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