1 /*
2 * Copyright (c) 1996, 2025, 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.AOTSafeClassInitializer;
30 import jdk.internal.vm.annotation.IntrinsicCandidate;
31 import jdk.internal.vm.annotation.Stable;
32
33 import java.lang.constant.Constable;
34 import java.lang.constant.DynamicConstantDesc;
35 import java.util.Optional;
36
37 import static java.lang.constant.ConstantDescs.BSM_EXPLICIT_CAST;
38 import static java.lang.constant.ConstantDescs.CD_byte;
39 import static java.lang.constant.ConstantDescs.DEFAULT_NAME;
40
41 /**
42 * The {@code Byte} class is the {@linkplain
43 * java.lang##wrapperClass wrapper class} for values of the primitive
44 * type {@code byte}. An object of type {@code Byte} contains a
45 * single 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 * @see java.lang.Number
59 * @since 1.1
60 */
61 @jdk.internal.ValueBased
62 public final class Byte extends Number implements Comparable<Byte>, Constable {
63
64 /**
65 * A constant holding the minimum value a {@code byte} can
66 * have, -2<sup>7</sup>.
67 */
68 public static final byte MIN_VALUE = -128;
69
70 /**
71 * A constant holding the maximum value a {@code byte} can
72 * have, 2<sup>7</sup>-1.
73 */
74 public static final byte MAX_VALUE = 127;
75
76 /**
77 * The {@code Class} instance representing the primitive type
78 * {@code byte}.
79 */
80 public static final Class<Byte> TYPE = Class.getPrimitiveClass("byte");
81
82 /**
83 * Returns a new {@code String} object representing the
84 * specified {@code byte}. The radix is assumed to be 10.
85 *
86 * @param b the {@code byte} to be converted
87 * @return the string representation of the specified {@code byte}
88 * @see java.lang.Integer#toString(int)
89 */
90 public static String toString(byte b) {
91 return Integer.toString(b);
92 }
93
94 /**
95 * Returns an {@link Optional} containing the nominal descriptor for this
96 * instance.
97 *
98 * @return an {@link Optional} describing the {@linkplain Byte} instance
99 * @since 15
100 */
101 @Override
102 public Optional<DynamicConstantDesc<Byte>> describeConstable() {
103 return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
104 }
105
106 @AOTSafeClassInitializer
107 private static final class ByteCache {
108 private ByteCache() {}
109
110 @Stable
111 static final Byte[] cache;
112 static Byte[] archivedCache;
113
114 static {
115 final int size = -(-128) + 127 + 1;
116
117 // Load and use the archived cache if it exists
118 CDS.initializeFromArchive(ByteCache.class);
119 if (archivedCache == null) {
120 Byte[] c = new Byte[size];
121 byte value = (byte)-128;
122 for(int i = 0; i < size; i++) {
123 c[i] = new Byte(value++);
124 }
125 archivedCache = c;
126 }
127 cache = archivedCache;
128 assert cache.length == size;
129 }
130 }
131
132 /**
133 * Returns a {@code Byte} instance representing the specified
134 * {@code byte} value.
135 * If a new {@code Byte} instance is not required, this method
136 * should generally be used in preference to the constructor
137 * {@link #Byte(byte)}, as this method is likely to yield
138 * significantly better space and time performance since
139 * all byte values are cached.
140 *
141 * @param b a byte value.
142 * @return a {@code Byte} instance representing {@code b}.
143 * @since 1.5
144 */
145 @IntrinsicCandidate
146 public static Byte valueOf(byte b) {
147 final int offset = 128;
148 return ByteCache.cache[(int)b + offset];
149 }
150
151 /**
152 * Parses the string argument as a signed {@code byte} in the
153 * radix specified by the second argument. The characters in the
154 * string must all be digits, of the specified radix (as
155 * determined by whether {@link java.lang.Character#digit(char,
156 * int)} returns a nonnegative value) except that the first
157 * character may be an ASCII minus sign {@code '-'}
158 * ({@code '\u005Cu002D'}) to indicate a negative value or an
159 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
160 * indicate a positive value. The resulting {@code byte} value is
161 * returned.
162 *
163 * <p>An exception of type {@code NumberFormatException} is
164 * thrown if any of the following situations occurs:
165 * <ul>
166 * <li> The first argument is {@code null} or is a string of
167 * length zero.
168 *
169 * <li> The radix is either smaller than {@link
170 * java.lang.Character#MIN_RADIX} or larger than {@link
171 * java.lang.Character#MAX_RADIX}.
172 *
173 * <li> Any character of the string is not a digit of the
174 * specified radix, except that the first character may be a minus
175 * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
176 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
177 * string is longer than length 1.
178 *
179 * <li> The value represented by the string is not a value of type
180 * {@code byte}.
181 * </ul>
182 *
183 * @param s the {@code String} containing the
184 * {@code byte}
185 * representation to be parsed
186 * @param radix the radix to be used while parsing {@code s}
187 * @return the {@code byte} value represented by the string
188 * argument in the specified radix
189 * @throws NumberFormatException If the string does
190 * not contain a parsable {@code byte}.
191 */
192 public static byte parseByte(String s, int radix)
193 throws NumberFormatException {
194 int i = Integer.parseInt(s, radix);
195 if (i < MIN_VALUE || i > MAX_VALUE)
196 throw new NumberFormatException(
197 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
198 return (byte)i;
199 }
200
201 /**
202 * Parses the string argument as a signed decimal {@code
203 * byte}. The characters in the string must all be decimal digits,
204 * except that the first character may be an ASCII minus sign
205 * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
206 * value or an ASCII plus sign {@code '+'}
207 * ({@code '\u005Cu002B'}) to indicate a positive value. The
208 * resulting {@code byte} value is returned, exactly as if the
209 * argument and the radix 10 were given as arguments to the {@link
210 * #parseByte(java.lang.String, int)} method.
211 *
212 * @param s a {@code String} containing the
213 * {@code byte} representation to be parsed
214 * @return the {@code byte} value represented by the
215 * argument in decimal
216 * @throws NumberFormatException if the string does not
217 * contain a parsable {@code byte}.
218 */
219 public static byte parseByte(String s) throws NumberFormatException {
220 return parseByte(s, 10);
221 }
222
223 /**
224 * Returns a {@code Byte} object holding the value
225 * extracted from the specified {@code String} when parsed
226 * with the radix given by the second argument. The first argument
227 * is interpreted as representing a signed {@code byte} in
228 * the radix specified by the second argument, exactly as if the
229 * argument were given to the {@link #parseByte(java.lang.String,
230 * int)} method. The result is a {@code Byte} object that
231 * represents the {@code byte} value specified by the string.
232 *
233 * <p> In other words, this method returns a {@code Byte} object
234 * equal to the value of:
235 *
236 * <blockquote>
237 * {@code Byte.valueOf(Byte.parseByte(s, radix))}
238 * </blockquote>
239 *
240 * @param s the string to be parsed
241 * @param radix the radix to be used in interpreting {@code s}
242 * @return a {@code Byte} object holding the value
243 * represented by the string argument in the
244 * specified radix.
245 * @throws NumberFormatException If the {@code String} does
246 * not contain a parsable {@code byte}.
247 */
248 public static Byte valueOf(String s, int radix)
249 throws NumberFormatException {
250 return valueOf(parseByte(s, radix));
251 }
252
253 /**
254 * Returns a {@code Byte} object holding the value
255 * given by the specified {@code String}. The argument is
256 * interpreted as representing a signed decimal {@code byte},
257 * exactly as if the argument were given to the {@link
258 * #parseByte(java.lang.String)} method. The result is a
259 * {@code Byte} object that represents the {@code byte}
260 * value specified by the string.
261 *
262 * <p> In other words, this method returns a {@code Byte} object
263 * equal to the value of:
264 *
265 * <blockquote>
266 * {@code Byte.valueOf(Byte.parseByte(s))}
267 * </blockquote>
268 *
269 * @param s the string to be parsed
270 * @return a {@code Byte} object holding the value
271 * represented by the string argument
272 * @throws NumberFormatException If the {@code String} does
273 * not contain a parsable {@code byte}.
274 */
275 public static Byte valueOf(String s) throws NumberFormatException {
276 return valueOf(s, 10);
277 }
278
279 /**
280 * Decodes a {@code String} into a {@code Byte}.
281 * Accepts decimal, hexadecimal, and octal numbers given by
282 * the following grammar:
283 *
284 * <blockquote>
285 * <dl>
286 * <dt><i>DecodableString:</i>
287 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
288 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
289 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
290 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
291 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
292 *
293 * <dt><i>Sign:</i>
294 * <dd>{@code -}
295 * <dd>{@code +}
296 * </dl>
297 * </blockquote>
298 *
299 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
300 * are as defined in section {@jls 3.10.1} of
301 * <cite>The Java Language Specification</cite>,
302 * except that underscores are not accepted between digits.
303 *
304 * <p>The sequence of characters following an optional
305 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
306 * "{@code #}", or leading zero) is parsed as by the {@code
307 * Byte.parseByte} method with the indicated radix (10, 16, or 8).
308 * This sequence of characters must represent a positive value or
309 * a {@link NumberFormatException} will be thrown. The result is
310 * negated if first character of the specified {@code String} is
311 * the minus sign. No whitespace characters are permitted in the
312 * {@code String}.
313 *
314 * @param nm the {@code String} to decode.
315 * @return a {@code Byte} object holding the {@code byte}
316 * value represented by {@code nm}
317 * @throws NumberFormatException if the {@code String} does not
318 * contain a parsable {@code byte}.
319 * @see java.lang.Byte#parseByte(java.lang.String, int)
320 */
321 public static Byte decode(String nm) throws NumberFormatException {
322 int i = Integer.decode(nm);
323 if (i < MIN_VALUE || i > MAX_VALUE)
324 throw new NumberFormatException(
325 "Value " + i + " out of range from input " + nm);
326 return valueOf((byte)i);
327 }
328
329 /**
330 * The value of the {@code Byte}.
331 *
332 * @serial
333 */
334 private final byte value;
335
336 /**
337 * Constructs a newly allocated {@code Byte} object that
338 * represents the specified {@code byte} value.
339 *
340 * @param value the value to be represented by the
341 * {@code Byte}.
342 *
343 * @deprecated
344 * It is rarely appropriate to use this constructor. The static factory
345 * {@link #valueOf(byte)} is generally a better choice, as it is
346 * likely to yield significantly better space and time performance.
347 */
348 @Deprecated(since="9")
349 public Byte(byte value) {
350 this.value = value;
351 }
352
353 /**
354 * Constructs a newly allocated {@code Byte} object that
355 * represents the {@code byte} value indicated by the
356 * {@code String} parameter. The string is converted to a
357 * {@code byte} value in exactly the manner used by the
358 * {@code parseByte} method for radix 10.
359 *
360 * @param s the {@code String} to be converted to a
361 * {@code Byte}
362 * @throws NumberFormatException if the {@code String}
363 * does not contain a parsable {@code byte}.
364 *
365 * @deprecated
366 * It is rarely appropriate to use this constructor.
367 * Use {@link #parseByte(String)} to convert a string to a
368 * {@code byte} primitive, or use {@link #valueOf(String)}
369 * to convert a string to a {@code Byte} object.
370 */
371 @Deprecated(since="9")
372 public Byte(String s) throws NumberFormatException {
373 this.value = parseByte(s, 10);
374 }
375
376 /**
377 * Returns the value of this {@code Byte} as a
378 * {@code byte}.
379 */
380 @IntrinsicCandidate
381 public byte byteValue() {
382 return value;
383 }
384
385 /**
386 * Returns the value of this {@code Byte} as a {@code short} after
387 * a widening primitive conversion.
388 * @jls 5.1.2 Widening Primitive Conversion
389 */
390 public short shortValue() {
391 return (short)value;
392 }
393
394 /**
395 * Returns the value of this {@code Byte} as an {@code int} after
396 * a widening primitive conversion.
397 * @jls 5.1.2 Widening Primitive Conversion
398 */
399 public int intValue() {
400 return (int)value;
401 }
402
403 /**
404 * Returns the value of this {@code Byte} as a {@code long} after
405 * a widening primitive conversion.
406 * @jls 5.1.2 Widening Primitive Conversion
407 */
408 public long longValue() {
409 return (long)value;
410 }
411
412 /**
413 * Returns the value of this {@code Byte} as a {@code float} after
414 * a widening primitive conversion.
415 * @jls 5.1.2 Widening Primitive Conversion
416 */
417 public float floatValue() {
418 return (float)value;
419 }
420
421 /**
422 * Returns the value of this {@code Byte} as a {@code double}
423 * after a widening primitive conversion.
424 * @jls 5.1.2 Widening Primitive Conversion
425 */
426 public double doubleValue() {
427 return (double)value;
428 }
429
430 /**
431 * Returns a {@code String} object representing this
432 * {@code Byte}'s value. The value is converted to signed
433 * decimal representation and returned as a string, exactly as if
434 * the {@code byte} value were given as an argument to the
435 * {@link java.lang.Byte#toString(byte)} method.
436 *
437 * @return a string representation of the value of this object in
438 * base 10.
439 */
440 @Override
441 public String toString() {
442 return Integer.toString(value);
443 }
444
445 /**
446 * Returns a hash code for this {@code Byte}; equal to the result
447 * of invoking {@code intValue()}.
448 *
449 * @return a hash code value for this {@code Byte}
450 */
451 @Override
452 public int hashCode() {
453 return Byte.hashCode(value);
454 }
455
456 /**
457 * Returns a hash code for a {@code byte} value; compatible with
458 * {@code Byte.hashCode()}.
459 *
460 * @param value the value to hash
461 * @return a hash code value for a {@code byte} value.
462 * @since 1.8
463 */
464 public static int hashCode(byte value) {
465 return (int)value;
466 }
467
468 /**
469 * Compares this object to the specified object. The result is
470 * {@code true} if and only if the argument is not
471 * {@code null} and is a {@code Byte} object that
472 * contains the same {@code byte} value as this object.
473 *
474 * @param obj the object to compare with
475 * @return {@code true} if the objects are the same;
476 * {@code false} otherwise.
477 */
478 public boolean equals(Object obj) {
479 if (obj instanceof Byte b) {
480 return value == b.byteValue();
481 }
482 return false;
483 }
484
485 /**
486 * Compares two {@code Byte} objects numerically.
487 *
488 * @param anotherByte the {@code Byte} to be compared.
489 * @return the value {@code 0} if this {@code Byte} is
490 * equal to the argument {@code Byte}; a value less than
491 * {@code 0} if this {@code Byte} is numerically less
492 * than the argument {@code Byte}; and a value greater than
493 * {@code 0} if this {@code Byte} is numerically
494 * greater than the argument {@code Byte} (signed
495 * comparison).
496 * @since 1.2
497 */
498 public int compareTo(Byte anotherByte) {
499 return compare(this.value, anotherByte.value);
500 }
501
502 /**
503 * Compares two {@code byte} values numerically.
504 * The value returned is identical to what would be returned by:
505 * <pre>
506 * Byte.valueOf(x).compareTo(Byte.valueOf(y))
507 * </pre>
508 *
509 * @param x the first {@code byte} to compare
510 * @param y the second {@code byte} to compare
511 * @return the value {@code 0} if {@code x == y};
512 * a value less than {@code 0} if {@code x < y}; and
513 * a value greater than {@code 0} if {@code x > y}
514 * @since 1.7
515 */
516 public static int compare(byte x, byte y) {
517 return x - y;
518 }
519
520 /**
521 * Compares two {@code byte} values numerically treating the values
522 * as unsigned.
523 *
524 * @param x the first {@code byte} to compare
525 * @param y the second {@code byte} to compare
526 * @return the value {@code 0} if {@code x == y}; a value less
527 * than {@code 0} if {@code x < y} as unsigned values; and
528 * a value greater than {@code 0} if {@code x > y} as
529 * unsigned values
530 * @since 9
531 */
532 public static int compareUnsigned(byte x, byte y) {
533 return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y);
534 }
535
536 /**
537 * Converts the argument to an {@code int} by an unsigned
538 * conversion. In an unsigned conversion to an {@code int}, the
539 * high-order 24 bits of the {@code int} are zero and the
540 * low-order 8 bits are equal to the bits of the {@code byte} argument.
541 *
542 * Consequently, zero and positive {@code byte} values are mapped
543 * to a numerically equal {@code int} value and negative {@code
544 * byte} values are mapped to an {@code int} value equal to the
545 * input plus 2<sup>8</sup>.
546 *
547 * @param x the value to convert to an unsigned {@code int}
548 * @return the argument converted to {@code int} by an unsigned
549 * conversion
550 * @since 1.8
551 */
552 public static int toUnsignedInt(byte x) {
553 return ((int) x) & 0xff;
554 }
555
556 /**
557 * Converts the argument to a {@code long} by an unsigned
558 * conversion. In an unsigned conversion to a {@code long}, the
559 * high-order 56 bits of the {@code long} are zero and the
560 * low-order 8 bits are equal to the bits of the {@code byte} argument.
561 *
562 * Consequently, zero and positive {@code byte} values are mapped
563 * to a numerically equal {@code long} value and negative {@code
564 * byte} values are mapped to a {@code long} value equal to the
565 * input plus 2<sup>8</sup>.
566 *
567 * @param x the value to convert to an unsigned {@code long}
568 * @return the argument converted to {@code long} by an unsigned
569 * conversion
570 * @since 1.8
571 */
572 public static long toUnsignedLong(byte x) {
573 return ((long) x) & 0xffL;
574 }
575
576
577 /**
578 * The number of bits used to represent a {@code byte} value in two's
579 * complement binary form.
580 *
581 * @since 1.5
582 */
583 public static final int SIZE = 8;
584
585 /**
586 * The number of bytes used to represent a {@code byte} value in two's
587 * complement binary form.
588 *
589 * @since 1.8
590 */
591 public static final int BYTES = SIZE / Byte.SIZE;
592
593 /** use serialVersionUID from JDK 1.1. for interoperability */
594 @java.io.Serial
595 private static final long serialVersionUID = -7183698231559129828L;
596 }