1 /*
2 * Copyright (c) 1996, 2023, 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 *
43 * The {@code Byte} class wraps a value of primitive type {@code byte}
44 * in an object. An object of type {@code Byte} contains a single
45 * 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 @SuppressWarnings("unchecked")
84 public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
85
86 /**
87 * Returns a new {@code String} object representing the
88 * specified {@code byte}. The radix is assumed to be 10.
89 *
90 * @param b the {@code byte} to be converted
91 * @return the string representation of the specified {@code byte}
92 * @see java.lang.Integer#toString(int)
93 */
94 public static String toString(byte b) {
95 return Integer.toString(b);
96 }
97
98 /**
99 * Returns an {@link Optional} containing the nominal descriptor for this
100 * instance.
101 *
102 * @return an {@link Optional} describing the {@linkplain Byte} instance
103 * @since 15
104 */
105 @Override
106 public Optional<DynamicConstantDesc<Byte>> describeConstable() {
107 return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
108 }
109
110 private static final class ByteCache {
111 private ByteCache() {}
112
113 @Stable
114 static final Byte[] cache;
115 static Byte[] archivedCache;
116
117 static {
118 final int size = -(-128) + 127 + 1;
119
120 // Load and use the archived cache if it exists
121 CDS.initializeFromArchive(ByteCache.class);
122 if (archivedCache == null || archivedCache.length != size) {
123 Byte[] c = new Byte[size];
124 byte value = (byte)-128;
125 for(int i = 0; i < size; i++) {
126 c[i] = new Byte(value++);
127 }
128 archivedCache = c;
129 }
130 cache = archivedCache;
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 public static Byte valueOf(byte b) {
149 final int offset = 128;
150 return ByteCache.cache[(int)b + offset];
151 }
152
153 /**
154 * Parses the string argument as a signed {@code byte} in the
155 * radix specified by the second argument. The characters in the
156 * string must all be digits, of the specified radix (as
157 * determined by whether {@link java.lang.Character#digit(char,
158 * int)} returns a nonnegative value) except that the first
159 * character may be an ASCII minus sign {@code '-'}
160 * ({@code '\u005Cu002D'}) to indicate a negative value or an
161 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
162 * indicate a positive value. The resulting {@code byte} value is
163 * returned.
164 *
165 * <p>An exception of type {@code NumberFormatException} is
166 * thrown if any of the following situations occurs:
167 * <ul>
168 * <li> The first argument is {@code null} or is a string of
169 * length zero.
170 *
171 * <li> The radix is either smaller than {@link
172 * java.lang.Character#MIN_RADIX} or larger than {@link
173 * java.lang.Character#MAX_RADIX}.
174 *
175 * <li> Any character of the string is not a digit of the
176 * specified radix, except that the first character may be a minus
177 * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
178 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
179 * string is longer than length 1.
180 *
181 * <li> The value represented by the string is not a value of type
182 * {@code byte}.
183 * </ul>
184 *
185 * @param s the {@code String} containing the
186 * {@code byte}
187 * representation to be parsed
188 * @param radix the radix to be used while parsing {@code s}
189 * @return the {@code byte} value represented by the string
190 * argument in the specified radix
191 * @throws NumberFormatException If the string does
192 * not contain a parsable {@code byte}.
193 */
194 public static byte parseByte(String s, int radix)
195 throws NumberFormatException {
196 int i = Integer.parseInt(s, radix);
197 if (i < MIN_VALUE || i > MAX_VALUE)
198 throw new NumberFormatException(
199 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
200 return (byte)i;
201 }
202
203 /**
204 * Parses the string argument as a signed decimal {@code
205 * byte}. The characters in the string must all be decimal digits,
206 * except that the first character may be an ASCII minus sign
207 * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
208 * value or an ASCII plus sign {@code '+'}
209 * ({@code '\u005Cu002B'}) to indicate a positive value. The
210 * resulting {@code byte} value is returned, exactly as if the
211 * argument and the radix 10 were given as arguments to the {@link
212 * #parseByte(java.lang.String, int)} method.
213 *
214 * @param s a {@code String} containing the
215 * {@code byte} representation to be parsed
216 * @return the {@code byte} value represented by the
217 * argument in decimal
218 * @throws NumberFormatException if the string does not
219 * contain a parsable {@code byte}.
220 */
221 public static byte parseByte(String s) throws NumberFormatException {
222 return parseByte(s, 10);
223 }
224
225 /**
226 * Returns a {@code Byte} object holding the value
227 * extracted from the specified {@code String} when parsed
228 * with the radix given by the second argument. The first argument
229 * is interpreted as representing a signed {@code byte} in
230 * the radix specified by the second argument, exactly as if the
231 * argument were given to the {@link #parseByte(java.lang.String,
232 * int)} method. The result is a {@code Byte} object that
233 * represents the {@code byte} value specified by the string.
234 *
235 * <p> In other words, this method returns a {@code Byte} object
236 * equal to the value of:
237 *
238 * <blockquote>
239 * {@code Byte.valueOf(Byte.parseByte(s, radix))}
240 * </blockquote>
241 *
242 * @param s the string to be parsed
243 * @param radix the radix to be used in interpreting {@code s}
244 * @return a {@code Byte} object holding the value
245 * represented by the string argument in the
246 * specified radix.
247 * @throws NumberFormatException If the {@code String} does
248 * not contain a parsable {@code byte}.
249 */
250 public static Byte valueOf(String s, int radix)
251 throws NumberFormatException {
252 return valueOf(parseByte(s, radix));
253 }
254
255 /**
256 * Returns a {@code Byte} object holding the value
257 * given by the specified {@code String}. The argument is
258 * interpreted as representing a signed decimal {@code byte},
259 * exactly as if the argument were given to the {@link
260 * #parseByte(java.lang.String)} method. The result is a
261 * {@code Byte} object that represents the {@code byte}
262 * value specified by the string.
263 *
264 * <p> In other words, this method returns a {@code Byte} object
265 * equal to the value of:
266 *
267 * <blockquote>
268 * {@code Byte.valueOf(Byte.parseByte(s))}
269 * </blockquote>
270 *
271 * @param s the string to be parsed
272 * @return a {@code Byte} object holding the value
273 * represented by the string argument
274 * @throws NumberFormatException If the {@code String} does
275 * not contain a parsable {@code byte}.
276 */
277 public static Byte valueOf(String s) throws NumberFormatException {
278 return valueOf(s, 10);
279 }
280
281 /**
282 * Decodes a {@code String} into a {@code Byte}.
283 * Accepts decimal, hexadecimal, and octal numbers given by
284 * the following grammar:
285 *
286 * <blockquote>
287 * <dl>
288 * <dt><i>DecodableString:</i>
289 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
290 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
291 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
292 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
293 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
294 *
295 * <dt><i>Sign:</i>
296 * <dd>{@code -}
297 * <dd>{@code +}
298 * </dl>
299 * </blockquote>
300 *
301 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
302 * are as defined in section {@jls 3.10.1} of
303 * <cite>The Java Language Specification</cite>,
304 * except that underscores are not accepted between digits.
305 *
306 * <p>The sequence of characters following an optional
307 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
308 * "{@code #}", or leading zero) is parsed as by the {@code
309 * Byte.parseByte} method with the indicated radix (10, 16, or 8).
310 * This sequence of characters must represent a positive value or
311 * a {@link NumberFormatException} will be thrown. The result is
312 * negated if first character of the specified {@code String} is
313 * the minus sign. No whitespace characters are permitted in the
314 * {@code String}.
315 *
316 * @param nm the {@code String} to decode.
317 * @return a {@code Byte} object holding the {@code byte}
318 * value represented by {@code nm}
319 * @throws NumberFormatException if the {@code String} does not
320 * contain a parsable {@code byte}.
321 * @see java.lang.Byte#parseByte(java.lang.String, int)
322 */
323 public static Byte decode(String nm) throws NumberFormatException {
324 int i = Integer.decode(nm);
325 if (i < MIN_VALUE || i > MAX_VALUE)
326 throw new NumberFormatException(
327 "Value " + i + " out of range from input " + nm);
328 return valueOf((byte)i);
329 }
330
331 /**
332 * The value of the {@code Byte}.
333 *
334 * @serial
335 */
336 private final byte value;
337
338 /**
339 * Constructs a newly allocated {@code Byte} object that
340 * represents the specified {@code byte} value.
341 *
342 * @param value the value to be represented by the
343 * {@code Byte}.
344 *
345 * @deprecated
346 * It is rarely appropriate to use this constructor. The static factory
347 * {@link #valueOf(byte)} is generally a better choice, as it is
348 * likely to yield significantly better space and time performance.
349 */
350 @Deprecated(since="9", forRemoval = true)
351 public Byte(byte value) {
352 this.value = value;
353 }
354
355 /**
356 * Constructs a newly allocated {@code Byte} object that
357 * represents the {@code byte} value indicated by the
358 * {@code String} parameter. The string is converted to a
359 * {@code byte} value in exactly the manner used by the
360 * {@code parseByte} method for radix 10.
361 *
362 * @param s the {@code String} to be converted to a
363 * {@code Byte}
364 * @throws NumberFormatException if the {@code String}
365 * does not contain a parsable {@code byte}.
366 *
367 * @deprecated
368 * It is rarely appropriate to use this constructor.
369 * Use {@link #parseByte(String)} to convert a string to a
370 * {@code byte} primitive, or use {@link #valueOf(String)}
371 * to convert a string to a {@code Byte} object.
372 */
373 @Deprecated(since="9", forRemoval = true)
374 public Byte(String s) throws NumberFormatException {
375 this.value = parseByte(s, 10);
376 }
377
378 /**
379 * Returns the value of this {@code Byte} as a
380 * {@code byte}.
381 */
382 @IntrinsicCandidate
383 public byte byteValue() {
384 return value;
385 }
386
387 /**
388 * Returns the value of this {@code Byte} as a {@code short} after
389 * a widening primitive conversion.
390 * @jls 5.1.2 Widening Primitive Conversion
391 */
392 public short shortValue() {
393 return (short)value;
394 }
395
396 /**
397 * Returns the value of this {@code Byte} as an {@code int} after
398 * a widening primitive conversion.
399 * @jls 5.1.2 Widening Primitive Conversion
400 */
401 public int intValue() {
402 return (int)value;
403 }
404
405 /**
406 * Returns the value of this {@code Byte} as a {@code long} after
407 * a widening primitive conversion.
408 * @jls 5.1.2 Widening Primitive Conversion
409 */
410 public long longValue() {
411 return (long)value;
412 }
413
414 /**
415 * Returns the value of this {@code Byte} as a {@code float} after
416 * a widening primitive conversion.
417 * @jls 5.1.2 Widening Primitive Conversion
418 */
419 public float floatValue() {
420 return (float)value;
421 }
422
423 /**
424 * Returns the value of this {@code Byte} as a {@code double}
425 * after a widening primitive conversion.
426 * @jls 5.1.2 Widening Primitive Conversion
427 */
428 public double doubleValue() {
429 return (double)value;
430 }
431
432 /**
433 * Returns a {@code String} object representing this
434 * {@code Byte}'s value. The value is converted to signed
435 * decimal representation and returned as a string, exactly as if
436 * the {@code byte} value were given as an argument to the
437 * {@link java.lang.Byte#toString(byte)} method.
438 *
439 * @return a string representation of the value of this object in
440 * base 10.
441 */
442 @Override
443 public String toString() {
444 return Integer.toString(value);
445 }
446
447 /**
448 * Returns a hash code for this {@code Byte}; equal to the result
449 * of invoking {@code intValue()}.
450 *
451 * @return a hash code value for this {@code Byte}
452 */
453 @Override
454 public int hashCode() {
455 return Byte.hashCode(value);
456 }
457
458 /**
459 * Returns a hash code for a {@code byte} value; compatible with
460 * {@code Byte.hashCode()}.
461 *
462 * @param value the value to hash
463 * @return a hash code value for a {@code byte} value.
464 * @since 1.8
465 */
466 public static int hashCode(byte value) {
467 return (int)value;
468 }
469
470 /**
471 * Compares this object to the specified object. The result is
472 * {@code true} if and only if the argument is not
473 * {@code null} and is a {@code Byte} object that
474 * contains the same {@code byte} value as this object.
475 *
476 * @param obj the object to compare with
477 * @return {@code true} if the objects are the same;
478 * {@code false} otherwise.
479 */
480 public boolean equals(Object obj) {
481 if (obj instanceof Byte) {
482 return value == ((Byte)obj).byteValue();
483 }
484 return false;
485 }
486
487 /**
488 * Compares two {@code Byte} objects numerically.
489 *
490 * @param anotherByte the {@code Byte} to be compared.
491 * @return the value {@code 0} if this {@code Byte} is
492 * equal to the argument {@code Byte}; a value less than
493 * {@code 0} if this {@code Byte} is numerically less
494 * than the argument {@code Byte}; and a value greater than
495 * {@code 0} if this {@code Byte} is numerically
496 * greater than the argument {@code Byte} (signed
497 * comparison).
498 * @since 1.2
499 */
500 public int compareTo(Byte anotherByte) {
501 return compare(this.value, anotherByte.value);
502 }
503
504 /**
505 * Compares two {@code byte} values numerically.
506 * The value returned is identical to what would be returned by:
507 * <pre>
508 * Byte.valueOf(x).compareTo(Byte.valueOf(y))
509 * </pre>
510 *
511 * @param x the first {@code byte} to compare
512 * @param y the second {@code byte} to compare
513 * @return the value {@code 0} if {@code x == y};
514 * a value less than {@code 0} if {@code x < y}; and
515 * a value greater than {@code 0} if {@code x > y}
516 * @since 1.7
517 */
518 public static int compare(byte x, byte y) {
519 return x - y;
520 }
521
522 /**
523 * Compares two {@code byte} values numerically treating the values
524 * as unsigned.
525 *
526 * @param x the first {@code byte} to compare
527 * @param y the second {@code byte} to compare
528 * @return the value {@code 0} if {@code x == y}; a value less
529 * than {@code 0} if {@code x < y} as unsigned values; and
530 * a value greater than {@code 0} if {@code x > y} as
531 * unsigned values
532 * @since 9
533 */
534 public static int compareUnsigned(byte x, byte y) {
535 return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y);
536 }
537
538 /**
539 * Converts the argument to an {@code int} by an unsigned
540 * conversion. In an unsigned conversion to an {@code int}, the
541 * high-order 24 bits of the {@code int} are zero and the
542 * low-order 8 bits are equal to the bits of the {@code byte} argument.
543 *
544 * Consequently, zero and positive {@code byte} values are mapped
545 * to a numerically equal {@code int} value and negative {@code
546 * byte} values are mapped to an {@code int} value equal to the
547 * input plus 2<sup>8</sup>.
548 *
549 * @param x the value to convert to an unsigned {@code int}
550 * @return the argument converted to {@code int} by an unsigned
551 * conversion
552 * @since 1.8
553 */
554 public static int toUnsignedInt(byte x) {
555 return ((int) x) & 0xff;
556 }
557
558 /**
559 * Converts the argument to a {@code long} by an unsigned
560 * conversion. In an unsigned conversion to a {@code long}, the
561 * high-order 56 bits of the {@code long} are zero and the
562 * low-order 8 bits are equal to the bits of the {@code byte} argument.
563 *
564 * Consequently, zero and positive {@code byte} values are mapped
565 * to a numerically equal {@code long} value and negative {@code
566 * byte} values are mapped to a {@code long} value equal to the
567 * input plus 2<sup>8</sup>.
568 *
569 * @param x the value to convert to an unsigned {@code long}
570 * @return the argument converted to {@code long} by an unsigned
571 * conversion
572 * @since 1.8
573 */
574 public static long toUnsignedLong(byte x) {
575 return ((long) x) & 0xffL;
576 }
577
578
579 /**
580 * The number of bits used to represent a {@code byte} value in two's
581 * complement binary form.
582 *
583 * @since 1.5
584 */
585 public static final int SIZE = 8;
586
587 /**
588 * The number of bytes used to represent a {@code byte} value in two's
589 * complement binary form.
590 *
591 * @since 1.8
592 */
593 public static final int BYTES = SIZE / Byte.SIZE;
594
595 /** use serialVersionUID from JDK 1.1. for interoperability */
596 @java.io.Serial
597 private static final long serialVersionUID = -7183698231559129828L;
598 }