1 /*
2 * Copyright (c) 1996, 2013, 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.HotSpotIntrinsicCandidate;
29 import jdk.internal.misc.VM;
30
31 /**
32 *
33 * The {@code Byte} class wraps a value of primitive type {@code byte}
34 * in an object. An object of type {@code Byte} contains a single
35 * field whose type is {@code byte}.
36 *
37 * <p>In addition, this class provides several methods for converting
38 * a {@code byte} to a {@code String} and a {@code String} to a {@code
39 * byte}, as well as other constants and methods useful when dealing
40 * with a {@code byte}.
41 *
42 * @author Nakul Saraiya
43 * @author Joseph D. Darcy
44 * @see java.lang.Number
45 * @since 1.1
46 */
47 public final class Byte extends Number implements Comparable<Byte> {
48
49 /**
50 * A constant holding the minimum value a {@code byte} can
51 * have, -2<sup>7</sup>.
52 */
53 public static final byte MIN_VALUE = -128;
54
55 /**
56 * A constant holding the maximum value a {@code byte} can
57 * have, 2<sup>7</sup>-1.
58 */
59 public static final byte MAX_VALUE = 127;
60
61 /**
62 * The {@code Class} instance representing the primitive type
63 * {@code byte}.
64 */
65 @SuppressWarnings("unchecked")
66 public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
67
68 /**
69 * Returns a new {@code String} object representing the
70 * specified {@code byte}. The radix is assumed to be 10.
71 *
72 * @param b the {@code byte} to be converted
73 * @return the string representation of the specified {@code byte}
74 * @see java.lang.Integer#toString(int)
75 */
76 public static String toString(byte b) {
77 return Integer.toString((int)b, 10);
78 }
79
80 private static class ByteCache {
81 private ByteCache() {}
82
83 static final Byte[] cache;
84 static Byte[] archivedCache;
85
86 static {
87 final int size = -(-128) + 127 + 1;
88
89 // Load and use the archived cache if it exists
90 VM.initializeFromArchive(ByteCache.class);
91 if (archivedCache == null || archivedCache.length != size) {
92 Byte[] c = new Byte[size];
93 byte value = (byte)-128;
94 for(int i = 0; i < size; i++) {
95 c[i] = new Byte(value++);
96 }
97 archivedCache = c;
98 }
99 cache = archivedCache;
100 }
101 }
102
103 /**
104 * Returns a {@code Byte} instance representing the specified
105 * {@code byte} value.
106 * If a new {@code Byte} instance is not required, this method
107 * should generally be used in preference to the constructor
108 * {@link #Byte(byte)}, as this method is likely to yield
109 * significantly better space and time performance since
110 * all byte values are cached.
111 *
112 * @param b a byte value.
113 * @return a {@code Byte} instance representing {@code b}.
114 * @since 1.5
115 */
116 @HotSpotIntrinsicCandidate
117 public static Byte valueOf(byte b) {
118 final int offset = 128;
119 return ByteCache.cache[(int)b + offset];
120 }
121
122 /**
123 * Parses the string argument as a signed {@code byte} in the
124 * radix specified by the second argument. The characters in the
125 * string must all be digits, of the specified radix (as
126 * determined by whether {@link java.lang.Character#digit(char,
127 * int)} returns a nonnegative value) except that the first
128 * character may be an ASCII minus sign {@code '-'}
129 * ({@code '\u005Cu002D'}) to indicate a negative value or an
130 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
131 * indicate a positive value. The resulting {@code byte} value is
132 * returned.
133 *
134 * <p>An exception of type {@code NumberFormatException} is
135 * thrown if any of the following situations occurs:
136 * <ul>
137 * <li> The first argument is {@code null} or is a string of
138 * length zero.
139 *
140 * <li> The radix is either smaller than {@link
141 * java.lang.Character#MIN_RADIX} or larger than {@link
142 * java.lang.Character#MAX_RADIX}.
143 *
144 * <li> Any character of the string is not a digit of the
145 * specified radix, except that the first character may be a minus
146 * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
147 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
148 * string is longer than length 1.
149 *
150 * <li> The value represented by the string is not a value of type
151 * {@code byte}.
152 * </ul>
153 *
154 * @param s the {@code String} containing the
155 * {@code byte}
156 * representation to be parsed
157 * @param radix the radix to be used while parsing {@code s}
158 * @return the {@code byte} value represented by the string
159 * argument in the specified radix
160 * @throws NumberFormatException If the string does
161 * not contain a parsable {@code byte}.
162 */
163 public static byte parseByte(String s, int radix)
164 throws NumberFormatException {
165 int i = Integer.parseInt(s, radix);
166 if (i < MIN_VALUE || i > MAX_VALUE)
167 throw new NumberFormatException(
168 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
169 return (byte)i;
170 }
171
172 /**
173 * Parses the string argument as a signed decimal {@code
174 * byte}. The characters in the string must all be decimal digits,
175 * except that the first character may be an ASCII minus sign
176 * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
177 * value or an ASCII plus sign {@code '+'}
178 * ({@code '\u005Cu002B'}) to indicate a positive value. The
179 * resulting {@code byte} value is returned, exactly as if the
180 * argument and the radix 10 were given as arguments to the {@link
181 * #parseByte(java.lang.String, int)} method.
182 *
183 * @param s a {@code String} containing the
184 * {@code byte} representation to be parsed
185 * @return the {@code byte} value represented by the
186 * argument in decimal
187 * @throws NumberFormatException if the string does not
188 * contain a parsable {@code byte}.
189 */
190 public static byte parseByte(String s) throws NumberFormatException {
191 return parseByte(s, 10);
192 }
193
194 /**
195 * Returns a {@code Byte} object holding the value
196 * extracted from the specified {@code String} when parsed
197 * with the radix given by the second argument. The first argument
198 * is interpreted as representing a signed {@code byte} in
199 * the radix specified by the second argument, exactly as if the
200 * argument were given to the {@link #parseByte(java.lang.String,
201 * int)} method. The result is a {@code Byte} object that
202 * represents the {@code byte} value specified by the string.
203 *
204 * <p> In other words, this method returns a {@code Byte} object
205 * equal to the value of:
206 *
207 * <blockquote>
208 * {@code new Byte(Byte.parseByte(s, radix))}
209 * </blockquote>
210 *
211 * @param s the string to be parsed
212 * @param radix the radix to be used in interpreting {@code s}
213 * @return a {@code Byte} object holding the value
214 * represented by the string argument in the
215 * specified radix.
216 * @throws NumberFormatException If the {@code String} does
217 * not contain a parsable {@code byte}.
218 */
219 public static Byte valueOf(String s, int radix)
220 throws NumberFormatException {
221 return valueOf(parseByte(s, radix));
222 }
223
224 /**
225 * Returns a {@code Byte} object holding the value
226 * given by the specified {@code String}. The argument is
227 * interpreted as representing a signed decimal {@code byte},
228 * exactly as if the argument were given to the {@link
229 * #parseByte(java.lang.String)} method. The result is a
230 * {@code Byte} object that represents the {@code byte}
231 * value specified by the string.
232 *
233 * <p> In other words, this method returns a {@code Byte} object
234 * equal to the value of:
235 *
236 * <blockquote>
237 * {@code new Byte(Byte.parseByte(s))}
238 * </blockquote>
239 *
240 * @param s the string to be parsed
241 * @return a {@code Byte} object holding the value
242 * represented by the string argument
243 * @throws NumberFormatException If the {@code String} does
244 * not contain a parsable {@code byte}.
245 */
246 public static Byte valueOf(String s) throws NumberFormatException {
247 return valueOf(s, 10);
248 }
249
250 /**
251 * Decodes a {@code String} into a {@code Byte}.
252 * Accepts decimal, hexadecimal, and octal numbers given by
253 * the following grammar:
254 *
255 * <blockquote>
256 * <dl>
257 * <dt><i>DecodableString:</i>
258 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
259 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
260 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
261 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
262 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
263 *
264 * <dt><i>Sign:</i>
265 * <dd>{@code -}
266 * <dd>{@code +}
267 * </dl>
268 * </blockquote>
269 *
270 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
271 * are as defined in section 3.10.1 of
272 * <cite>The Java™ Language Specification</cite>,
273 * except that underscores are not accepted between digits.
274 *
275 * <p>The sequence of characters following an optional
276 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
277 * "{@code #}", or leading zero) is parsed as by the {@code
278 * Byte.parseByte} method with the indicated radix (10, 16, or 8).
279 * This sequence of characters must represent a positive value or
280 * a {@link NumberFormatException} will be thrown. The result is
281 * negated if first character of the specified {@code String} is
282 * the minus sign. No whitespace characters are permitted in the
283 * {@code String}.
284 *
285 * @param nm the {@code String} to decode.
286 * @return a {@code Byte} object holding the {@code byte}
287 * value represented by {@code nm}
288 * @throws NumberFormatException if the {@code String} does not
289 * contain a parsable {@code byte}.
290 * @see java.lang.Byte#parseByte(java.lang.String, int)
291 */
292 public static Byte decode(String nm) throws NumberFormatException {
293 int i = Integer.decode(nm);
294 if (i < MIN_VALUE || i > MAX_VALUE)
295 throw new NumberFormatException(
296 "Value " + i + " out of range from input " + nm);
297 return valueOf((byte)i);
298 }
299
300 /**
301 * The value of the {@code Byte}.
302 *
303 * @serial
304 */
305 private final byte value;
306
307 /**
308 * Constructs a newly allocated {@code Byte} object that
309 * represents the specified {@code byte} value.
310 *
311 * @param value the value to be represented by the
312 * {@code Byte}.
313 *
314 * @deprecated
315 * It is rarely appropriate to use this constructor. The static factory
316 * {@link #valueOf(byte)} is generally a better choice, as it is
317 * likely to yield significantly better space and time performance.
318 */
319 @Deprecated(since="9")
320 public Byte(byte value) {
321 this.value = value;
322 }
323
324 /**
325 * Constructs a newly allocated {@code Byte} object that
326 * represents the {@code byte} value indicated by the
327 * {@code String} parameter. The string is converted to a
328 * {@code byte} value in exactly the manner used by the
329 * {@code parseByte} method for radix 10.
330 *
331 * @param s the {@code String} to be converted to a
332 * {@code Byte}
333 * @throws NumberFormatException if the {@code String}
334 * does not contain a parsable {@code byte}.
335 *
336 * @deprecated
337 * It is rarely appropriate to use this constructor.
338 * Use {@link #parseByte(String)} to convert a string to a
339 * {@code byte} primitive, or use {@link #valueOf(String)}
340 * to convert a string to a {@code Byte} object.
341 */
342 @Deprecated(since="9")
343 public Byte(String s) throws NumberFormatException {
344 this.value = parseByte(s, 10);
345 }
346
347 /**
348 * Returns the value of this {@code Byte} as a
349 * {@code byte}.
350 */
351 @HotSpotIntrinsicCandidate
352 public byte byteValue() {
353 return value;
354 }
355
356 /**
357 * Returns the value of this {@code Byte} as a {@code short} after
358 * a widening primitive conversion.
359 * @jls 5.1.2 Widening Primitive Conversion
360 */
361 public short shortValue() {
362 return (short)value;
363 }
364
365 /**
366 * Returns the value of this {@code Byte} as an {@code int} after
367 * a widening primitive conversion.
368 * @jls 5.1.2 Widening Primitive Conversion
369 */
370 public int intValue() {
371 return (int)value;
372 }
373
374 /**
375 * Returns the value of this {@code Byte} as a {@code long} after
376 * a widening primitive conversion.
377 * @jls 5.1.2 Widening Primitive Conversion
378 */
379 public long longValue() {
380 return (long)value;
381 }
382
383 /**
384 * Returns the value of this {@code Byte} as a {@code float} after
385 * a widening primitive conversion.
386 * @jls 5.1.2 Widening Primitive Conversion
387 */
388 public float floatValue() {
389 return (float)value;
390 }
391
392 /**
393 * Returns the value of this {@code Byte} as a {@code double}
394 * after a widening primitive conversion.
395 * @jls 5.1.2 Widening Primitive Conversion
396 */
397 public double doubleValue() {
398 return (double)value;
399 }
400
401 /**
402 * Returns a {@code String} object representing this
403 * {@code Byte}'s value. The value is converted to signed
404 * decimal representation and returned as a string, exactly as if
405 * the {@code byte} value were given as an argument to the
406 * {@link java.lang.Byte#toString(byte)} method.
407 *
408 * @return a string representation of the value of this object in
409 * base 10.
410 */
411 public String toString() {
412 return Integer.toString((int)value);
413 }
414
415 /**
416 * Returns a hash code for this {@code Byte}; equal to the result
417 * of invoking {@code intValue()}.
418 *
419 * @return a hash code value for this {@code Byte}
420 */
421 @Override
422 public int hashCode() {
423 return Byte.hashCode(value);
424 }
425
426 /**
427 * Returns a hash code for a {@code byte} value; compatible with
428 * {@code Byte.hashCode()}.
429 *
430 * @param value the value to hash
431 * @return a hash code value for a {@code byte} value.
432 * @since 1.8
433 */
434 public static int hashCode(byte value) {
435 return (int)value;
436 }
437
438 /**
439 * Compares this object to the specified object. The result is
440 * {@code true} if and only if the argument is not
441 * {@code null} and is a {@code Byte} object that
442 * contains the same {@code byte} value as this object.
443 *
444 * @param obj the object to compare with
445 * @return {@code true} if the objects are the same;
446 * {@code false} otherwise.
447 */
448 public boolean equals(Object obj) {
449 if (obj instanceof Byte) {
450 return value == ((Byte)obj).byteValue();
451 }
452 return false;
453 }
454
455 /**
456 * Compares two {@code Byte} objects numerically.
457 *
458 * @param anotherByte the {@code Byte} to be compared.
459 * @return the value {@code 0} if this {@code Byte} is
460 * equal to the argument {@code Byte}; a value less than
461 * {@code 0} if this {@code Byte} is numerically less
462 * than the argument {@code Byte}; and a value greater than
463 * {@code 0} if this {@code Byte} is numerically
464 * greater than the argument {@code Byte} (signed
465 * comparison).
466 * @since 1.2
467 */
468 public int compareTo(Byte anotherByte) {
469 return compare(this.value, anotherByte.value);
470 }
471
472 /**
473 * Compares two {@code byte} values numerically.
474 * The value returned is identical to what would be returned by:
475 * <pre>
476 * Byte.valueOf(x).compareTo(Byte.valueOf(y))
477 * </pre>
478 *
479 * @param x the first {@code byte} to compare
480 * @param y the second {@code byte} to compare
481 * @return the value {@code 0} if {@code x == y};
482 * a value less than {@code 0} if {@code x < y}; and
483 * a value greater than {@code 0} if {@code x > y}
484 * @since 1.7
485 */
486 public static int compare(byte x, byte y) {
487 return x - y;
488 }
489
490 /**
491 * Compares two {@code byte} values numerically treating the values
492 * as unsigned.
493 *
494 * @param x the first {@code byte} to compare
495 * @param y the second {@code byte} to compare
496 * @return the value {@code 0} if {@code x == y}; a value less
497 * than {@code 0} if {@code x < y} as unsigned values; and
498 * a value greater than {@code 0} if {@code x > y} as
499 * unsigned values
500 * @since 9
501 */
502 public static int compareUnsigned(byte x, byte y) {
503 return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y);
504 }
505
506 /**
507 * Converts the argument to an {@code int} by an unsigned
508 * conversion. In an unsigned conversion to an {@code int}, the
509 * high-order 24 bits of the {@code int} are zero and the
510 * low-order 8 bits are equal to the bits of the {@code byte} argument.
511 *
512 * Consequently, zero and positive {@code byte} values are mapped
513 * to a numerically equal {@code int} value and negative {@code
514 * byte} values are mapped to an {@code int} value equal to the
515 * input plus 2<sup>8</sup>.
516 *
517 * @param x the value to convert to an unsigned {@code int}
518 * @return the argument converted to {@code int} by an unsigned
519 * conversion
520 * @since 1.8
521 */
522 public static int toUnsignedInt(byte x) {
523 return ((int) x) & 0xff;
524 }
525
526 /**
527 * Converts the argument to a {@code long} by an unsigned
528 * conversion. In an unsigned conversion to a {@code long}, the
529 * high-order 56 bits of the {@code long} are zero and the
530 * low-order 8 bits are equal to the bits of the {@code byte} argument.
531 *
532 * Consequently, zero and positive {@code byte} values are mapped
533 * to a numerically equal {@code long} value and negative {@code
534 * byte} values are mapped to a {@code long} value equal to the
535 * input plus 2<sup>8</sup>.
536 *
537 * @param x the value to convert to an unsigned {@code long}
538 * @return the argument converted to {@code long} by an unsigned
539 * conversion
540 * @since 1.8
541 */
542 public static long toUnsignedLong(byte x) {
543 return ((long) x) & 0xffL;
544 }
545
546
547 /**
548 * The number of bits used to represent a {@code byte} value in two's
549 * complement binary form.
550 *
551 * @since 1.5
552 */
553 public static final int SIZE = 8;
554
555 /**
556 * The number of bytes used to represent a {@code byte} value in two's
557 * complement binary form.
558 *
559 * @since 1.8
560 */
561 public static final int BYTES = SIZE / Byte.SIZE;
562
563 /** use serialVersionUID from JDK 1.1. for interoperability */
564 private static final long serialVersionUID = -7183698231559129828L;
565 }