1 /* 2 * Copyright (c) 1996, 2020, 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 import java.lang.constant.Constable; 32 import java.lang.constant.DynamicConstantDesc; 33 import java.util.Optional; 34 35 import static java.lang.constant.ConstantDescs.BSM_EXPLICIT_CAST; 36 import static java.lang.constant.ConstantDescs.CD_byte; 37 import static java.lang.constant.ConstantDescs.CD_int; 38 import static java.lang.constant.ConstantDescs.DEFAULT_NAME; 39 40 /** 41 * 42 * The {@code Byte} class wraps a value of primitive type {@code byte} 43 * in an object. An object of type {@code Byte} contains a single 44 * field whose type is {@code byte}. 45 * 46 * <p>In addition, this class provides several methods for converting 47 * a {@code byte} to a {@code String} and a {@code String} to a {@code 48 * byte}, as well as other constants and methods useful when dealing 49 * with a {@code byte}. 50 * 51 * @author Nakul Saraiya 52 * @author Joseph D. Darcy 53 * @see java.lang.Number 54 * @since 1.1 55 */ 56 public final class Byte extends Number implements Comparable<Byte>, Constable { 57 58 /** 59 * A constant holding the minimum value a {@code byte} can 60 * have, -2<sup>7</sup>. 61 */ 62 public static final byte MIN_VALUE = -128; 63 64 /** 65 * A constant holding the maximum value a {@code byte} can 66 * have, 2<sup>7</sup>-1. 67 */ 68 public static final byte MAX_VALUE = 127; 69 70 /** 71 * The {@code Class} instance representing the primitive type 72 * {@code byte}. 73 */ 74 @SuppressWarnings("unchecked") 75 public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte"); 76 77 /** 78 * Returns a new {@code String} object representing the 79 * specified {@code byte}. The radix is assumed to be 10. 80 * 81 * @param b the {@code byte} to be converted 82 * @return the string representation of the specified {@code byte} 83 * @see java.lang.Integer#toString(int) 84 */ 85 public static String toString(byte b) { 86 return Integer.toString((int)b, 10); 87 } 88 89 /** 90 * Returns an {@link Optional} containing the nominal descriptor for this 91 * instance. 92 * 93 * @return an {@link Optional} describing the {@linkplain Byte} instance 94 * @since 15 95 */ 96 @Override 97 public Optional<DynamicConstantDesc<Byte>> describeConstable() { 98 return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue())); 99 } 100 101 private static class ByteCache { 102 private ByteCache() {} 103 104 static final Byte[] cache; 105 static Byte[] archivedCache; 106 107 static { 108 final int size = -(-128) + 127 + 1; 109 110 // Load and use the archived cache if it exists 111 VM.initializeFromArchive(ByteCache.class); 112 if (archivedCache == null || archivedCache.length != size) { 113 Byte[] c = new Byte[size]; 114 byte value = (byte)-128; 115 for(int i = 0; i < size; i++) { 116 c[i] = new Byte(value++); 117 } 118 archivedCache = c; 119 } 120 cache = archivedCache; 121 } 122 } 123 124 /** 125 * Returns a {@code Byte} instance representing the specified 126 * {@code byte} value. 127 * If a new {@code Byte} instance is not required, this method 128 * should generally be used in preference to the constructor 129 * {@link #Byte(byte)}, as this method is likely to yield 130 * significantly better space and time performance since 131 * all byte values are cached. 132 * 133 * @param b a byte value. 134 * @return a {@code Byte} instance representing {@code b}. 135 * @since 1.5 136 */ 137 @HotSpotIntrinsicCandidate 138 public static Byte valueOf(byte b) { 139 final int offset = 128; 140 return ByteCache.cache[(int)b + offset]; 141 } 142 143 /** 144 * Parses the string argument as a signed {@code byte} in the 145 * radix specified by the second argument. The characters in the 146 * string must all be digits, of the specified radix (as 147 * determined by whether {@link java.lang.Character#digit(char, 148 * int)} returns a nonnegative value) except that the first 149 * character may be an ASCII minus sign {@code '-'} 150 * ({@code '\u005Cu002D'}) to indicate a negative value or an 151 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to 152 * indicate a positive value. The resulting {@code byte} value is 153 * returned. 154 * 155 * <p>An exception of type {@code NumberFormatException} is 156 * thrown if any of the following situations occurs: 157 * <ul> 158 * <li> The first argument is {@code null} or is a string of 159 * length zero. 160 * 161 * <li> The radix is either smaller than {@link 162 * java.lang.Character#MIN_RADIX} or larger than {@link 163 * java.lang.Character#MAX_RADIX}. 164 * 165 * <li> Any character of the string is not a digit of the 166 * specified radix, except that the first character may be a minus 167 * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign 168 * {@code '+'} ({@code '\u005Cu002B'}) provided that the 169 * string is longer than length 1. 170 * 171 * <li> The value represented by the string is not a value of type 172 * {@code byte}. 173 * </ul> 174 * 175 * @param s the {@code String} containing the 176 * {@code byte} 177 * representation to be parsed 178 * @param radix the radix to be used while parsing {@code s} 179 * @return the {@code byte} value represented by the string 180 * argument in the specified radix 181 * @throws NumberFormatException If the string does 182 * not contain a parsable {@code byte}. 183 */ 184 public static byte parseByte(String s, int radix) 185 throws NumberFormatException { 186 int i = Integer.parseInt(s, radix); 187 if (i < MIN_VALUE || i > MAX_VALUE) 188 throw new NumberFormatException( 189 "Value out of range. Value:\"" + s + "\" Radix:" + radix); 190 return (byte)i; 191 } 192 193 /** 194 * Parses the string argument as a signed decimal {@code 195 * byte}. The characters in the string must all be decimal digits, 196 * except that the first character may be an ASCII minus sign 197 * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative 198 * value or an ASCII plus sign {@code '+'} 199 * ({@code '\u005Cu002B'}) to indicate a positive value. The 200 * resulting {@code byte} value is returned, exactly as if the 201 * argument and the radix 10 were given as arguments to the {@link 202 * #parseByte(java.lang.String, int)} method. 203 * 204 * @param s a {@code String} containing the 205 * {@code byte} representation to be parsed 206 * @return the {@code byte} value represented by the 207 * argument in decimal 208 * @throws NumberFormatException if the string does not 209 * contain a parsable {@code byte}. 210 */ 211 public static byte parseByte(String s) throws NumberFormatException { 212 return parseByte(s, 10); 213 } 214 215 /** 216 * Returns a {@code Byte} object holding the value 217 * extracted from the specified {@code String} when parsed 218 * with the radix given by the second argument. The first argument 219 * is interpreted as representing a signed {@code byte} in 220 * the radix specified by the second argument, exactly as if the 221 * argument were given to the {@link #parseByte(java.lang.String, 222 * int)} method. The result is a {@code Byte} object that 223 * represents the {@code byte} value specified by the string. 224 * 225 * <p> In other words, this method returns a {@code Byte} object 226 * equal to the value of: 227 * 228 * <blockquote> 229 * {@code new Byte(Byte.parseByte(s, radix))} 230 * </blockquote> 231 * 232 * @param s the string to be parsed 233 * @param radix the radix to be used in interpreting {@code s} 234 * @return a {@code Byte} object holding the value 235 * represented by the string argument in the 236 * specified radix. 237 * @throws NumberFormatException If the {@code String} does 238 * not contain a parsable {@code byte}. 239 */ 240 public static Byte valueOf(String s, int radix) 241 throws NumberFormatException { 242 return valueOf(parseByte(s, radix)); 243 } 244 245 /** 246 * Returns a {@code Byte} object holding the value 247 * given by the specified {@code String}. The argument is 248 * interpreted as representing a signed decimal {@code byte}, 249 * exactly as if the argument were given to the {@link 250 * #parseByte(java.lang.String)} method. The result is a 251 * {@code Byte} object that represents the {@code byte} 252 * value specified by the string. 253 * 254 * <p> In other words, this method returns a {@code Byte} object 255 * equal to the value of: 256 * 257 * <blockquote> 258 * {@code new Byte(Byte.parseByte(s))} 259 * </blockquote> 260 * 261 * @param s the string to be parsed 262 * @return a {@code Byte} object holding the value 263 * represented by the string argument 264 * @throws NumberFormatException If the {@code String} does 265 * not contain a parsable {@code byte}. 266 */ 267 public static Byte valueOf(String s) throws NumberFormatException { 268 return valueOf(s, 10); 269 } 270 271 /** 272 * Decodes a {@code String} into a {@code Byte}. 273 * Accepts decimal, hexadecimal, and octal numbers given by 274 * the following grammar: 275 * 276 * <blockquote> 277 * <dl> 278 * <dt><i>DecodableString:</i> 279 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 280 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 281 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 282 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 283 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 284 * 285 * <dt><i>Sign:</i> 286 * <dd>{@code -} 287 * <dd>{@code +} 288 * </dl> 289 * </blockquote> 290 * 291 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 292 * are as defined in section 3.10.1 of 293 * <cite>The Java Language Specification</cite>, 294 * except that underscores are not accepted between digits. 295 * 296 * <p>The sequence of characters following an optional 297 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 298 * "{@code #}", or leading zero) is parsed as by the {@code 299 * Byte.parseByte} method with the indicated radix (10, 16, or 8). 300 * This sequence of characters must represent a positive value or 301 * a {@link NumberFormatException} will be thrown. The result is 302 * negated if first character of the specified {@code String} is 303 * the minus sign. No whitespace characters are permitted in the 304 * {@code String}. 305 * 306 * @param nm the {@code String} to decode. 307 * @return a {@code Byte} object holding the {@code byte} 308 * value represented by {@code nm} 309 * @throws NumberFormatException if the {@code String} does not 310 * contain a parsable {@code byte}. 311 * @see java.lang.Byte#parseByte(java.lang.String, int) 312 */ 313 public static Byte decode(String nm) throws NumberFormatException { 314 int i = Integer.decode(nm); 315 if (i < MIN_VALUE || i > MAX_VALUE) 316 throw new NumberFormatException( 317 "Value " + i + " out of range from input " + nm); 318 return valueOf((byte)i); 319 } 320 321 /** 322 * The value of the {@code Byte}. 323 * 324 * @serial 325 */ 326 private final byte value; 327 328 /** 329 * Constructs a newly allocated {@code Byte} object that 330 * represents the specified {@code byte} value. 331 * 332 * @param value the value to be represented by the 333 * {@code Byte}. 334 * 335 * @deprecated 336 * It is rarely appropriate to use this constructor. The static factory 337 * {@link #valueOf(byte)} is generally a better choice, as it is 338 * likely to yield significantly better space and time performance. 339 */ 340 @Deprecated(since="9") 341 public Byte(byte value) { 342 this.value = value; 343 } 344 345 /** 346 * Constructs a newly allocated {@code Byte} object that 347 * represents the {@code byte} value indicated by the 348 * {@code String} parameter. The string is converted to a 349 * {@code byte} value in exactly the manner used by the 350 * {@code parseByte} method for radix 10. 351 * 352 * @param s the {@code String} to be converted to a 353 * {@code Byte} 354 * @throws NumberFormatException if the {@code String} 355 * does not contain a parsable {@code byte}. 356 * 357 * @deprecated 358 * It is rarely appropriate to use this constructor. 359 * Use {@link #parseByte(String)} to convert a string to a 360 * {@code byte} primitive, or use {@link #valueOf(String)} 361 * to convert a string to a {@code Byte} object. 362 */ 363 @Deprecated(since="9") 364 public Byte(String s) throws NumberFormatException { 365 this.value = parseByte(s, 10); 366 } 367 368 /** 369 * Returns the value of this {@code Byte} as a 370 * {@code byte}. 371 */ 372 @HotSpotIntrinsicCandidate 373 public byte byteValue() { 374 return value; 375 } 376 377 /** 378 * Returns the value of this {@code Byte} as a {@code short} after 379 * a widening primitive conversion. 380 * @jls 5.1.2 Widening Primitive Conversion 381 */ 382 public short shortValue() { 383 return (short)value; 384 } 385 386 /** 387 * Returns the value of this {@code Byte} as an {@code int} after 388 * a widening primitive conversion. 389 * @jls 5.1.2 Widening Primitive Conversion 390 */ 391 public int intValue() { 392 return (int)value; 393 } 394 395 /** 396 * Returns the value of this {@code Byte} as a {@code long} after 397 * a widening primitive conversion. 398 * @jls 5.1.2 Widening Primitive Conversion 399 */ 400 public long longValue() { 401 return (long)value; 402 } 403 404 /** 405 * Returns the value of this {@code Byte} as a {@code float} after 406 * a widening primitive conversion. 407 * @jls 5.1.2 Widening Primitive Conversion 408 */ 409 public float floatValue() { 410 return (float)value; 411 } 412 413 /** 414 * Returns the value of this {@code Byte} as a {@code double} 415 * after a widening primitive conversion. 416 * @jls 5.1.2 Widening Primitive Conversion 417 */ 418 public double doubleValue() { 419 return (double)value; 420 } 421 422 /** 423 * Returns a {@code String} object representing this 424 * {@code Byte}'s value. The value is converted to signed 425 * decimal representation and returned as a string, exactly as if 426 * the {@code byte} value were given as an argument to the 427 * {@link java.lang.Byte#toString(byte)} method. 428 * 429 * @return a string representation of the value of this object in 430 * base 10. 431 */ 432 public String toString() { 433 return Integer.toString((int)value); 434 } 435 436 /** 437 * Returns a hash code for this {@code Byte}; equal to the result 438 * of invoking {@code intValue()}. 439 * 440 * @return a hash code value for this {@code Byte} 441 */ 442 @Override 443 public int hashCode() { 444 return Byte.hashCode(value); 445 } 446 447 /** 448 * Returns a hash code for a {@code byte} value; compatible with 449 * {@code Byte.hashCode()}. 450 * 451 * @param value the value to hash 452 * @return a hash code value for a {@code byte} value. 453 * @since 1.8 454 */ 455 public static int hashCode(byte value) { 456 return (int)value; 457 } 458 459 /** 460 * Compares this object to the specified object. The result is 461 * {@code true} if and only if the argument is not 462 * {@code null} and is a {@code Byte} object that 463 * contains the same {@code byte} value as this object. 464 * 465 * @param obj the object to compare with 466 * @return {@code true} if the objects are the same; 467 * {@code false} otherwise. 468 */ 469 public boolean equals(Object obj) { 470 if (obj instanceof Byte) { 471 return value == ((Byte)obj).byteValue(); 472 } 473 return false; 474 } 475 476 /** 477 * Compares two {@code Byte} objects numerically. 478 * 479 * @param anotherByte the {@code Byte} to be compared. 480 * @return the value {@code 0} if this {@code Byte} is 481 * equal to the argument {@code Byte}; a value less than 482 * {@code 0} if this {@code Byte} is numerically less 483 * than the argument {@code Byte}; and a value greater than 484 * {@code 0} if this {@code Byte} is numerically 485 * greater than the argument {@code Byte} (signed 486 * comparison). 487 * @since 1.2 488 */ 489 public int compareTo(Byte anotherByte) { 490 return compare(this.value, anotherByte.value); 491 } 492 493 /** 494 * Compares two {@code byte} values numerically. 495 * The value returned is identical to what would be returned by: 496 * <pre> 497 * Byte.valueOf(x).compareTo(Byte.valueOf(y)) 498 * </pre> 499 * 500 * @param x the first {@code byte} to compare 501 * @param y the second {@code byte} to compare 502 * @return the value {@code 0} if {@code x == y}; 503 * a value less than {@code 0} if {@code x < y}; and 504 * a value greater than {@code 0} if {@code x > y} 505 * @since 1.7 506 */ 507 public static int compare(byte x, byte y) { 508 return x - y; 509 } 510 511 /** 512 * Compares two {@code byte} values numerically treating the values 513 * as unsigned. 514 * 515 * @param x the first {@code byte} to compare 516 * @param y the second {@code byte} to compare 517 * @return the value {@code 0} if {@code x == y}; a value less 518 * than {@code 0} if {@code x < y} as unsigned values; and 519 * a value greater than {@code 0} if {@code x > y} as 520 * unsigned values 521 * @since 9 522 */ 523 public static int compareUnsigned(byte x, byte y) { 524 return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y); 525 } 526 527 /** 528 * Converts the argument to an {@code int} by an unsigned 529 * conversion. In an unsigned conversion to an {@code int}, the 530 * high-order 24 bits of the {@code int} are zero and the 531 * low-order 8 bits are equal to the bits of the {@code byte} argument. 532 * 533 * Consequently, zero and positive {@code byte} values are mapped 534 * to a numerically equal {@code int} value and negative {@code 535 * byte} values are mapped to an {@code int} value equal to the 536 * input plus 2<sup>8</sup>. 537 * 538 * @param x the value to convert to an unsigned {@code int} 539 * @return the argument converted to {@code int} by an unsigned 540 * conversion 541 * @since 1.8 542 */ 543 public static int toUnsignedInt(byte x) { 544 return ((int) x) & 0xff; 545 } 546 547 /** 548 * Converts the argument to a {@code long} by an unsigned 549 * conversion. In an unsigned conversion to a {@code long}, the 550 * high-order 56 bits of the {@code long} are zero and the 551 * low-order 8 bits are equal to the bits of the {@code byte} argument. 552 * 553 * Consequently, zero and positive {@code byte} values are mapped 554 * to a numerically equal {@code long} value and negative {@code 555 * byte} values are mapped to a {@code long} value equal to the 556 * input plus 2<sup>8</sup>. 557 * 558 * @param x the value to convert to an unsigned {@code long} 559 * @return the argument converted to {@code long} by an unsigned 560 * conversion 561 * @since 1.8 562 */ 563 public static long toUnsignedLong(byte x) { 564 return ((long) x) & 0xffL; 565 } 566 567 568 /** 569 * The number of bits used to represent a {@code byte} value in two's 570 * complement binary form. 571 * 572 * @since 1.5 573 */ 574 public static final int SIZE = 8; 575 576 /** 577 * The number of bytes used to represent a {@code byte} value in two's 578 * complement binary form. 579 * 580 * @since 1.8 581 */ 582 public static final int BYTES = SIZE / Byte.SIZE; 583 584 /** use serialVersionUID from JDK 1.1. for interoperability */ 585 @java.io.Serial 586 private static final long serialVersionUID = -7183698231559129828L; 587 }