1 /*
2 * Copyright (c) 1996, 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.value.DeserializeConstructor;
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 {@linkplain #equals(Object) equal}
54 * as interchangeable and should not use instances for synchronization, mutexes, or
55 * with {@linkplain java.lang.ref.Reference object references}.
56 *
57 * <div class="preview-block">
58 * <div class="preview-comment">
59 * When preview features are enabled, {@code Byte} is a {@linkplain Class#isValue value class}.
60 * Use of value class instances for synchronization, mutexes, or with
61 * {@linkplain java.lang.ref.Reference object references} result in
62 * {@link IdentityException}.
63 * </div>
64 * </div>
65 *
66 * @author Nakul Saraiya
67 * @author Joseph D. Darcy
68 * @see java.lang.Number
69 * @since 1.1
70 */
71 @jdk.internal.MigratedValueClass
72 @jdk.internal.ValueBased
73 public final class Byte extends Number implements Comparable<Byte>, Constable {
74
75 /**
76 * A constant holding the minimum value a {@code byte} can
77 * have, -2<sup>7</sup>.
78 */
79 public static final byte MIN_VALUE = -128;
80
81 /**
82 * A constant holding the maximum value a {@code byte} can
83 * have, 2<sup>7</sup>-1.
84 */
85 public static final byte MAX_VALUE = 127;
86
87 /**
88 * The {@code Class} instance representing the primitive type
89 * {@code byte}.
90 */
91 public static final Class<Byte> TYPE = Class.getPrimitiveClass("byte");
92
93 /**
94 * Returns a new {@code String} object representing the
95 * specified {@code byte}. The radix is assumed to be 10.
96 *
97 * @param b the {@code byte} to be converted
98 * @return the string representation of the specified {@code byte}
99 * @see java.lang.Integer#toString(int)
100 */
101 public static String toString(byte b) {
102 return Integer.toString(b);
103 }
104
105 /**
106 * Returns an {@link Optional} containing the nominal descriptor for this
107 * instance.
108 *
109 * @return an {@link Optional} describing the {@linkplain Byte} instance
110 * @since 15
111 */
112 @Override
113 public Optional<DynamicConstantDesc<Byte>> describeConstable() {
114 return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
115 }
116
117 private static final class ByteCache {
118 private ByteCache() {}
119
120 @Stable
121 static final Byte[] cache;
122 static Byte[] archivedCache;
123
124 static {
125 final int size = -(-128) + 127 + 1;
126
127 // Load and use the archived cache if it exists
128 CDS.initializeFromArchive(ByteCache.class);
129 if (archivedCache == null) {
130 Byte[] c = new Byte[size];
131 byte value = (byte)-128;
132 for(int i = 0; i < size; i++) {
133 c[i] = new Byte(value++);
134 }
135 archivedCache = c;
136 }
137 cache = archivedCache;
138 assert cache.length == size;
139 }
140 }
141
142 /**
143 * Returns a {@code Byte} instance representing the specified
144 * {@code byte} value.
145 * If a new {@code Byte} instance is not required, this method
146 * should generally be used in preference to the constructor
147 * {@link #Byte(byte)}, as this method is likely to yield
148 * significantly better space and time performance since
149 * all byte values are cached.
150 *
151 * @param b a byte value.
152 * @return a {@code Byte} instance representing {@code b}.
153 * @since 1.5
154 */
155 @IntrinsicCandidate
156 @DeserializeConstructor
157 public static Byte valueOf(byte b) {
158 final int offset = 128;
159 return ByteCache.cache[(int)b + offset];
160 }
161
162 /**
163 * Parses the string argument as a signed {@code byte} in the
164 * radix specified by the second argument. The characters in the
165 * string must all be digits, of the specified radix (as
166 * determined by whether {@link java.lang.Character#digit(char,
167 * int)} returns a nonnegative value) except that the first
168 * character may be an ASCII minus sign {@code '-'}
169 * ({@code '\u005Cu002D'}) to indicate a negative value or an
170 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
171 * indicate a positive value. The resulting {@code byte} value is
172 * returned.
173 *
174 * <p>An exception of type {@code NumberFormatException} is
175 * thrown if any of the following situations occurs:
176 * <ul>
177 * <li> The first argument is {@code null} or is a string of
178 * length zero.
179 *
180 * <li> The radix is either smaller than {@link
181 * java.lang.Character#MIN_RADIX} or larger than {@link
182 * java.lang.Character#MAX_RADIX}.
183 *
184 * <li> Any character of the string is not a digit of the
185 * specified radix, except that the first character may be a minus
186 * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
187 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
188 * string is longer than length 1.
189 *
190 * <li> The value represented by the string is not a value of type
191 * {@code byte}.
192 * </ul>
193 *
194 * @param s the {@code String} containing the
195 * {@code byte}
196 * representation to be parsed
197 * @param radix the radix to be used while parsing {@code s}
198 * @return the {@code byte} value represented by the string
199 * argument in the specified radix
200 * @throws NumberFormatException If the string does
201 * not contain a parsable {@code byte}.
202 */
203 public static byte parseByte(String s, int radix)
204 throws NumberFormatException {
205 int i = Integer.parseInt(s, radix);
206 if (i < MIN_VALUE || i > MAX_VALUE)
207 throw new NumberFormatException(
208 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
209 return (byte)i;
210 }
211
212 /**
213 * Parses the string argument as a signed decimal {@code
214 * byte}. The characters in the string must all be decimal digits,
215 * except that the first character may be an ASCII minus sign
216 * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
217 * value or an ASCII plus sign {@code '+'}
218 * ({@code '\u005Cu002B'}) to indicate a positive value. The
219 * resulting {@code byte} value is returned, exactly as if the
220 * argument and the radix 10 were given as arguments to the {@link
221 * #parseByte(java.lang.String, int)} method.
222 *
223 * @param s a {@code String} containing the
224 * {@code byte} representation to be parsed
225 * @return the {@code byte} value represented by the
226 * argument in decimal
227 * @throws NumberFormatException if the string does not
228 * contain a parsable {@code byte}.
229 */
230 public static byte parseByte(String s) throws NumberFormatException {
231 return parseByte(s, 10);
232 }
233
234 /**
235 * Returns a {@code Byte} object holding the value
236 * extracted from the specified {@code String} when parsed
237 * with the radix given by the second argument. The first argument
238 * is interpreted as representing a signed {@code byte} in
239 * the radix specified by the second argument, exactly as if the
240 * argument were given to the {@link #parseByte(java.lang.String,
241 * int)} method. The result is a {@code Byte} object that
242 * represents the {@code byte} value specified by the string.
243 *
244 * <p> In other words, this method returns a {@code Byte} object
245 * equal to the value of:
246 *
247 * <blockquote>
248 * {@code Byte.valueOf(Byte.parseByte(s, radix))}
249 * </blockquote>
250 *
251 * @param s the string to be parsed
252 * @param radix the radix to be used in interpreting {@code s}
253 * @return a {@code Byte} object holding the value
254 * represented by the string argument in the
255 * specified radix.
256 * @throws NumberFormatException If the {@code String} does
257 * not contain a parsable {@code byte}.
258 */
259 public static Byte valueOf(String s, int radix)
260 throws NumberFormatException {
261 return valueOf(parseByte(s, radix));
262 }
263
264 /**
265 * Returns a {@code Byte} object holding the value
266 * given by the specified {@code String}. The argument is
267 * interpreted as representing a signed decimal {@code byte},
268 * exactly as if the argument were given to the {@link
269 * #parseByte(java.lang.String)} method. The result is a
270 * {@code Byte} object that represents the {@code byte}
271 * value specified by the string.
272 *
273 * <p> In other words, this method returns a {@code Byte} object
274 * equal to the value of:
275 *
276 * <blockquote>
277 * {@code Byte.valueOf(Byte.parseByte(s))}
278 * </blockquote>
279 *
280 * @param s the string to be parsed
281 * @return a {@code Byte} object holding the value
282 * represented by the string argument
283 * @throws NumberFormatException If the {@code String} does
284 * not contain a parsable {@code byte}.
285 */
286 public static Byte valueOf(String s) throws NumberFormatException {
287 return valueOf(s, 10);
288 }
289
290 /**
291 * Decodes a {@code String} into a {@code Byte}.
292 * Accepts decimal, hexadecimal, and octal numbers given by
293 * the following grammar:
294 *
295 * <blockquote>
296 * <dl>
297 * <dt><i>DecodableString:</i>
298 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
299 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
300 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
301 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
302 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
303 *
304 * <dt><i>Sign:</i>
305 * <dd>{@code -}
306 * <dd>{@code +}
307 * </dl>
308 * </blockquote>
309 *
310 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
311 * are as defined in section {@jls 3.10.1} of
312 * <cite>The Java Language Specification</cite>,
313 * except that underscores are not accepted between digits.
314 *
315 * <p>The sequence of characters following an optional
316 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
317 * "{@code #}", or leading zero) is parsed as by the {@code
318 * Byte.parseByte} method with the indicated radix (10, 16, or 8).
319 * This sequence of characters must represent a positive value or
320 * a {@link NumberFormatException} will be thrown. The result is
321 * negated if first character of the specified {@code String} is
322 * the minus sign. No whitespace characters are permitted in the
323 * {@code String}.
324 *
325 * @param nm the {@code String} to decode.
326 * @return a {@code Byte} object holding the {@code byte}
327 * value represented by {@code nm}
328 * @throws NumberFormatException if the {@code String} does not
329 * contain a parsable {@code byte}.
330 * @see java.lang.Byte#parseByte(java.lang.String, int)
331 */
332 public static Byte decode(String nm) throws NumberFormatException {
333 int i = Integer.decode(nm);
334 if (i < MIN_VALUE || i > MAX_VALUE)
335 throw new NumberFormatException(
336 "Value " + i + " out of range from input " + nm);
337 return valueOf((byte)i);
338 }
339
340 /**
341 * The value of the {@code Byte}.
342 *
343 * @serial
344 */
345 private final byte value;
346
347 /**
348 * Constructs a newly allocated {@code Byte} object that
349 * represents the specified {@code byte} value.
350 *
351 * @param value the value to be represented by the
352 * {@code Byte}.
353 *
354 * @deprecated
355 * It is rarely appropriate to use this constructor. The static factory
356 * {@link #valueOf(byte)} is generally a better choice, as it is
357 * likely to yield significantly better space and time performance.
358 */
359 @Deprecated(since="9", forRemoval = true)
360 public Byte(byte value) {
361 this.value = value;
362 }
363
364 /**
365 * Constructs a newly allocated {@code Byte} object that
366 * represents the {@code byte} value indicated by the
367 * {@code String} parameter. The string is converted to a
368 * {@code byte} value in exactly the manner used by the
369 * {@code parseByte} method for radix 10.
370 *
371 * @param s the {@code String} to be converted to a
372 * {@code Byte}
373 * @throws NumberFormatException if the {@code String}
374 * does not contain a parsable {@code byte}.
375 *
376 * @deprecated
377 * It is rarely appropriate to use this constructor.
378 * Use {@link #parseByte(String)} to convert a string to a
379 * {@code byte} primitive, or use {@link #valueOf(String)}
380 * to convert a string to a {@code Byte} object.
381 */
382 @Deprecated(since="9", forRemoval = true)
383 public Byte(String s) throws NumberFormatException {
384 this.value = parseByte(s, 10);
385 }
386
387 /**
388 * Returns the value of this {@code Byte} as a
389 * {@code byte}.
390 */
391 @IntrinsicCandidate
392 public byte byteValue() {
393 return value;
394 }
395
396 /**
397 * Returns the value of this {@code Byte} as a {@code short} after
398 * a widening primitive conversion.
399 * @jls 5.1.2 Widening Primitive Conversion
400 */
401 public short shortValue() {
402 return (short)value;
403 }
404
405 /**
406 * Returns the value of this {@code Byte} as an {@code int} after
407 * a widening primitive conversion.
408 * @jls 5.1.2 Widening Primitive Conversion
409 */
410 public int intValue() {
411 return (int)value;
412 }
413
414 /**
415 * Returns the value of this {@code Byte} as a {@code long} after
416 * a widening primitive conversion.
417 * @jls 5.1.2 Widening Primitive Conversion
418 */
419 public long longValue() {
420 return (long)value;
421 }
422
423 /**
424 * Returns the value of this {@code Byte} as a {@code float} after
425 * a widening primitive conversion.
426 * @jls 5.1.2 Widening Primitive Conversion
427 */
428 public float floatValue() {
429 return (float)value;
430 }
431
432 /**
433 * Returns the value of this {@code Byte} as a {@code double}
434 * after a widening primitive conversion.
435 * @jls 5.1.2 Widening Primitive Conversion
436 */
437 public double doubleValue() {
438 return (double)value;
439 }
440
441 /**
442 * Returns a {@code String} object representing this
443 * {@code Byte}'s value. The value is converted to signed
444 * decimal representation and returned as a string, exactly as if
445 * the {@code byte} value were given as an argument to the
446 * {@link java.lang.Byte#toString(byte)} method.
447 *
448 * @return a string representation of the value of this object in
449 * base 10.
450 */
451 @Override
452 public String toString() {
453 return Integer.toString(value);
454 }
455
456 /**
457 * Returns a hash code for this {@code Byte}; equal to the result
458 * of invoking {@code intValue()}.
459 *
460 * @return a hash code value for this {@code Byte}
461 */
462 @Override
463 public int hashCode() {
464 return Byte.hashCode(value);
465 }
466
467 /**
468 * Returns a hash code for a {@code byte} value; compatible with
469 * {@code Byte.hashCode()}.
470 *
471 * @param value the value to hash
472 * @return a hash code value for a {@code byte} value.
473 * @since 1.8
474 */
475 public static int hashCode(byte value) {
476 return (int)value;
477 }
478
479 /**
480 * Compares this object to the specified object. The result is
481 * {@code true} if and only if the argument is not
482 * {@code null} and is a {@code Byte} object that
483 * contains the same {@code byte} value as this object.
484 *
485 * @param obj the object to compare with
486 * @return {@code true} if the objects are the same;
487 * {@code false} otherwise.
488 */
489 public boolean equals(Object obj) {
490 if (obj instanceof Byte b) {
491 return value == b.byteValue();
492 }
493 return false;
494 }
495
496 /**
497 * Compares two {@code Byte} objects numerically.
498 *
499 * @param anotherByte the {@code Byte} to be compared.
500 * @return the value {@code 0} if this {@code Byte} is
501 * equal to the argument {@code Byte}; a value less than
502 * {@code 0} if this {@code Byte} is numerically less
503 * than the argument {@code Byte}; and a value greater than
504 * {@code 0} if this {@code Byte} is numerically
505 * greater than the argument {@code Byte} (signed
506 * comparison).
507 * @since 1.2
508 */
509 public int compareTo(Byte anotherByte) {
510 return compare(this.value, anotherByte.value);
511 }
512
513 /**
514 * Compares two {@code byte} values numerically.
515 * The value returned is identical to what would be returned by:
516 * <pre>
517 * Byte.valueOf(x).compareTo(Byte.valueOf(y))
518 * </pre>
519 *
520 * @param x the first {@code byte} to compare
521 * @param y the second {@code byte} to compare
522 * @return the value {@code 0} if {@code x == y};
523 * a value less than {@code 0} if {@code x < y}; and
524 * a value greater than {@code 0} if {@code x > y}
525 * @since 1.7
526 */
527 public static int compare(byte x, byte y) {
528 return x - y;
529 }
530
531 /**
532 * Compares two {@code byte} values numerically treating the values
533 * as unsigned.
534 *
535 * @param x the first {@code byte} to compare
536 * @param y the second {@code byte} to compare
537 * @return the value {@code 0} if {@code x == y}; a value less
538 * than {@code 0} if {@code x < y} as unsigned values; and
539 * a value greater than {@code 0} if {@code x > y} as
540 * unsigned values
541 * @since 9
542 */
543 public static int compareUnsigned(byte x, byte y) {
544 return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y);
545 }
546
547 /**
548 * Converts the argument to an {@code int} by an unsigned
549 * conversion. In an unsigned conversion to an {@code int}, the
550 * high-order 24 bits of the {@code int} are zero and the
551 * low-order 8 bits are equal to the bits of the {@code byte} argument.
552 *
553 * Consequently, zero and positive {@code byte} values are mapped
554 * to a numerically equal {@code int} value and negative {@code
555 * byte} values are mapped to an {@code int} value equal to the
556 * input plus 2<sup>8</sup>.
557 *
558 * @param x the value to convert to an unsigned {@code int}
559 * @return the argument converted to {@code int} by an unsigned
560 * conversion
561 * @since 1.8
562 */
563 public static int toUnsignedInt(byte x) {
564 return ((int) x) & 0xff;
565 }
566
567 /**
568 * Converts the argument to a {@code long} by an unsigned
569 * conversion. In an unsigned conversion to a {@code long}, the
570 * high-order 56 bits of the {@code long} are zero and the
571 * low-order 8 bits are equal to the bits of the {@code byte} argument.
572 *
573 * Consequently, zero and positive {@code byte} values are mapped
574 * to a numerically equal {@code long} value and negative {@code
575 * byte} values are mapped to a {@code long} value equal to the
576 * input plus 2<sup>8</sup>.
577 *
578 * @param x the value to convert to an unsigned {@code long}
579 * @return the argument converted to {@code long} by an unsigned
580 * conversion
581 * @since 1.8
582 */
583 public static long toUnsignedLong(byte x) {
584 return ((long) x) & 0xffL;
585 }
586
587
588 /**
589 * The number of bits used to represent a {@code byte} value in two's
590 * complement binary form.
591 *
592 * @since 1.5
593 */
594 public static final int SIZE = 8;
595
596 /**
597 * The number of bytes used to represent a {@code byte} value in two's
598 * complement binary form.
599 *
600 * @since 1.8
601 */
602 public static final int BYTES = SIZE / Byte.SIZE;
603
604 /** use serialVersionUID from JDK 1.1. for interoperability */
605 @java.io.Serial
606 private static final long serialVersionUID = -7183698231559129828L;
607 }