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