1 /*
   2  * Copyright (c) 1996, 2012, 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      */
  73     public static String toString(byte b) {
  74         return Integer.toString((int)b, 10);
  75     }
  76 
  77     private static class 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      */
 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>'&#92;u002D'</code>) to indicate a negative value or an
 114      * ASCII plus sign {@code '+'} (<code>'&#92;u002B'</code>) 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>'&#92;u002D'</code>) or plus sign
 131      * {@code '+'} (<code>'&#92;u002B'</code>) 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      */
 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>'&#92;u002D'</code>) to indicate a negative
 161      * value or an ASCII plus sign {@code '+'}
 162      * (<code>'&#92;u002B'</code>) 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      */
 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      */
 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      */
 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      * <p>
 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&trade; 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      */
 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      */
 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      */
 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      */
 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      */
 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      */
 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      */
 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      */
 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      */
 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&nbsp;10.
 381      */
 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     public int hashCode() {
 393         return (int)value;
 394     }
 395 
 396     /**
 397      * Compares this object to the specified object.  The result is
 398      * {@code true} if and only if the argument is not
 399      * {@code null} and is a {@code Byte} object that
 400      * contains the same {@code byte} value as this object.
 401      *
 402      * @param obj       the object to compare with
 403      * @return          {@code true} if the objects are the same;
 404      *                  {@code false} otherwise.
 405      */
 406     public boolean equals(Object obj) {
 407         if (obj instanceof Byte) {
 408             return value == ((Byte)obj).byteValue();
 409         }
 410         return false;
 411     }
 412 
 413     /**
 414      * Compares two {@code Byte} objects numerically.
 415      *
 416      * @param   anotherByte   the {@code Byte} to be compared.
 417      * @return  the value {@code 0} if this {@code Byte} is
 418      *          equal to the argument {@code Byte}; a value less than
 419      *          {@code 0} if this {@code Byte} is numerically less
 420      *          than the argument {@code Byte}; and a value greater than
 421      *           {@code 0} if this {@code Byte} is numerically
 422      *           greater than the argument {@code Byte} (signed
 423      *           comparison).
 424      * @since   1.2
 425      */
 426     public int compareTo(Byte anotherByte) {
 427         return compare(this.value, anotherByte.value);
 428     }
 429 
 430     /**
 431      * Compares two {@code byte} values numerically.
 432      * The value returned is identical to what would be returned by:
 433      * <pre>
 434      *    Byte.valueOf(x).compareTo(Byte.valueOf(y))
 435      * </pre>
 436      *
 437      * @param  x the first {@code byte} to compare
 438      * @param  y the second {@code byte} to compare
 439      * @return the value {@code 0} if {@code x == y};
 440      *         a value less than {@code 0} if {@code x < y}; and
 441      *         a value greater than {@code 0} if {@code x > y}
 442      * @since 1.7
 443      */
 444     public static int compare(byte x, byte y) {
 445         return x - y;
 446     }
 447 
 448     /**
 449      * Converts the argument to an {@code int} by an unsigned
 450      * conversion.  In an unsigned conversion to an {@code int}, the
 451      * high-order 24 bits of the {@code int} are zero and the
 452      * low-order 8 bits are equal to the bits of the {@code byte} argument.
 453      *
 454      * @return the argument converted to {@code int} by an unsigned
 455      *         conversion
 456      * @param  x the value to convert to an unsigned {@code int}
 457      * @since 1.8
 458      */
 459     public static int toUnsignedInt(byte x) {
 460         return ((int) x) & 0xff;
 461     }
 462 
 463     /**
 464      * Converts the argument to a {@code long} by an unsigned
 465      * conversion.  In an unsigned conversion to a {@code long}, the
 466      * high-order 56 bits of the {@code long} are zero and the
 467      * low-order 8 bits are equal to the bits of the {@code byte} argument.
 468      *
 469      * @return the argument converted to {@code long} by an unsigned
 470      *         conversion
 471      * @param  x the value to convert to an unsigned {@code long}
 472      * @since 1.8
 473      */
 474     public static long toUnsignedLong(byte x) {
 475         return ((long) x) & 0xffL;
 476     }
 477 
 478 
 479     /**
 480      * The number of bits used to represent a {@code byte} value in two's
 481      * complement binary form.
 482      *
 483      * @since 1.5
 484      */
 485     public static final int SIZE = 8;
 486 
 487     /** use serialVersionUID from JDK 1.1. for interoperability */
 488     private static final long serialVersionUID = -7183698231559129828L;
 489 }