1 /*
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   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 
  30 /**
  31  *
  32  * The {@code Byte} class wraps a value of primitive type {@code byte}
  33  * in an object.  An object of type {@code Byte} contains a single
  34  * field whose type is {@code byte}.
  35  *
  36  * <p>In addition, this class provides several methods for converting
  37  * a {@code byte} to a {@code String} and a {@code String} to a {@code
  38  * byte}, as well as other constants and methods useful when dealing
  39  * with a {@code byte}.
  40  *
  41  * @author  Nakul Saraiya
  42  * @author  Joseph D. Darcy
  43  * @see     java.lang.Number
  44  * @since   1.1
  45  */
  46 public final class Byte extends Number implements Comparable<Byte> {
  47 
  48     /**
  49      * A constant holding the minimum value a {@code byte} can
  50      * have, -2<sup>7</sup>.
  51      */
  52     public static final byte   MIN_VALUE = -128;
  53 
  54     /**
  55      * A constant holding the maximum value a {@code byte} can
  56      * have, 2<sup>7</sup>-1.
  57      */
  58     public static final byte   MAX_VALUE = 127;
  59 
  60     /**
  61      * The {@code Class} instance representing the primitive type
  62      * {@code byte}.
  63      */
  64     @SuppressWarnings("unchecked")
  65     public static final Class<Byte>     TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
  66 
  67     /**
  68      * Returns a new {@code String} object representing the
  69      * specified {@code byte}. The radix is assumed to be 10.
  70      *
  71      * @param b the {@code byte} to be converted
  72      * @return the string representation of the specified {@code byte}
  73      * @see java.lang.Integer#toString(int)
  74      */
  75     public static String toString(byte b) {
  76         return Integer.toString((int)b, 10);
  77     }
  78 
  79     private static class ByteCache {
  80         private ByteCache(){}
  81 
  82         static final Byte cache[] = new Byte[-(-128) + 127 + 1];
  83 
  84         static {
  85             for(int i = 0; i < cache.length; i++)
  86                 cache[i] = new Byte((byte)(i - 128));
  87         }
  88     }
  89 
  90     /**
  91      * Returns a {@code Byte} instance representing the specified
  92      * {@code byte} value.
  93      * If a new {@code Byte} instance is not required, this method
  94      * should generally be used in preference to the constructor
  95      * {@link #Byte(byte)}, as this method is likely to yield
  96      * significantly better space and time performance since
  97      * all byte values are cached.
  98      *
  99      * @param  b a byte value.
 100      * @return a {@code Byte} instance representing {@code b}.
 101      * @since  1.5
 102      */
 103     @HotSpotIntrinsicCandidate
 104     public static Byte valueOf(byte b) {
 105         final int offset = 128;
 106         return ByteCache.cache[(int)b + offset];
 107     }
 108 
 109     /**
 110      * Parses the string argument as a signed {@code byte} in the
 111      * radix specified by the second argument. The characters in the
 112      * string must all be digits, of the specified radix (as
 113      * determined by whether {@link java.lang.Character#digit(char,
 114      * int)} returns a nonnegative value) except that the first
 115      * character may be an ASCII minus sign {@code '-'}
 116      * ({@code '\u005Cu002D'}) to indicate a negative value or an
 117      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
 118      * indicate a positive value.  The resulting {@code byte} value is
 119      * returned.
 120      *
 121      * <p>An exception of type {@code NumberFormatException} is
 122      * thrown if any of the following situations occurs:
 123      * <ul>
 124      * <li> The first argument is {@code null} or is a string of
 125      * length zero.
 126      *
 127      * <li> The radix is either smaller than {@link
 128      * java.lang.Character#MIN_RADIX} or larger than {@link
 129      * java.lang.Character#MAX_RADIX}.
 130      *
 131      * <li> Any character of the string is not a digit of the
 132      * specified radix, except that the first character may be a minus
 133      * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
 134      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 135      * string is longer than length 1.
 136      *
 137      * <li> The value represented by the string is not a value of type
 138      * {@code byte}.
 139      * </ul>
 140      *
 141      * @param s         the {@code String} containing the
 142      *                  {@code byte}
 143      *                  representation to be parsed
 144      * @param radix     the radix to be used while parsing {@code s}
 145      * @return          the {@code byte} value represented by the string
 146      *                   argument in the specified radix
 147      * @throws          NumberFormatException If the string does
 148      *                  not contain a parsable {@code byte}.
 149      */
 150     public static byte parseByte(String s, int radix)
 151         throws NumberFormatException {
 152         int i = Integer.parseInt(s, radix);
 153         if (i < MIN_VALUE || i > MAX_VALUE)
 154             throw new NumberFormatException(
 155                 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
 156         return (byte)i;
 157     }
 158 
 159     /**
 160      * Parses the string argument as a signed decimal {@code
 161      * byte}. The characters in the string must all be decimal digits,
 162      * except that the first character may be an ASCII minus sign
 163      * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
 164      * value or an ASCII plus sign {@code '+'}
 165      * ({@code '\u005Cu002B'}) to indicate a positive value. The
 166      * resulting {@code byte} value is returned, exactly as if the
 167      * argument and the radix 10 were given as arguments to the {@link
 168      * #parseByte(java.lang.String, int)} method.
 169      *
 170      * @param s         a {@code String} containing the
 171      *                  {@code byte} representation to be parsed
 172      * @return          the {@code byte} value represented by the
 173      *                  argument in decimal
 174      * @throws          NumberFormatException if the string does not
 175      *                  contain a parsable {@code byte}.
 176      */
 177     public static byte parseByte(String s) throws NumberFormatException {
 178         return parseByte(s, 10);
 179     }
 180 
 181     /**
 182      * Returns a {@code Byte} object holding the value
 183      * extracted from the specified {@code String} when parsed
 184      * with the radix given by the second argument. The first argument
 185      * is interpreted as representing a signed {@code byte} in
 186      * the radix specified by the second argument, exactly as if the
 187      * argument were given to the {@link #parseByte(java.lang.String,
 188      * int)} method. The result is a {@code Byte} object that
 189      * represents the {@code byte} value specified by the string.
 190      *
 191      * <p> In other words, this method returns a {@code Byte} object
 192      * equal to the value of:
 193      *
 194      * <blockquote>
 195      * {@code new Byte(Byte.parseByte(s, radix))}
 196      * </blockquote>
 197      *
 198      * @param s         the string to be parsed
 199      * @param radix     the radix to be used in interpreting {@code s}
 200      * @return          a {@code Byte} object holding the value
 201      *                  represented by the string argument in the
 202      *                  specified radix.
 203      * @throws          NumberFormatException If the {@code String} does
 204      *                  not contain a parsable {@code byte}.
 205      */
 206     public static Byte valueOf(String s, int radix)
 207         throws NumberFormatException {
 208         return valueOf(parseByte(s, radix));
 209     }
 210 
 211     /**
 212      * Returns a {@code Byte} object holding the value
 213      * given by the specified {@code String}. The argument is
 214      * interpreted as representing a signed decimal {@code byte},
 215      * exactly as if the argument were given to the {@link
 216      * #parseByte(java.lang.String)} method. The result is a
 217      * {@code Byte} object that represents the {@code byte}
 218      * value specified by the string.
 219      *
 220      * <p> In other words, this method returns a {@code Byte} object
 221      * equal to the value of:
 222      *
 223      * <blockquote>
 224      * {@code new Byte(Byte.parseByte(s))}
 225      * </blockquote>
 226      *
 227      * @param s         the string to be parsed
 228      * @return          a {@code Byte} object holding the value
 229      *                  represented by the string argument
 230      * @throws          NumberFormatException If the {@code String} does
 231      *                  not contain a parsable {@code byte}.
 232      */
 233     public static Byte valueOf(String s) throws NumberFormatException {
 234         return valueOf(s, 10);
 235     }
 236 
 237     /**
 238      * Decodes a {@code String} into a {@code Byte}.
 239      * Accepts decimal, hexadecimal, and octal numbers given by
 240      * the following grammar:
 241      *
 242      * <blockquote>
 243      * <dl>
 244      * <dt><i>DecodableString:</i>
 245      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
 246      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
 247      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
 248      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
 249      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
 250      *
 251      * <dt><i>Sign:</i>
 252      * <dd>{@code -}
 253      * <dd>{@code +}
 254      * </dl>
 255      * </blockquote>
 256      *
 257      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
 258      * are as defined in section 3.10.1 of
 259      * <cite>The Java&trade; Language Specification</cite>,
 260      * except that underscores are not accepted between digits.
 261      *
 262      * <p>The sequence of characters following an optional
 263      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
 264      * "{@code #}", or leading zero) is parsed as by the {@code
 265      * Byte.parseByte} method with the indicated radix (10, 16, or 8).
 266      * This sequence of characters must represent a positive value or
 267      * a {@link NumberFormatException} will be thrown.  The result is
 268      * negated if first character of the specified {@code String} is
 269      * the minus sign.  No whitespace characters are permitted in the
 270      * {@code String}.
 271      *
 272      * @param     nm the {@code String} to decode.
 273      * @return   a {@code Byte} object holding the {@code byte}
 274      *          value represented by {@code nm}
 275      * @throws  NumberFormatException  if the {@code String} does not
 276      *            contain a parsable {@code byte}.
 277      * @see java.lang.Byte#parseByte(java.lang.String, int)
 278      */
 279     public static Byte decode(String nm) throws NumberFormatException {
 280         int i = Integer.decode(nm);
 281         if (i < MIN_VALUE || i > MAX_VALUE)
 282             throw new NumberFormatException(
 283                     "Value " + i + " out of range from input " + nm);
 284         return valueOf((byte)i);
 285     }
 286 
 287     /**
 288      * The value of the {@code Byte}.
 289      *
 290      * @serial
 291      */
 292     private final byte value;
 293 
 294     /**
 295      * Constructs a newly allocated {@code Byte} object that
 296      * represents the specified {@code byte} value.
 297      *
 298      * @param value     the value to be represented by the
 299      *                  {@code Byte}.
 300      */
 301     public Byte(byte value) {
 302         this.value = value;
 303     }
 304 
 305     /**
 306      * Constructs a newly allocated {@code Byte} object that
 307      * represents the {@code byte} value indicated by the
 308      * {@code String} parameter. The string is converted to a
 309      * {@code byte} value in exactly the manner used by the
 310      * {@code parseByte} method for radix 10.
 311      *
 312      * @param s         the {@code String} to be converted to a
 313      *                  {@code Byte}
 314      * @throws           NumberFormatException If the {@code String}
 315      *                  does not contain a parsable {@code byte}.
 316      * @see        java.lang.Byte#parseByte(java.lang.String, int)
 317      */
 318     public Byte(String s) throws NumberFormatException {
 319         this.value = parseByte(s, 10);
 320     }
 321 
 322     /**
 323      * Returns the value of this {@code Byte} as a
 324      * {@code byte}.
 325      */
 326     @HotSpotIntrinsicCandidate
 327     public byte byteValue() {
 328         return value;
 329     }
 330 
 331     /**
 332      * Returns the value of this {@code Byte} as a {@code short} after
 333      * a widening primitive conversion.
 334      * @jls 5.1.2 Widening Primitive Conversions
 335      */
 336     public short shortValue() {
 337         return (short)value;
 338     }
 339 
 340     /**
 341      * Returns the value of this {@code Byte} as an {@code int} after
 342      * a widening primitive conversion.
 343      * @jls 5.1.2 Widening Primitive Conversions
 344      */
 345     public int intValue() {
 346         return (int)value;
 347     }
 348 
 349     /**
 350      * Returns the value of this {@code Byte} as a {@code long} after
 351      * a widening primitive conversion.
 352      * @jls 5.1.2 Widening Primitive Conversions
 353      */
 354     public long longValue() {
 355         return (long)value;
 356     }
 357 
 358     /**
 359      * Returns the value of this {@code Byte} as a {@code float} after
 360      * a widening primitive conversion.
 361      * @jls 5.1.2 Widening Primitive Conversions
 362      */
 363     public float floatValue() {
 364         return (float)value;
 365     }
 366 
 367     /**
 368      * Returns the value of this {@code Byte} as a {@code double}
 369      * after a widening primitive conversion.
 370      * @jls 5.1.2 Widening Primitive Conversions
 371      */
 372     public double doubleValue() {
 373         return (double)value;
 374     }
 375 
 376     /**
 377      * Returns a {@code String} object representing this
 378      * {@code Byte}'s value.  The value is converted to signed
 379      * decimal representation and returned as a string, exactly as if
 380      * the {@code byte} value were given as an argument to the
 381      * {@link java.lang.Byte#toString(byte)} method.
 382      *
 383      * @return  a string representation of the value of this object in
 384      *          base&nbsp;10.
 385      */
 386     public String toString() {
 387         return Integer.toString((int)value);
 388     }
 389 
 390     /**
 391      * Returns a hash code for this {@code Byte}; equal to the result
 392      * of invoking {@code intValue()}.
 393      *
 394      * @return a hash code value for this {@code Byte}
 395      */
 396     @Override
 397     public int hashCode() {
 398         return Byte.hashCode(value);
 399     }
 400 
 401     /**
 402      * Returns a hash code for a {@code byte} value; compatible with
 403      * {@code Byte.hashCode()}.
 404      *
 405      * @param value the value to hash
 406      * @return a hash code value for a {@code byte} value.
 407      * @since 1.8
 408      */
 409     public static int hashCode(byte value) {
 410         return (int)value;
 411     }
 412 
 413     /**
 414      * Compares this object to the specified object.  The result is
 415      * {@code true} if and only if the argument is not
 416      * {@code null} and is a {@code Byte} object that
 417      * contains the same {@code byte} value as this object.
 418      *
 419      * @param obj       the object to compare with
 420      * @return          {@code true} if the objects are the same;
 421      *                  {@code false} otherwise.
 422      */
 423     public boolean equals(Object obj) {
 424         if (obj instanceof Byte) {
 425             return value == ((Byte)obj).byteValue();
 426         }
 427         return false;
 428     }
 429 
 430     /**
 431      * Compares two {@code Byte} objects numerically.
 432      *
 433      * @param   anotherByte   the {@code Byte} to be compared.
 434      * @return  the value {@code 0} if this {@code Byte} is
 435      *          equal to the argument {@code Byte}; a value less than
 436      *          {@code 0} if this {@code Byte} is numerically less
 437      *          than the argument {@code Byte}; and a value greater than
 438      *           {@code 0} if this {@code Byte} is numerically
 439      *           greater than the argument {@code Byte} (signed
 440      *           comparison).
 441      * @since   1.2
 442      */
 443     public int compareTo(Byte anotherByte) {
 444         return compare(this.value, anotherByte.value);
 445     }
 446 
 447     /**
 448      * Compares two {@code byte} values numerically.
 449      * The value returned is identical to what would be returned by:
 450      * <pre>
 451      *    Byte.valueOf(x).compareTo(Byte.valueOf(y))
 452      * </pre>
 453      *
 454      * @param  x the first {@code byte} to compare
 455      * @param  y the second {@code byte} to compare
 456      * @return the value {@code 0} if {@code x == y};
 457      *         a value less than {@code 0} if {@code x < y}; and
 458      *         a value greater than {@code 0} if {@code x > y}
 459      * @since 1.7
 460      */
 461     public static int compare(byte x, byte y) {
 462         return x - y;
 463     }
 464 
 465     /**
 466      * Compares two {@code byte} values numerically treating the values
 467      * as unsigned.
 468      *
 469      * @param  x the first {@code byte} to compare
 470      * @param  y the second {@code byte} to compare
 471      * @return the value {@code 0} if {@code x == y}; a value less
 472      *         than {@code 0} if {@code x < y} as unsigned values; and
 473      *         a value greater than {@code 0} if {@code x > y} as
 474      *         unsigned values
 475      * @since 9
 476      */
 477     public static int compareUnsigned(byte x, byte y) {
 478         return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y);
 479     }
 480 
 481     /**
 482      * Converts the argument to an {@code int} by an unsigned
 483      * conversion.  In an unsigned conversion to an {@code int}, the
 484      * high-order 24 bits of the {@code int} 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 int} value and negative {@code
 489      * byte} values are mapped to an {@code int} value equal to the
 490      * input plus 2<sup>8</sup>.
 491      *
 492      * @param  x the value to convert to an unsigned {@code int}
 493      * @return the argument converted to {@code int} by an unsigned
 494      *         conversion
 495      * @since 1.8
 496      */
 497     public static int toUnsignedInt(byte x) {
 498         return ((int) x) & 0xff;
 499     }
 500 
 501     /**
 502      * Converts the argument to a {@code long} by an unsigned
 503      * conversion.  In an unsigned conversion to a {@code long}, the
 504      * high-order 56 bits of the {@code long} are zero and the
 505      * low-order 8 bits are equal to the bits of the {@code byte} argument.
 506      *
 507      * Consequently, zero and positive {@code byte} values are mapped
 508      * to a numerically equal {@code long} value and negative {@code
 509      * byte} values are mapped to a {@code long} value equal to the
 510      * input plus 2<sup>8</sup>.
 511      *
 512      * @param  x the value to convert to an unsigned {@code long}
 513      * @return the argument converted to {@code long} by an unsigned
 514      *         conversion
 515      * @since 1.8
 516      */
 517     public static long toUnsignedLong(byte x) {
 518         return ((long) x) & 0xffL;
 519     }
 520 
 521 
 522     /**
 523      * The number of bits used to represent a {@code byte} value in two's
 524      * complement binary form.
 525      *
 526      * @since 1.5
 527      */
 528     public static final int SIZE = 8;
 529 
 530     /**
 531      * The number of bytes used to represent a {@code byte} value in two's
 532      * complement binary form.
 533      *
 534      * @since 1.8
 535      */
 536     public static final int BYTES = SIZE / Byte.SIZE;
 537 
 538     /** use serialVersionUID from JDK 1.1. for interoperability */
 539     private static final long serialVersionUID = -7183698231559129828L;
 540 }