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 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 since 94 * all byte values are cached. 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 valueOf(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 as defined in section 3.10.1 of 255 * <cite>The Java™ Language Specification</cite>, 256 * except that underscores are not accepted between digits. 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 valueOf((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 {@code short} after 328 * a widening primitive conversion. 329 * @jls 5.1.2 Widening Primitive Conversions 330 */ 331 public short shortValue() { 332 return (short)value; 333 } 334 335 /** 336 * Returns the value of this {@code Byte} as an {@code int} after 337 * a widening primitive conversion. 338 * @jls 5.1.2 Widening Primitive Conversions 339 */ 340 public int intValue() { 341 return (int)value; 342 } 343 344 /** 345 * Returns the value of this {@code Byte} as a {@code long} after 346 * a widening primitive conversion. 347 * @jls 5.1.2 Widening Primitive Conversions 348 */ 349 public long longValue() { 350 return (long)value; 351 } 352 353 /** 354 * Returns the value of this {@code Byte} as a {@code float} after 355 * a widening primitive conversion. 356 * @jls 5.1.2 Widening Primitive Conversions 357 */ 358 public float floatValue() { 359 return (float)value; 360 } 361 362 /** 363 * Returns the value of this {@code Byte} as a {@code double} 364 * after a widening primitive conversion. 365 * @jls 5.1.2 Widening Primitive Conversions 366 */ 367 public double doubleValue() { 368 return (double)value; 369 } 370 371 /** 372 * Returns a {@code String} object representing this 373 * {@code Byte}'s value. The value is converted to signed 374 * decimal representation and returned as a string, exactly as if 375 * the {@code byte} value were given as an argument to the 376 * {@link java.lang.Byte#toString(byte)} method. 377 * 378 * @return a string representation of the value of this object in 379 * base 10. 380 */ 381 public String toString() { 382 return Integer.toString((int)value); 383 } 384 385 /** 386 * Returns a hash code for this {@code Byte}; equal to the result 387 * of invoking {@code intValue()}. 388 * 389 * @return a hash code value for this {@code Byte} 390 */ 391 public int hashCode() { 392 return (int)value; 393 } 394 395 /** 396 * Compares this object to the specified object. The result is 397 * {@code true} if and only if the argument is not 398 * {@code null} and is a {@code Byte} object that 399 * contains the same {@code byte} value as this object. 400 * 401 * @param obj the object to compare with 402 * @return {@code true} if the objects are the same; 403 * {@code false} otherwise. 404 */ 405 public boolean equals(Object obj) { 406 if (obj instanceof Byte) { 407 return value == ((Byte)obj).byteValue(); 408 } 409 return false; 410 } 411 412 /** 413 * Compares two {@code Byte} objects numerically. 414 * 415 * @param anotherByte the {@code Byte} to be compared. 416 * @return the value {@code 0} if this {@code Byte} is 417 * equal to the argument {@code Byte}; a value less than 418 * {@code 0} if this {@code Byte} is numerically less 419 * than the argument {@code Byte}; and a value greater than 420 * {@code 0} if this {@code Byte} is numerically 421 * greater than the argument {@code Byte} (signed 422 * comparison). 423 * @since 1.2 424 */ 425 public int compareTo(Byte anotherByte) { 426 return compare(this.value, anotherByte.value); 427 } 428 429 /** 430 * Compares two {@code byte} values numerically. 431 * The value returned is identical to what would be returned by: 432 * <pre> 433 * Byte.valueOf(x).compareTo(Byte.valueOf(y)) 434 * </pre> 435 * 436 * @param x the first {@code byte} to compare 437 * @param y the second {@code byte} to compare 438 * @return the value {@code 0} if {@code x == y}; 439 * a value less than {@code 0} if {@code x < y}; and 440 * a value greater than {@code 0} if {@code x > y} 441 * @since 1.7 442 */ 443 public static int compare(byte x, byte y) { 444 return x - y; 445 } 446 447 /** 448 * The number of bits used to represent a {@code byte} value in two's 449 * complement binary form. 450 * 451 * @since 1.5 452 */ 453 public static final int SIZE = 8; 454 455 /** use serialVersionUID from JDK 1.1. for interoperability */ 456 private static final long serialVersionUID = -7183698231559129828L; 457 }