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.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 * @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 public static final Class<Byte> TYPE = Class.getPrimitiveClass("byte");
83
84 /**
85 * Returns a new {@code String} object representing the
86 * specified {@code byte}. The radix is assumed to be 10.
87 *
88 * @param b the {@code byte} to be converted
89 * @return the string representation of the specified {@code byte}
90 * @see java.lang.Integer#toString(int)
91 */
92 public static String toString(byte b) {
93 return Integer.toString(b);
94 }
95
96 /**
97 * Returns an {@link Optional} containing the nominal descriptor for this
98 * instance.
99 *
100 * @return an {@link Optional} describing the {@linkplain Byte} instance
101 * @since 15
102 */
103 @Override
104 public Optional<DynamicConstantDesc<Byte>> describeConstable() {
105 return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
106 }
107
108 private static final class ByteCache {
109 private ByteCache() {}
110
111 @Stable
112 static final Byte[] cache;
113 static Byte[] archivedCache;
114
115 static {
116 final int size = -(-128) + 127 + 1;
117
118 // Load and use the archived cache if it exists
119 CDS.initializeFromArchive(ByteCache.class);
120 if (archivedCache == null) {
121 Byte[] c = new Byte[size];
122 byte value = (byte)-128;
123 for(int i = 0; i < size; i++) {
124 c[i] = new Byte(value++);
125 }
126 archivedCache = c;
127 }
128 cache = archivedCache;
129 assert cache.length == size;
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 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 b) {
481 return value == b.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 }