402     }
403 
404     /**
405      * Returns the value of this {@code Byte} as a {@code long} after
406      * a widening primitive conversion.
407      * @jls 5.1.2 Widening Primitive Conversion
408      */
409     public long longValue() {
410         return (long)value;
411     }
412 
413     /**
414      * Returns the value of this {@code Byte} as a {@code float} after
415      * a widening primitive conversion.
416      * @jls 5.1.2 Widening Primitive Conversion
417      */
418     public float floatValue() {
419         return (float)value;
420     }
421 
422     /**
423      * Returns the value of this {@code Byte} as a {@code double}
424      * after a widening primitive conversion.
425      * @jls 5.1.2 Widening Primitive Conversion
426      */
427     public double doubleValue() {
428         return (double)value;
429     }
430 
431     /**
432      * Returns a {@code String} object representing this
433      * {@code Byte}'s value.  The value is converted to signed
434      * decimal representation and returned as a string, exactly as if
435      * the {@code byte} value were given as an argument to the
436      * {@link java.lang.Byte#toString(byte)} method.
437      *
438      * @return  a string representation of the value of this object in
439      *          base&nbsp;10.
440      */
441     @Override
442     public String toString() {
443         return Integer.toString(value);
444     }
445 
446     /**
447      * Returns a hash code for this {@code Byte}; equal to the result
448      * of invoking {@code intValue()}.
449      *
450      * @return a hash code value for this {@code Byte}
451      */
452     @Override
453     public int hashCode() {
454         return Byte.hashCode(value);
455     }
456 
457     /**
458      * Returns a hash code for a {@code byte} value; compatible with
459      * {@code Byte.hashCode()}.
460      *
461      * @param value the value to hash
462      * @return a hash code value for a {@code byte} value.
463      * @since 1.8
464      */
465     public static int hashCode(byte value) {
466         return (int)value;
467     }
468 
469     /**
470      * Compares this object to the specified object.  The result is
471      * {@code true} if and only if the argument is not
472      * {@code null} and is a {@code Byte} object that
473      * contains the same {@code byte} value as this object.
474      *
475      * @param obj       the object to compare with
476      * @return          {@code true} if the objects are the same;
477      *                  {@code false} otherwise.
478      */
479     public boolean equals(Object obj) {
480         if (obj instanceof Byte) {
481             return value == ((Byte)obj).byteValue();
482         }
483         return false;
484     }
485 
486     /**
487      * Compares two {@code Byte} objects numerically.
488      *
489      * @param   anotherByte   the {@code Byte} to be compared.
490      * @return  the value {@code 0} if this {@code Byte} is
491      *          equal to the argument {@code Byte}; a value less than
492      *          {@code 0} if this {@code Byte} is numerically less
493      *          than the argument {@code Byte}; and a value greater than
494      *           {@code 0} if this {@code Byte} is numerically
495      *           greater than the argument {@code Byte} (signed
496      *           comparison).
497      * @since   1.2
498      */
499     public int compareTo(Byte anotherByte) {
500         return compare(this.value, anotherByte.value);
501     }
502 
503     /**
504      * Compares two {@code byte} values numerically.
505      * The value returned is identical to what would be returned by:
506      * <pre>
507      *    Byte.valueOf(x).compareTo(Byte.valueOf(y))
508      * </pre>
509      *
510      * @param  x the first {@code byte} to compare
511      * @param  y the second {@code byte} to compare
512      * @return the value {@code 0} if {@code x == y};
513      *         a value less than {@code 0} if {@code x < y}; and
514      *         a value greater than {@code 0} if {@code x > y}
515      * @since 1.7
516      */
517     public static int compare(byte x, byte y) {
518         return x - y;
519     }
520 
521     /**
522      * Compares two {@code byte} values numerically treating the values
523      * as unsigned.
524      *
525      * @param  x the first {@code byte} to compare
526      * @param  y the second {@code byte} to compare
527      * @return the value {@code 0} if {@code x == y}; a value less
528      *         than {@code 0} if {@code x < y} as unsigned values; and
529      *         a value greater than {@code 0} if {@code x > y} as
530      *         unsigned values
531      * @since 9
532      */
533     public static int compareUnsigned(byte x, byte y) {
534         return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y);
535     }
536 
537     /**
538      * Converts the argument to an {@code int} by an unsigned
539      * conversion.  In an unsigned conversion to an {@code int}, the
540      * high-order 24 bits of the {@code int} are zero and the
541      * low-order 8 bits are equal to the bits of the {@code byte} argument.
542      *
543      * Consequently, zero and positive {@code byte} values are mapped
544      * to a numerically equal {@code int} value and negative {@code
545      * byte} values are mapped to an {@code int} value equal to the
546      * input plus 2<sup>8</sup>.
547      *
548      * @param  x the value to convert to an unsigned {@code int}
549      * @return the argument converted to {@code int} by an unsigned
550      *         conversion
551      * @since 1.8
552      */
553     public static int toUnsignedInt(byte x) {
554         return ((int) x) & 0xff;
555     }
556 
557     /**
558      * Converts the argument to a {@code long} by an unsigned
559      * conversion.  In an unsigned conversion to a {@code long}, the
560      * high-order 56 bits of the {@code long} are zero and the
561      * low-order 8 bits are equal to the bits of the {@code byte} argument.
562      *
563      * Consequently, zero and positive {@code byte} values are mapped
564      * to a numerically equal {@code long} value and negative {@code
565      * byte} values are mapped to a {@code long} value equal to the
566      * input plus 2<sup>8</sup>.
567      *
568      * @param  x the value to convert to an unsigned {@code long}
569      * @return the argument converted to {@code long} by an unsigned
570      *         conversion
571      * @since 1.8
572      */
573     public static long toUnsignedLong(byte x) {
574         return ((long) x) & 0xffL;
575     }
576 
577 
578     /**
579      * The number of bits used to represent a {@code byte} value in two's
580      * complement binary form.
581      *
582      * @since 1.5
583      */
584     public static final int SIZE = 8;
585 
586     /**
587      * The number of bytes used to represent a {@code byte} value in two's
588      * complement binary form.
589      *
590      * @since 1.8
591      */
592     public static final int BYTES = SIZE / Byte.SIZE;
593 
594     /** use serialVersionUID from JDK 1.1. for interoperability */
595     @java.io.Serial
596     private static final long serialVersionUID = -7183698231559129828L;
597 }