1 public final class Byte extends Number implements Comparable<Byte> {
2
3 /**
4 * A constant holding the minimum value a {@code byte} can
5 * have, -2<sup>7</sup>.
6 */
7 public static final byte MIN_VALUE = -128;
8
9 /**
10 * A constant holding the maximum value a {@code byte} can
11 * have, 2<sup>7</sup>-1.
12 */
13 public static final byte MAX_VALUE = 127;
14
15 /**
16 * The {@code Class} instance representing the primitive type
17 * {@code byte}.
18 */
19 @SuppressWarnings("unchecked")
20 public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
21
22 /**
23 * Returns a new {@code String} object representing the
24 * specified {@code byte}. The radix is assumed to be 10.
25 *
26 * @param b the {@code byte} to be converted
27 * @return the string representation of the specified {@code byte}
28 * @see java.lang.Integer#toString(int)
29 */
30 public static String toString(byte b) {
31 return Integer.toString((int)b, 10);
32 }
33
34 private static class ByteCache {
35 private ByteCache(){}
36
37 static final Byte cache[] = new Byte[-(-128) + 127 + 1];
38
39 static {
40 for(int i = 0; i < cache.length; i++)
41 cache[i] = new Byte((byte)(i - 128));
42 }
43 }
44
45 /**
46 * Returns a {@code Byte} instance representing the specified
47 * {@code byte} value.
48 * If a new {@code Byte} instance is not required, this method
49 * should generally be used in preference to the constructor
50 * {@link #Byte(byte)}, as this method is likely to yield
51 * significantly better space and time performance since
52 * all byte values are cached.
53 *
54 * @param b a byte value.
55 * @return a {@code Byte} instance representing {@code b}.
56 * @since 1.5
57 */
58 public static Byte valueOf(byte b) {
59 final int offset = 128;
60 return ByteCache.cache[(int)b + offset];
61 }
62
63 /**
64 * Parses the string argument as a signed {@code byte} in the
65 * radix specified by the second argument. The characters in the
66 * string must all be digits, of the specified radix (as
67 * determined by whether {@link java.lang.Character#digit(char,
68 * int)} returns a nonnegative value) except that the first
69 * character may be an ASCII minus sign {@code ‘-‘}
70 * ({@code ‘\u005Cu002D‘}) to indicate a negative value or an
71 * ASCII plus sign {@code ‘+‘} ({@code ‘\u005Cu002B‘}) to
72 * indicate a positive value. The resulting {@code byte} value is
73 * returned.
74 *
75 * <p>An exception of type {@code NumberFormatException} is
76 * thrown if any of the following situations occurs:
77 * <ul>
78 * <li> The first argument is {@code null} or is a string of
79 * length zero.
80 *
81 * <li> The radix is either smaller than {@link
82 * java.lang.Character#MIN_RADIX} or larger than {@link
83 * java.lang.Character#MAX_RADIX}.
84 *
85 * <li> Any character of the string is not a digit of the
86 * specified radix, except that the first character may be a minus
87 * sign {@code ‘-‘} ({@code ‘\u005Cu002D‘}) or plus sign
88 * {@code ‘+‘} ({@code ‘\u005Cu002B‘}) provided that the
89 * string is longer than length 1.
90 *
91 * <li> The value represented by the string is not a value of type
92 * {@code byte}.
93 * </ul>
94 *
95 * @param s the {@code String} containing the
96 * {@code byte}
97 * representation to be parsed
98 * @param radix the radix to be used while parsing {@code s}
99 * @return the {@code byte} value represented by the string
100 * argument in the specified radix
101 * @throws NumberFormatException If the string does
102 * not contain a parsable {@code byte}.
103 */
104 public static byte parseByte(String s, int radix)
105 throws NumberFormatException {
106 int i = Integer.parseInt(s, radix);
107 if (i < MIN_VALUE || i > MAX_VALUE)
108 throw new NumberFormatException(
109 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
110 return (byte)i;
111 }
112
113 /**
114 * Parses the string argument as a signed decimal {@code
115 * byte}. The characters in the string must all be decimal digits,
116 * except that the first character may be an ASCII minus sign
117 * {@code ‘-‘} ({@code ‘\u005Cu002D‘}) to indicate a negative
118 * value or an ASCII plus sign {@code ‘+‘}
119 * ({@code ‘\u005Cu002B‘}) to indicate a positive value. The
120 * resulting {@code byte} value is returned, exactly as if the
121 * argument and the radix 10 were given as arguments to the {@link
122 * #parseByte(java.lang.String, int)} method.
123 *
124 * @param s a {@code String} containing the
125 * {@code byte} representation to be parsed
126 * @return the {@code byte} value represented by the
127 * argument in decimal
128 * @throws NumberFormatException if the string does not
129 * contain a parsable {@code byte}.
130 */
131 public static byte parseByte(String s) throws NumberFormatException {
132 return parseByte(s, 10);
133 }
134
135 /**
136 * Returns a {@code Byte} object holding the value
137 * extracted from the specified {@code String} when parsed
138 * with the radix given by the second argument. The first argument
139 * is interpreted as representing a signed {@code byte} in
140 * the radix specified by the second argument, exactly as if the
141 * argument were given to the {@link #parseByte(java.lang.String,
142 * int)} method. The result is a {@code Byte} object that
143 * represents the {@code byte} value specified by the string.
144 *
145 * <p> In other words, this method returns a {@code Byte} object
146 * equal to the value of:
147 *
148 * <blockquote>
149 * {@code new Byte(Byte.parseByte(s, radix))}
150 * </blockquote>
151 *
152 * @param s the string to be parsed
153 * @param radix the radix to be used in interpreting {@code s}
154 * @return a {@code Byte} object holding the value
155 * represented by the string argument in the
156 * specified radix.
157 * @throws NumberFormatException If the {@code String} does
158 * not contain a parsable {@code byte}.
159 */
160 public static Byte valueOf(String s, int radix)
161 throws NumberFormatException {
162 return valueOf(parseByte(s, radix));
163 }
164
165 /**
166 * Returns a {@code Byte} object holding the value
167 * given by the specified {@code String}. The argument is
168 * interpreted as representing a signed decimal {@code byte},
169 * exactly as if the argument were given to the {@link
170 * #parseByte(java.lang.String)} method. The result is a
171 * {@code Byte} object that represents the {@code byte}
172 * value specified by the string.
173 *
174 * <p> In other words, this method returns a {@code Byte} object
175 * equal to the value of:
176 *
177 * <blockquote>
178 * {@code new Byte(Byte.parseByte(s))}
179 * </blockquote>
180 *
181 * @param s the string to be parsed
182 * @return a {@code Byte} object holding the value
183 * represented by the string argument
184 * @throws NumberFormatException If the {@code String} does
185 * not contain a parsable {@code byte}.
186 */
187 public static Byte valueOf(String s) throws NumberFormatException {
188 return valueOf(s, 10);
189 }
190
191 /**
192 * Decodes a {@code String} into a {@code Byte}.
193 * Accepts decimal, hexadecimal, and octal numbers given by
194 * the following grammar:
195 *
196 * <blockquote>
197 * <dl>
198 * <dt><i>DecodableString:</i>
199 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
200 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
201 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
202 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
203 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
204 *
205 * <dt><i>Sign:</i>
206 * <dd>{@code -}
207 * <dd>{@code +}
208 * </dl>
209 * </blockquote>
210 *
211 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
212 * are as defined in section 3.10.1 of
213 * <cite>The Java™ Language Specification</cite>,
214 * except that underscores are not accepted between digits.
215 *
216 * <p>The sequence of characters following an optional
217 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
218 * "{@code #}", or leading zero) is parsed as by the {@code
219 * Byte.parseByte} method with the indicated radix (10, 16, or 8).
220 * This sequence of characters must represent a positive value or
221 * a {@link NumberFormatException} will be thrown. The result is
222 * negated if first character of the specified {@code String} is
223 * the minus sign. No whitespace characters are permitted in the
224 * {@code String}.
225 *
226 * @param nm the {@code String} to decode.
227 * @return a {@code Byte} object holding the {@code byte}
228 * value represented by {@code nm}
229 * @throws NumberFormatException if the {@code String} does not
230 * contain a parsable {@code byte}.
231 * @see java.lang.Byte#parseByte(java.lang.String, int)
232 */
233 public static Byte decode(String nm) throws NumberFormatException {
234 int i = Integer.decode(nm);
235 if (i < MIN_VALUE || i > MAX_VALUE)
236 throw new NumberFormatException(
237 "Value " + i + " out of range from input " + nm);
238 return valueOf((byte)i);
239 }
240
241 /**
242 * The value of the {@code Byte}.
243 *
244 * @serial
245 */
246 private final byte value;
247
248 /**
249 * Constructs a newly allocated {@code Byte} object that
250 * represents the specified {@code byte} value.
251 *
252 * @param value the value to be represented by the
253 * {@code Byte}.
254 */
255 public Byte(byte value) {
256 this.value = value;
257 }
258
259 /**
260 * Constructs a newly allocated {@code Byte} object that
261 * represents the {@code byte} value indicated by the
262 * {@code String} parameter. The string is converted to a
263 * {@code byte} value in exactly the manner used by the
264 * {@code parseByte} method for radix 10.
265 *
266 * @param s the {@code String} to be converted to a
267 * {@code Byte}
268 * @throws NumberFormatException If the {@code String}
269 * does not contain a parsable {@code byte}.
270 * @see java.lang.Byte#parseByte(java.lang.String, int)
271 */
272 public Byte(String s) throws NumberFormatException {
273 this.value = parseByte(s, 10);
274 }
275
276 /**
277 * Returns the value of this {@code Byte} as a
278 * {@code byte}.
279 */
280 public byte byteValue() {
281 return value;
282 }
283
284 /**
285 * Returns the value of this {@code Byte} as a {@code short} after
286 * a widening primitive conversion.
287 * @jls 5.1.2 Widening Primitive Conversions
288 */
289 public short shortValue() {
290 return (short)value;
291 }
292
293 /**
294 * Returns the value of this {@code Byte} as an {@code int} after
295 * a widening primitive conversion.
296 * @jls 5.1.2 Widening Primitive Conversions
297 */
298 public int intValue() {
299 return (int)value;
300 }
301
302 /**
303 * Returns the value of this {@code Byte} as a {@code long} after
304 * a widening primitive conversion.
305 * @jls 5.1.2 Widening Primitive Conversions
306 */
307 public long longValue() {
308 return (long)value;
309 }
310
311 /**
312 * Returns the value of this {@code Byte} as a {@code float} after
313 * a widening primitive conversion.
314 * @jls 5.1.2 Widening Primitive Conversions
315 */
316 public float floatValue() {
317 return (float)value;
318 }
319
320 /**
321 * Returns the value of this {@code Byte} as a {@code double}
322 * after a widening primitive conversion.
323 * @jls 5.1.2 Widening Primitive Conversions
324 */
325 public double doubleValue() {
326 return (double)value;
327 }
328
329 /**
330 * Returns a {@code String} object representing this
331 * {@code Byte}‘s value. The value is converted to signed
332 * decimal representation and returned as a string, exactly as if
333 * the {@code byte} value were given as an argument to the
334 * {@link java.lang.Byte#toString(byte)} method.
335 *
336 * @return a string representation of the value of this object in
337 * base 10.
338 */
339 public String toString() {
340 return Integer.toString((int)value);
341 }
342
343 /**
344 * Returns a hash code for this {@code Byte}; equal to the result
345 * of invoking {@code intValue()}.
346 *
347 * @return a hash code value for this {@code Byte}
348 */
349 @Override
350 public int hashCode() {
351 return Byte.hashCode(value);
352 }
353
354 /**
355 * Returns a hash code for a {@code byte} value; compatible with
356 * {@code Byte.hashCode()}.
357 *
358 * @param value the value to hash
359 * @return a hash code value for a {@code byte} value.
360 * @since 1.8
361 */
362 public static int hashCode(byte value) {
363 return (int)value;
364 }
365
366 /**
367 * Compares this object to the specified object. The result is
368 * {@code true} if and only if the argument is not
369 * {@code null} and is a {@code Byte} object that
370 * contains the same {@code byte} value as this object.
371 *
372 * @param obj the object to compare with
373 * @return {@code true} if the objects are the same;
374 * {@code false} otherwise.
375 */
376 public boolean equals(Object obj) {
377 if (obj instanceof Byte) {
378 return value == ((Byte)obj).byteValue();
379 }
380 return false;
381 }
382
383 /**
384 * Compares two {@code Byte} objects numerically.
385 *
386 * @param anotherByte the {@code Byte} to be compared.
387 * @return the value {@code 0} if this {@code Byte} is
388 * equal to the argument {@code Byte}; a value less than
389 * {@code 0} if this {@code Byte} is numerically less
390 * than the argument {@code Byte}; and a value greater than
391 * {@code 0} if this {@code Byte} is numerically
392 * greater than the argument {@code Byte} (signed
393 * comparison).
394 * @since 1.2
395 */
396 public int compareTo(Byte anotherByte) {
397 return compare(this.value, anotherByte.value);
398 }
399
400 /**
401 * Compares two {@code byte} values numerically.
402 * The value returned is identical to what would be returned by:
403 * <pre>
404 * Byte.valueOf(x).compareTo(Byte.valueOf(y))
405 * </pre>
406 *
407 * @param x the first {@code byte} to compare
408 * @param y the second {@code byte} to compare
409 * @return the value {@code 0} if {@code x == y};
410 * a value less than {@code 0} if {@code x < y}; and
411 * a value greater than {@code 0} if {@code x > y}
412 * @since 1.7
413 */
414 public static int compare(byte x, byte y) {
415 return x - y;
416 }
417
418 /**
419 * Converts the argument to an {@code int} by an unsigned
420 * conversion. In an unsigned conversion to an {@code int}, the
421 * high-order 24 bits of the {@code int} are zero and the
422 * low-order 8 bits are equal to the bits of the {@code byte} argument.
423 *
424 * Consequently, zero and positive {@code byte} values are mapped
425 * to a numerically equal {@code int} value and negative {@code
426 * byte} values are mapped to an {@code int} value equal to the
427 * input plus 2<sup>8</sup>.
428 *
429 * @param x the value to convert to an unsigned {@code int}
430 * @return the argument converted to {@code int} by an unsigned
431 * conversion
432 * @since 1.8
433 */
434 public static int toUnsignedInt(byte x) {
435 return ((int) x) & 0xff;
436 }
437
438 /**
439 * Converts the argument to a {@code long} by an unsigned
440 * conversion. In an unsigned conversion to a {@code long}, the
441 * high-order 56 bits of the {@code long} are zero and the
442 * low-order 8 bits are equal to the bits of the {@code byte} argument.
443 *
444 * Consequently, zero and positive {@code byte} values are mapped
445 * to a numerically equal {@code long} value and negative {@code
446 * byte} values are mapped to a {@code long} value equal to the
447 * input plus 2<sup>8</sup>.
448 *
449 * @param x the value to convert to an unsigned {@code long}
450 * @return the argument converted to {@code long} by an unsigned
451 * conversion
452 * @since 1.8
453 */
454 public static long toUnsignedLong(byte x) {
455 return ((long) x) & 0xffL;
456 }
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 = SIZE / Byte.SIZE;
474
475 /** use serialVersionUID from JDK 1.1. for interoperability */
476 private static final long serialVersionUID = -7183698231559129828L;
477 }
