1 /*
2 * Copyright (c) 1996, 2011, 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 /**
29 *
30 * The {@code Byte} class wraps a value of primitive type {@code byte}
31 * in an object. An object of type {@code Byte} contains a single
32 * field whose type is {@code byte}.
33 *
34 * <p>In addition, this class provides several methods for converting
35 * a {@code byte} to a {@code String} and a {@code String} to a {@code
36 * byte}, as well as other constants and methods useful when dealing
37 * with a {@code byte}.
38 *
39 * @author Nakul Saraiya
40 * @author Joseph D. Darcy
41 * @see java.lang.Number
42 * @since JDK1.1
43 */
44 public final class Byte extends Number implements Comparable<Byte> {
45
46 /**
47 * A constant holding the minimum value a {@code byte} can
48 * have, -2<sup>7</sup>.
49 */
50 public static final byte MIN_VALUE = -128;
51
52 /**
53 * A constant holding the maximum value a {@code byte} can
54 * have, 2<sup>7</sup>-1.
55 */
56 public static final byte MAX_VALUE = 127;
57
58 /**
59 * The {@code Class} instance representing the primitive type
60 * {@code byte}.
61 */
62 public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
63
64 /**
65 * Returns a hash code for a {@code byte} value; compatible with
66 * {@code Byte.hashCode()}.
67 *
68 * @since 1.8
69 *
70 * @return a hash code value for a {@code byte} value.
71 */
72 public static int hashCode(byte value) {
73 return (int)value;
74 }
75
76 /**
77 * Returns a new {@code String} object representing the
78 * specified {@code byte}. The radix is assumed to be 10.
79 *
80 * @param b the {@code byte} to be converted
81 * @return the string representation of the specified {@code byte}
82 * @see java.lang.Integer#toString(int)
83 */
84 public static String toString(byte b) {
85 return Integer.toString((int)b, 10);
86 }
87
88 private static class ByteCache {
89 private ByteCache(){}
90
91 static final Byte cache[] = new Byte[-(-128) + 127 + 1];
92
93 static {
94 for(int i = 0; i < cache.length; i++)
95 cache[i] = new Byte((byte)(i - 128));
96 }
97 }
98
99 /**
100 * Returns a {@code Byte} instance representing the specified
101 * {@code byte} value.
102 * If a new {@code Byte} instance is not required, this method
103 * should generally be used in preference to the constructor
104 * {@link #Byte(byte)}, as this method is likely to yield
105 * significantly better space and time performance since
106 * all byte values are cached.
107 *
108 * @param b a byte value.
109 * @return a {@code Byte} instance representing {@code b}.
110 * @since 1.5
111 */
112 public static Byte valueOf(byte b) {
113 final int offset = 128;
114 return ByteCache.cache[(int)b + offset];
115 }
116
117 /**
118 * Parses the string argument as a signed {@code byte} in the
119 * radix specified by the second argument. The characters in the
120 * string must all be digits, of the specified radix (as
121 * determined by whether {@link java.lang.Character#digit(char,
122 * int)} returns a nonnegative value) except that the first
123 * character may be an ASCII minus sign {@code '-'}
124 * (<code>'\u002D'</code>) to indicate a negative value or an
125 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to
126 * indicate a positive value. The resulting {@code byte} value is
127 * returned.
128 *
129 * <p>An exception of type {@code NumberFormatException} is
130 * thrown if any of the following situations occurs:
131 * <ul>
132 * <li> The first argument is {@code null} or is a string of
133 * length zero.
134 *
135 * <li> The radix is either smaller than {@link
136 * java.lang.Character#MIN_RADIX} or larger than {@link
137 * java.lang.Character#MAX_RADIX}.
138 *
139 * <li> Any character of the string is not a digit of the
140 * specified radix, except that the first character may be a minus
141 * sign {@code '-'} (<code>'\u002D'</code>) or plus sign
142 * {@code '+'} (<code>'\u002B'</code>) provided that the
143 * string is longer than length 1.
144 *
145 * <li> The value represented by the string is not a value of type
146 * {@code byte}.
147 * </ul>
148 *
149 * @param s the {@code String} containing the
150 * {@code byte}
151 * representation to be parsed
152 * @param radix the radix to be used while parsing {@code s}
153 * @return the {@code byte} value represented by the string
154 * argument in the specified radix
155 * @throws NumberFormatException If the string does
156 * not contain a parsable {@code byte}.
157 */
158 public static byte parseByte(String s, int radix)
159 throws NumberFormatException {
160 int i = Integer.parseInt(s, radix);
161 if (i < MIN_VALUE || i > MAX_VALUE)
162 throw new NumberFormatException(
163 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
164 return (byte)i;
165 }
166
167 /**
168 * Parses the string argument as a signed decimal {@code
169 * byte}. The characters in the string must all be decimal digits,
170 * except that the first character may be an ASCII minus sign
171 * {@code '-'} (<code>'\u002D'</code>) to indicate a negative
172 * value or an ASCII plus sign {@code '+'}
173 * (<code>'\u002B'</code>) to indicate a positive value. The
174 * resulting {@code byte} value is returned, exactly as if the
175 * argument and the radix 10 were given as arguments to the {@link
176 * #parseByte(java.lang.String, int)} method.
177 *
178 * @param s a {@code String} containing the
179 * {@code byte} representation to be parsed
180 * @return the {@code byte} value represented by the
181 * argument in decimal
182 * @throws NumberFormatException if the string does not
183 * contain a parsable {@code byte}.
184 */
185 public static byte parseByte(String s) throws NumberFormatException {
186 return parseByte(s, 10);
187 }
188
189 /**
190 * Returns a {@code Byte} object holding the value
191 * extracted from the specified {@code String} when parsed
192 * with the radix given by the second argument. The first argument
193 * is interpreted as representing a signed {@code byte} in
194 * the radix specified by the second argument, exactly as if the
195 * argument were given to the {@link #parseByte(java.lang.String,
196 * int)} method. The result is a {@code Byte} object that
197 * represents the {@code byte} value specified by the string.
198 *
199 * <p> In other words, this method returns a {@code Byte} object
200 * equal to the value of:
201 *
202 * <blockquote>
203 * {@code new Byte(Byte.parseByte(s, radix))}
204 * </blockquote>
205 *
206 * @param s the string to be parsed
207 * @param radix the radix to be used in interpreting {@code s}
208 * @return a {@code Byte} object holding the value
209 * represented by the string argument in the
210 * specified radix.
211 * @throws NumberFormatException If the {@code String} does
212 * not contain a parsable {@code byte}.
213 */
214 public static Byte valueOf(String s, int radix)
215 throws NumberFormatException {
216 return valueOf(parseByte(s, radix));
217 }
218
219 /**
220 * Returns a {@code Byte} object holding the value
221 * given by the specified {@code String}. The argument is
222 * interpreted as representing a signed decimal {@code byte},
223 * exactly as if the argument were given to the {@link
224 * #parseByte(java.lang.String)} method. The result is a
225 * {@code Byte} object that represents the {@code byte}
226 * value specified by the string.
227 *
228 * <p> In other words, this method returns a {@code Byte} object
229 * equal to the value of:
230 *
231 * <blockquote>
232 * {@code new Byte(Byte.parseByte(s))}
233 * </blockquote>
234 *
235 * @param s the string to be parsed
236 * @return a {@code Byte} object holding the value
237 * represented by the string argument
238 * @throws NumberFormatException If the {@code String} does
239 * not contain a parsable {@code byte}.
240 */
241 public static Byte valueOf(String s) throws NumberFormatException {
242 return valueOf(s, 10);
243 }
244
245 /**
246 * Decodes a {@code String} into a {@code Byte}.
247 * Accepts decimal, hexadecimal, and octal numbers given by
248 * the following grammar:
249 *
250 * <blockquote>
251 * <dl>
252 * <dt><i>DecodableString:</i>
253 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
254 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
255 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
256 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
257 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
258 * <p>
259 * <dt><i>Sign:</i>
260 * <dd>{@code -}
261 * <dd>{@code +}
262 * </dl>
263 * </blockquote>
264 *
265 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
266 * are as defined in section 3.10.1 of
267 * <cite>The Java™ Language Specification</cite>,
268 * except that underscores are not accepted between digits.
269 *
270 * <p>The sequence of characters following an optional
271 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
272 * "{@code #}", or leading zero) is parsed as by the {@code
273 * Byte.parseByte} method with the indicated radix (10, 16, or 8).
274 * This sequence of characters must represent a positive value or
275 * a {@link NumberFormatException} will be thrown. The result is
276 * negated if first character of the specified {@code String} is
277 * the minus sign. No whitespace characters are permitted in the
278 * {@code String}.
279 *
280 * @param nm the {@code String} to decode.
281 * @return a {@code Byte} object holding the {@code byte}
282 * value represented by {@code nm}
283 * @throws NumberFormatException if the {@code String} does not
284 * contain a parsable {@code byte}.
285 * @see java.lang.Byte#parseByte(java.lang.String, int)
286 */
287 public static Byte decode(String nm) throws NumberFormatException {
288 int i = Integer.decode(nm);
289 if (i < MIN_VALUE || i > MAX_VALUE)
290 throw new NumberFormatException(
291 "Value " + i + " out of range from input " + nm);
292 return valueOf((byte)i);
293 }
294
295 /**
296 * The value of the {@code Byte}.
297 *
298 * @serial
299 */
300 private final byte value;
301
302 /**
303 * Constructs a newly allocated {@code Byte} object that
304 * represents the specified {@code byte} value.
305 *
306 * @param value the value to be represented by the
307 * {@code Byte}.
308 */
309 public Byte(byte value) {
310 this.value = value;
311 }
312
313 /**
314 * Constructs a newly allocated {@code Byte} object that
315 * represents the {@code byte} value indicated by the
316 * {@code String} parameter. The string is converted to a
317 * {@code byte} value in exactly the manner used by the
318 * {@code parseByte} method for radix 10.
319 *
320 * @param s the {@code String} to be converted to a
321 * {@code Byte}
322 * @throws NumberFormatException If the {@code String}
323 * does not contain a parsable {@code byte}.
324 * @see java.lang.Byte#parseByte(java.lang.String, int)
325 */
326 public Byte(String s) throws NumberFormatException {
327 this.value = parseByte(s, 10);
328 }
329
330 /**
331 * Returns the value of this {@code Byte} as a
332 * {@code byte}.
333 */
334 public byte byteValue() {
335 return value;
336 }
337
338 /**
339 * Returns the value of this {@code Byte} as a {@code short} after
340 * a widening primitive conversion.
341 * @jls 5.1.2 Widening Primitive Conversions
342 */
343 public short shortValue() {
344 return (short)value;
345 }
346
347 /**
348 * Returns the value of this {@code Byte} as an {@code int} after
349 * a widening primitive conversion.
350 * @jls 5.1.2 Widening Primitive Conversions
351 */
352 public int intValue() {
353 return (int)value;
354 }
355
356 /**
357 * Returns the value of this {@code Byte} as a {@code long} after
358 * a widening primitive conversion.
359 * @jls 5.1.2 Widening Primitive Conversions
360 */
361 public long longValue() {
362 return (long)value;
363 }
364
365 /**
366 * Returns the value of this {@code Byte} as a {@code float} after
367 * a widening primitive conversion.
368 * @jls 5.1.2 Widening Primitive Conversions
369 */
370 public float floatValue() {
371 return (float)value;
372 }
373
374 /**
375 * Returns the value of this {@code Byte} as a {@code double}
376 * after a widening primitive conversion.
377 * @jls 5.1.2 Widening Primitive Conversions
378 */
379 public double doubleValue() {
380 return (double)value;
381 }
382
383 /**
384 * Returns a {@code String} object representing this
385 * {@code Byte}'s value. The value is converted to signed
386 * decimal representation and returned as a string, exactly as if
387 * the {@code byte} value were given as an argument to the
388 * {@link java.lang.Byte#toString(byte)} method.
389 *
390 * @return a string representation of the value of this object in
391 * base 10.
392 */
393 public String toString() {
394 return Integer.toString((int)value);
395 }
396
397 /**
398 * Returns a hash code for this {@code Byte}; equal to the result
399 * of invoking {@code intValue()}.
400 *
401 * @return a hash code value for this {@code Byte}
402 */
403 public int hashCode() {
404 return (int)value;
405 }
406
407 /**
408 * Compares this object to the specified object. The result is
409 * {@code true} if and only if the argument is not
410 * {@code null} and is a {@code Byte} object that
411 * contains the same {@code byte} value as this object.
412 *
413 * @param obj the object to compare with
414 * @return {@code true} if the objects are the same;
415 * {@code false} otherwise.
416 */
417 public boolean equals(Object obj) {
418 if (obj instanceof Byte) {
419 return value == ((Byte)obj).byteValue();
420 }
421 return false;
422 }
423
424 /**
425 * Compares two {@code Byte} objects numerically.
426 *
427 * @param anotherByte the {@code Byte} to be compared.
428 * @return the value {@code 0} if this {@code Byte} is
429 * equal to the argument {@code Byte}; a value less than
430 * {@code 0} if this {@code Byte} is numerically less
431 * than the argument {@code Byte}; and a value greater than
432 * {@code 0} if this {@code Byte} is numerically
433 * greater than the argument {@code Byte} (signed
434 * comparison).
435 * @since 1.2
436 */
437 public int compareTo(Byte anotherByte) {
438 return compare(this.value, anotherByte.value);
439 }
440
441 /**
442 * Compares two {@code byte} values numerically.
443 * The value returned is identical to what would be returned by:
444 * <pre>
445 * Byte.valueOf(x).compareTo(Byte.valueOf(y))
446 * </pre>
447 *
448 * @param x the first {@code byte} to compare
449 * @param y the second {@code byte} to compare
450 * @return the value {@code 0} if {@code x == y};
451 * a value less than {@code 0} if {@code x < y}; and
452 * a value greater than {@code 0} if {@code x > y}
453 * @since 1.7
454 */
455 public static int compare(byte x, byte y) {
456 return x - y;
457 }
458
459 /**
460 * The number of bits used to represent a {@code byte} value in two's
461 * complement binary form.
462 *
463 * @since 1.5
464 */
465 public static final int SIZE = 8;
466
467 /**
468 * The number of bytes used to represent a {@code byte} value in two's
469 * complement binary form.
470 *
471 * @since 1.8
472 */
473 public static final int BYTES = Byte.SIZE / Byte.SIZE;
474
475 /** use serialVersionUID from JDK 1.1. for interoperability */
476 private static final long serialVersionUID = -7183698231559129828L;
477 }