1 /*
2 * Copyright 1996-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any 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 new {@code String} object representing the
66 * specified {@code byte}. The radix is assumed to be 10.
67 *
68 * @param b the {@code byte} to be converted
69 * @return the string representation of the specified {@code byte}
70 * @see java.lang.Integer#toString(int)
71 */
72 public static String toString(byte b) {
73 return Integer.toString((int)b, 10);
74 }
75
76 private static class ByteCache {
77 private ByteCache(){}
78
79 static final Byte cache[] = new Byte[-(-128) + 127 + 1];
80
81 static {
82 for(int i = 0; i < cache.length; i++)
83 cache[i] = new Byte((byte)(i - 128));
84 }
85 }
86
87 /**
88 * Returns a {@code Byte} instance representing the specified
89 * {@code byte} value.
90 * If a new {@code Byte} instance is not required, this method
91 * should generally be used in preference to the constructor
92 * {@link #Byte(byte)}, as this method is likely to yield
93 * significantly better space and time performance by caching
94 * frequently requested values.
95 *
96 * @param b a byte value.
97 * @return a {@code Byte} instance representing {@code b}.
98 * @since 1.5
99 */
100 public static Byte valueOf(byte b) {
101 final int offset = 128;
102 return ByteCache.cache[(int)b + offset];
103 }
104
105 /**
106 * Parses the string argument as a signed {@code byte} in the
107 * radix specified by the second argument. The characters in the
108 * string must all be digits, of the specified radix (as
109 * determined by whether {@link java.lang.Character#digit(char,
110 * int)} returns a nonnegative value) except that the first
111 * character may be an ASCII minus sign {@code '-'}
112 * (<code>'\u002D'</code>) to indicate a negative value or an
113 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to
114 * indicate a positive value. The resulting {@code byte} value is
115 * returned.
116 *
117 * <p>An exception of type {@code NumberFormatException} is
118 * thrown if any of the following situations occurs:
119 * <ul>
120 * <li> The first argument is {@code null} or is a string of
121 * length zero.
122 *
123 * <li> The radix is either smaller than {@link
124 * java.lang.Character#MIN_RADIX} or larger than {@link
125 * java.lang.Character#MAX_RADIX}.
126 *
127 * <li> Any character of the string is not a digit of the
128 * specified radix, except that the first character may be a minus
129 * sign {@code '-'} (<code>'\u002D'</code>) or plus sign
130 * {@code '+'} (<code>'\u002B'</code>) provided that the
131 * string is longer than length 1.
132 *
133 * <li> The value represented by the string is not a value of type
134 * {@code byte}.
135 * </ul>
136 *
137 * @param s the {@code String} containing the
138 * {@code byte}
139 * representation to be parsed
140 * @param radix the radix to be used while parsing {@code s}
141 * @return the {@code byte} value represented by the string
142 * argument in the specified radix
143 * @throws NumberFormatException If the string does
144 * not contain a parsable {@code byte}.
145 */
146 public static byte parseByte(String s, int radix)
147 throws NumberFormatException {
148 int i = Integer.parseInt(s, radix);
149 if (i < MIN_VALUE || i > MAX_VALUE)
150 throw new NumberFormatException(
151 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
152 return (byte)i;
153 }
154
155 /**
156 * Parses the string argument as a signed decimal {@code
157 * byte}. The characters in the string must all be decimal digits,
158 * except that the first character may be an ASCII minus sign
159 * {@code '-'} (<code>'\u002D'</code>) to indicate a negative
160 * value or an ASCII plus sign {@code '+'}
161 * (<code>'\u002B'</code>) to indicate a positive value. The
162 * resulting {@code byte} value is returned, exactly as if the
163 * argument and the radix 10 were given as arguments to the {@link
164 * #parseByte(java.lang.String, int)} method.
165 *
166 * @param s a {@code String} containing the
167 * {@code byte} representation to be parsed
168 * @return the {@code byte} value represented by the
169 * argument in decimal
170 * @throws NumberFormatException if the string does not
171 * contain a parsable {@code byte}.
172 */
173 public static byte parseByte(String s) throws NumberFormatException {
174 return parseByte(s, 10);
175 }
176
177 /**
178 * Returns a {@code Byte} object holding the value
179 * extracted from the specified {@code String} when parsed
180 * with the radix given by the second argument. The first argument
181 * is interpreted as representing a signed {@code byte} in
182 * the radix specified by the second argument, exactly as if the
183 * argument were given to the {@link #parseByte(java.lang.String,
184 * int)} method. The result is a {@code Byte} object that
185 * represents the {@code byte} value specified by the string.
186 *
187 * <p> In other words, this method returns a {@code Byte} object
188 * equal to the value of:
189 *
190 * <blockquote>
191 * {@code new Byte(Byte.parseByte(s, radix))}
192 * </blockquote>
193 *
194 * @param s the string to be parsed
195 * @param radix the radix to be used in interpreting {@code s}
196 * @return a {@code Byte} object holding the value
197 * represented by the string argument in the
198 * specified radix.
199 * @throws NumberFormatException If the {@code String} does
200 * not contain a parsable {@code byte}.
201 */
202 public static Byte valueOf(String s, int radix)
203 throws NumberFormatException {
204 return new Byte(parseByte(s, radix));
205 }
206
207 /**
208 * Returns a {@code Byte} object holding the value
209 * given by the specified {@code String}. The argument is
210 * interpreted as representing a signed decimal {@code byte},
211 * exactly as if the argument were given to the {@link
212 * #parseByte(java.lang.String)} method. The result is a
213 * {@code Byte} object that represents the {@code byte}
214 * value specified by the string.
215 *
216 * <p> In other words, this method returns a {@code Byte} object
217 * equal to the value of:
218 *
219 * <blockquote>
220 * {@code new Byte(Byte.parseByte(s))}
221 * </blockquote>
222 *
223 * @param s the string to be parsed
224 * @return a {@code Byte} object holding the value
225 * represented by the string argument
226 * @throws NumberFormatException If the {@code String} does
227 * not contain a parsable {@code byte}.
228 */
229 public static Byte valueOf(String s) throws NumberFormatException {
230 return valueOf(s, 10);
231 }
232
233 /**
234 * Decodes a {@code String} into a {@code Byte}.
235 * Accepts decimal, hexadecimal, and octal numbers given by
236 * the following grammar:
237 *
238 * <blockquote>
239 * <dl>
240 * <dt><i>DecodableString:</i>
241 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
242 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
243 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
244 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
245 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
246 * <p>
247 * <dt><i>Sign:</i>
248 * <dd>{@code -}
249 * <dd>{@code +}
250 * </dl>
251 * </blockquote>
252 *
253 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
254 * are defined in <a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">§3.10.1</a>
255 * of the <a href="http://java.sun.com/docs/books/jls/html/">Java
256 * Language Specification</a>.
257 *
258 * <p>The sequence of characters following an optional
259 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
260 * "{@code #}", or leading zero) is parsed as by the {@code
261 * Byte.parseByte} method with the indicated radix (10, 16, or 8).
262 * This sequence of characters must represent a positive value or
263 * a {@link NumberFormatException} will be thrown. The result is
264 * negated if first character of the specified {@code String} is
265 * the minus sign. No whitespace characters are permitted in the
266 * {@code String}.
267 *
268 * @param nm the {@code String} to decode.
269 * @return a {@code Byte} object holding the {@code byte}
270 * value represented by {@code nm}
271 * @throws NumberFormatException if the {@code String} does not
272 * contain a parsable {@code byte}.
273 * @see java.lang.Byte#parseByte(java.lang.String, int)
274 */
275 public static Byte decode(String nm) throws NumberFormatException {
276 int i = Integer.decode(nm);
277 if (i < MIN_VALUE || i > MAX_VALUE)
278 throw new NumberFormatException(
279 "Value " + i + " out of range from input " + nm);
280 return (byte)i;
281 }
282
283 /**
284 * The value of the {@code Byte}.
285 *
286 * @serial
287 */
288 private final byte value;
289
290 /**
291 * Constructs a newly allocated {@code Byte} object that
292 * represents the specified {@code byte} value.
293 *
294 * @param value the value to be represented by the
295 * {@code Byte}.
296 */
297 public Byte(byte value) {
298 this.value = value;
299 }
300
301 /**
302 * Constructs a newly allocated {@code Byte} object that
303 * represents the {@code byte} value indicated by the
304 * {@code String} parameter. The string is converted to a
305 * {@code byte} value in exactly the manner used by the
306 * {@code parseByte} method for radix 10.
307 *
308 * @param s the {@code String} to be converted to a
309 * {@code Byte}
310 * @throws NumberFormatException If the {@code String}
311 * does not contain a parsable {@code byte}.
312 * @see java.lang.Byte#parseByte(java.lang.String, int)
313 */
314 public Byte(String s) throws NumberFormatException {
315 this.value = parseByte(s, 10);
316 }
317
318 /**
319 * Returns the value of this {@code Byte} as a
320 * {@code byte}.
321 */
322 public byte byteValue() {
323 return value;
324 }
325
326 /**
327 * Returns the value of this {@code Byte} as a
328 * {@code short}.
329 */
330 public short shortValue() {
331 return (short)value;
332 }
333
334 /**
335 * Returns the value of this {@code Byte} as an
336 * {@code int}.
337 */
338 public int intValue() {
339 return (int)value;
340 }
341
342 /**
343 * Returns the value of this {@code Byte} as a
344 * {@code long}.
345 */
346 public long longValue() {
347 return (long)value;
348 }
349
350 /**
351 * Returns the value of this {@code Byte} as a
352 * {@code float}.
353 */
354 public float floatValue() {
355 return (float)value;
356 }
357
358 /**
359 * Returns the value of this {@code Byte} as a
360 * {@code double}.
361 */
362 public double doubleValue() {
363 return (double)value;
364 }
365
366 /**
367 * Returns a {@code String} object representing this
368 * {@code Byte}'s value. The value is converted to signed
369 * decimal representation and returned as a string, exactly as if
370 * the {@code byte} value were given as an argument to the
371 * {@link java.lang.Byte#toString(byte)} method.
372 *
373 * @return a string representation of the value of this object in
374 * base 10.
375 */
376 public String toString() {
377 return String.valueOf((int)value);
378 }
379
380 /**
381 * Returns a hash code for this {@code Byte}.
382 */
383 public int hashCode() {
384 return (int)value;
385 }
386
387 /**
388 * Compares this object to the specified object. The result is
389 * {@code true} if and only if the argument is not
390 * {@code null} and is a {@code Byte} object that
391 * contains the same {@code byte} value as this object.
392 *
393 * @param obj the object to compare with
394 * @return {@code true} if the objects are the same;
395 * {@code false} otherwise.
396 */
397 public boolean equals(Object obj) {
398 if (obj instanceof Byte) {
399 return value == ((Byte)obj).byteValue();
400 }
401 return false;
402 }
403
404 /**
405 * Compares two {@code Byte} objects numerically.
406 *
407 * @param anotherByte the {@code Byte} to be compared.
408 * @return the value {@code 0} if this {@code Byte} is
409 * equal to the argument {@code Byte}; a value less than
410 * {@code 0} if this {@code Byte} is numerically less
411 * than the argument {@code Byte}; and a value greater than
412 * {@code 0} if this {@code Byte} is numerically
413 * greater than the argument {@code Byte} (signed
414 * comparison).
415 * @since 1.2
416 */
417 public int compareTo(Byte anotherByte) {
418 return this.value - anotherByte.value;
419 }
420
421 /**
422 * The number of bits used to represent a {@code byte} value in two's
423 * complement binary form.
424 *
425 * @since 1.5
426 */
427 public static final int SIZE = 8;
428
429 /** use serialVersionUID from JDK 1.1. for interoperability */
430 private static final long serialVersionUID = -7183698231559129828L;
431 }
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