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