1 /*
   2  * Copyright (c) 1994, 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 import java.lang.annotation.Native;
  29 
  30 /**
  31  * The {@code Integer} class wraps a value of the primitive type
  32  * {@code int} in an object. An object of type {@code Integer}
  33  * contains a single field whose type is {@code int}.
  34  *
  35  * <p>In addition, this class provides several methods for converting
  36  * an {@code int} to a {@code String} and a {@code String} to an
  37  * {@code int}, as well as other constants and methods useful when
  38  * dealing with an {@code int}.
  39  *
  40  * <p>Implementation note: The implementations of the "bit twiddling"
  41  * methods (such as {@link #highestOneBit(int) highestOneBit} and
  42  * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
  43  * based on material from Henry S. Warren, Jr.'s <i>Hacker's
  44  * Delight</i>, (Addison Wesley, 2002).
  45  *
  46  * @author  Lee Boynton
  47  * @author  Arthur van Hoff
  48  * @author  Josh Bloch
  49  * @author  Joseph D. Darcy
  50  * @since JDK1.0
  51  */
  52 public final class Integer extends Number implements Comparable<Integer> {
  53     /**
  54      * A constant holding the minimum value an {@code int} can
  55      * have, -2<sup>31</sup>.
  56      */
  57     @Native public static final int   MIN_VALUE = 0x80000000;
  58 
  59     /**
  60      * A constant holding the maximum value an {@code int} can
  61      * have, 2<sup>31</sup>-1.
  62      */
  63     @Native public static final int   MAX_VALUE = 0x7fffffff;
  64 
  65     /**
  66      * The {@code Class} instance representing the primitive type
  67      * {@code int}.
  68      *
  69      * @since   JDK1.1
  70      */
  71     @SuppressWarnings("unchecked")
  72     public static final Class<Integer>  TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
  73 
  74     /**
  75      * All possible chars for representing a number as a String
  76      */
  77     final static char[] digits = {
  78         '0' , '1' , '2' , '3' , '4' , '5' ,
  79         '6' , '7' , '8' , '9' , 'a' , 'b' ,
  80         'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
  81         'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
  82         'o' , 'p' , 'q' , 'r' , 's' , 't' ,
  83         'u' , 'v' , 'w' , 'x' , 'y' , 'z'
  84     };
  85 
  86     /**
  87      * Returns a string representation of the first argument in the
  88      * radix specified by the second argument.
  89      *
  90      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
  91      * or larger than {@code Character.MAX_RADIX}, then the radix
  92      * {@code 10} is used instead.
  93      *
  94      * <p>If the first argument is negative, the first element of the
  95      * result is the ASCII minus character {@code '-'}
  96      * ({@code '\u005Cu002D'}). If the first argument is not
  97      * negative, no sign character appears in the result.
  98      *
  99      * <p>The remaining characters of the result represent the magnitude
 100      * of the first argument. If the magnitude is zero, it is
 101      * represented by a single zero character {@code '0'}
 102      * ({@code '\u005Cu0030'}); otherwise, the first character of
 103      * the representation of the magnitude will not be the zero
 104      * character.  The following ASCII characters are used as digits:
 105      *
 106      * <blockquote>
 107      *   {@code 0123456789abcdefghijklmnopqrstuvwxyz}
 108      * </blockquote>
 109      *
 110      * These are {@code '\u005Cu0030'} through
 111      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 112      * {@code '\u005Cu007A'}. If {@code radix} is
 113      * <var>N</var>, then the first <var>N</var> of these characters
 114      * are used as radix-<var>N</var> digits in the order shown. Thus,
 115      * the digits for hexadecimal (radix 16) are
 116      * {@code 0123456789abcdef}. If uppercase letters are
 117      * desired, the {@link java.lang.String#toUpperCase()} method may
 118      * be called on the result:
 119      *
 120      * <blockquote>
 121      *  {@code Integer.toString(n, 16).toUpperCase()}
 122      * </blockquote>
 123      *
 124      * @param   i       an integer to be converted to a string.
 125      * @param   radix   the radix to use in the string representation.
 126      * @return  a string representation of the argument in the specified radix.
 127      * @see     java.lang.Character#MAX_RADIX
 128      * @see     java.lang.Character#MIN_RADIX
 129      */
 130     public static String toString(int i, int radix) {
 131         if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
 132             radix = 10;
 133 
 134         /* Use the faster version */
 135         if (radix == 10) {
 136             return toString(i);
 137         }
 138 
 139         char buf[] = new char[33];
 140         boolean negative = (i < 0);
 141         int charPos = 32;
 142 
 143         if (!negative) {
 144             i = -i;
 145         }
 146 
 147         while (i <= -radix) {
 148             buf[charPos--] = digits[-(i % radix)];
 149             i = i / radix;
 150         }
 151         buf[charPos] = digits[-i];
 152 
 153         if (negative) {
 154             buf[--charPos] = '-';
 155         }
 156 
 157         return new String(buf, charPos, (33 - charPos));
 158     }
 159 
 160     /**
 161      * Returns a string representation of the first argument as an
 162      * unsigned integer value in the radix specified by the second
 163      * argument.
 164      *
 165      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
 166      * or larger than {@code Character.MAX_RADIX}, then the radix
 167      * {@code 10} is used instead.
 168      *
 169      * <p>Note that since the first argument is treated as an unsigned
 170      * value, no leading sign character is printed.
 171      *
 172      * <p>If the magnitude is zero, it is represented by a single zero
 173      * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
 174      * the first character of the representation of the magnitude will
 175      * not be the zero character.
 176      *
 177      * <p>The behavior of radixes and the characters used as digits
 178      * are the same as {@link #toString(int, int) toString}.
 179      *
 180      * @param   i       an integer to be converted to an unsigned string.
 181      * @param   radix   the radix to use in the string representation.
 182      * @return  an unsigned string representation of the argument in the specified radix.
 183      * @see     #toString(int, int)
 184      * @since 1.8
 185      */
 186     public static String toUnsignedString(int i, int radix) {
 187         return Long.toUnsignedString(toUnsignedLong(i), radix);
 188     }
 189 
 190     /**
 191      * Returns a string representation of the integer argument as an
 192      * unsigned integer in base&nbsp;16.
 193      *
 194      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 195      * if the argument is negative; otherwise, it is equal to the
 196      * argument.  This value is converted to a string of ASCII digits
 197      * in hexadecimal (base&nbsp;16) with no extra leading
 198      * {@code 0}s.
 199      *
 200      * <p>The value of the argument can be recovered from the returned
 201      * string {@code s} by calling {@link
 202      * Integer#parseUnsignedInt(String, int)
 203      * Integer.parseUnsignedInt(s, 16)}.
 204      *
 205      * <p>If the unsigned magnitude is zero, it is represented by a
 206      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 207      * otherwise, the first character of the representation of the
 208      * unsigned magnitude will not be the zero character. The
 209      * following characters are used as hexadecimal digits:
 210      *
 211      * <blockquote>
 212      *  {@code 0123456789abcdef}
 213      * </blockquote>
 214      *
 215      * These are the characters {@code '\u005Cu0030'} through
 216      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 217      * {@code '\u005Cu0066'}. If uppercase letters are
 218      * desired, the {@link java.lang.String#toUpperCase()} method may
 219      * be called on the result:
 220      *
 221      * <blockquote>
 222      *  {@code Integer.toHexString(n).toUpperCase()}
 223      * </blockquote>
 224      *
 225      * @param   i   an integer to be converted to a string.
 226      * @return  the string representation of the unsigned integer value
 227      *          represented by the argument in hexadecimal (base&nbsp;16).
 228      * @see #parseUnsignedInt(String, int)
 229      * @see #toUnsignedString(int, int)
 230      * @since   JDK1.0.2
 231      */
 232     public static String toHexString(int i) {
 233         return toUnsignedString0(i, 4);
 234     }
 235 
 236     /**
 237      * Returns a string representation of the integer argument as an
 238      * unsigned integer in base&nbsp;8.
 239      *
 240      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 241      * if the argument is negative; otherwise, it is equal to the
 242      * argument.  This value is converted to a string of ASCII digits
 243      * in octal (base&nbsp;8) with no extra leading {@code 0}s.
 244      *
 245      * <p>The value of the argument can be recovered from the returned
 246      * string {@code s} by calling {@link
 247      * Integer#parseUnsignedInt(String, int)
 248      * Integer.parseUnsignedInt(s, 8)}.
 249      *
 250      * <p>If the unsigned magnitude is zero, it is represented by a
 251      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 252      * otherwise, the first character of the representation of the
 253      * unsigned magnitude will not be the zero character. The
 254      * following characters are used as octal digits:
 255      *
 256      * <blockquote>
 257      * {@code 01234567}
 258      * </blockquote>
 259      *
 260      * These are the characters {@code '\u005Cu0030'} through
 261      * {@code '\u005Cu0037'}.
 262      *
 263      * @param   i   an integer to be converted to a string.
 264      * @return  the string representation of the unsigned integer value
 265      *          represented by the argument in octal (base&nbsp;8).
 266      * @see #parseUnsignedInt(String, int)
 267      * @see #toUnsignedString(int, int)
 268      * @since   JDK1.0.2
 269      */
 270     public static String toOctalString(int i) {
 271         return toUnsignedString0(i, 3);
 272     }
 273 
 274     /**
 275      * Returns a string representation of the integer argument as an
 276      * unsigned integer in base&nbsp;2.
 277      *
 278      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 279      * if the argument is negative; otherwise it is equal to the
 280      * argument.  This value is converted to a string of ASCII digits
 281      * in binary (base&nbsp;2) with no extra leading {@code 0}s.
 282      *
 283      * <p>The value of the argument can be recovered from the returned
 284      * string {@code s} by calling {@link
 285      * Integer#parseUnsignedInt(String, int)
 286      * Integer.parseUnsignedInt(s, 2)}.
 287      *
 288      * <p>If the unsigned magnitude is zero, it is represented by a
 289      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 290      * otherwise, the first character of the representation of the
 291      * unsigned magnitude will not be the zero character. The
 292      * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
 293      * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
 294      *
 295      * @param   i   an integer to be converted to a string.
 296      * @return  the string representation of the unsigned integer value
 297      *          represented by the argument in binary (base&nbsp;2).
 298      * @see #parseUnsignedInt(String, int)
 299      * @see #toUnsignedString(int, int)
 300      * @since   JDK1.0.2
 301      */
 302     public static String toBinaryString(int i) {
 303         return toUnsignedString0(i, 1);
 304     }
 305 
 306     /**
 307      * Convert the integer to an unsigned number.
 308      */
 309     private static String toUnsignedString0(int val, int shift) {
 310         // assert shift > 0 && shift <=5 : "Illegal shift value";
 311         int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
 312         int chars = Math.max(((mag + (shift - 1)) / shift), 1);
 313         char[] buf = new char[chars];
 314 
 315         formatUnsignedInt(val, shift, buf, 0, chars);
 316 
 317         // Use special constructor which takes over "buf".
 318         return new String(buf, true);
 319     }
 320 
 321     /**
 322      * Format a long (treated as unsigned) into a character buffer.
 323      * @param val the unsigned int to format
 324      * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
 325      * @param buf the character buffer to write to
 326      * @param offset the offset in the destination buffer to start at
 327      * @param len the number of characters to write
 328      * @return the lowest character  location used
 329      */
 330      static int formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
 331         int charPos = len;
 332         int radix = 1 << shift;
 333         int mask = radix - 1;
 334         do {
 335             buf[offset + --charPos] = Integer.digits[val & mask];
 336             val >>>= shift;
 337         } while (val != 0 && charPos > 0);
 338 
 339         return charPos;
 340     }
 341 
 342     final static char [] DigitTens = {
 343         '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
 344         '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
 345         '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
 346         '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
 347         '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
 348         '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
 349         '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
 350         '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
 351         '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
 352         '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
 353         } ;
 354 
 355     final static char [] DigitOnes = {
 356         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 357         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 358         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 359         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 360         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 361         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 362         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 363         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 364         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 365         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 366         } ;
 367 
 368         // I use the "invariant division by multiplication" trick to
 369         // accelerate Integer.toString.  In particular we want to
 370         // avoid division by 10.
 371         //
 372         // The "trick" has roughly the same performance characteristics
 373         // as the "classic" Integer.toString code on a non-JIT VM.
 374         // The trick avoids .rem and .div calls but has a longer code
 375         // path and is thus dominated by dispatch overhead.  In the
 376         // JIT case the dispatch overhead doesn't exist and the
 377         // "trick" is considerably faster than the classic code.
 378         //
 379         // RE:  Division by Invariant Integers using Multiplication
 380         //      T Gralund, P Montgomery
 381         //      ACM PLDI 1994
 382         //
 383 
 384     /**
 385      * Returns a {@code String} object representing the
 386      * specified integer. The argument is converted to signed decimal
 387      * representation and returned as a string, exactly as if the
 388      * argument and radix 10 were given as arguments to the {@link
 389      * #toString(int, int)} method.
 390      *
 391      * @param   i   an integer to be converted.
 392      * @return  a string representation of the argument in base&nbsp;10.
 393      */
 394     public static String toString(int i) {
 395         if (i == Integer.MIN_VALUE)
 396             return "-2147483648";
 397         int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
 398         char[] buf = new char[size];
 399         getChars(i, size, buf);
 400         return new String(buf, true);
 401     }
 402 
 403     /**
 404      * Returns a string representation of the argument as an unsigned
 405      * decimal value.
 406      *
 407      * The argument is converted to unsigned decimal representation
 408      * and returned as a string exactly as if the argument and radix
 409      * 10 were given as arguments to the {@link #toUnsignedString(int,
 410      * int)} method.
 411      *
 412      * @param   i  an integer to be converted to an unsigned string.
 413      * @return  an unsigned string representation of the argument.
 414      * @see     #toUnsignedString(int, int)
 415      * @since 1.8
 416      */
 417     public static String toUnsignedString(int i) {
 418         return Long.toString(toUnsignedLong(i));
 419     }
 420 
 421     /**
 422      * Places characters representing the integer i into the
 423      * character array buf. The characters are placed into
 424      * the buffer backwards starting with the least significant
 425      * digit at the specified index (exclusive), and working
 426      * backwards from there.
 427      *
 428      * Will fail if i == Integer.MIN_VALUE
 429      */
 430     static void getChars(int i, int index, char[] buf) {
 431         int q, r;
 432         int charPos = index;
 433         char sign = 0;
 434 
 435         if (i < 0) {
 436             sign = '-';
 437             i = -i;
 438         }
 439 
 440         // Generate two digits per iteration
 441         while (i >= 65536) {
 442             q = i / 100;
 443         // really: r = i - (q * 100);
 444             r = i - ((q << 6) + (q << 5) + (q << 2));
 445             i = q;
 446             buf [--charPos] = DigitOnes[r];
 447             buf [--charPos] = DigitTens[r];
 448         }
 449 
 450         // Fall thru to fast mode for smaller numbers
 451         // assert(i <= 65536, i);
 452         for (;;) {
 453             q = (i * 52429) >>> (16+3);
 454             r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...
 455             buf [--charPos] = digits [r];
 456             i = q;
 457             if (i == 0) break;
 458         }
 459         if (sign != 0) {
 460             buf [--charPos] = sign;
 461         }
 462     }
 463 
 464     final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
 465                                       99999999, 999999999, Integer.MAX_VALUE };
 466 
 467     // Requires positive x
 468     static int stringSize(int x) {
 469         for (int i=0; ; i++)
 470             if (x <= sizeTable[i])
 471                 return i+1;
 472     }
 473 
 474     /**
 475      * Parses the string argument as a signed integer in the radix
 476      * specified by the second argument. The characters in the string
 477      * must all be digits of the specified radix (as determined by
 478      * whether {@link java.lang.Character#digit(char, int)} returns a
 479      * nonnegative value), except that the first character may be an
 480      * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
 481      * indicate a negative value or an ASCII plus sign {@code '+'}
 482      * ({@code '\u005Cu002B'}) to indicate a positive value. The
 483      * resulting integer value is returned.
 484      *
 485      * <p>An exception of type {@code NumberFormatException} is
 486      * thrown if any of the following situations occurs:
 487      * <ul>
 488      * <li>The first argument is {@code null} or is a string of
 489      * length zero.
 490      *
 491      * <li>The radix is either smaller than
 492      * {@link java.lang.Character#MIN_RADIX} or
 493      * larger than {@link java.lang.Character#MAX_RADIX}.
 494      *
 495      * <li>Any character of the string is not a digit of the specified
 496      * radix, except that the first character may be a minus sign
 497      * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
 498      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 499      * string is longer than length 1.
 500      *
 501      * <li>The value represented by the string is not a value of type
 502      * {@code int}.
 503      * </ul>
 504      *
 505      * <p>Examples:
 506      * <blockquote><pre>
 507      * parseInt("0", 10) returns 0
 508      * parseInt("473", 10) returns 473
 509      * parseInt("+42", 10) returns 42
 510      * parseInt("-0", 10) returns 0
 511      * parseInt("-FF", 16) returns -255
 512      * parseInt("1100110", 2) returns 102
 513      * parseInt("2147483647", 10) returns 2147483647
 514      * parseInt("-2147483648", 10) returns -2147483648
 515      * parseInt("2147483648", 10) throws a NumberFormatException
 516      * parseInt("99", 8) throws a NumberFormatException
 517      * parseInt("Kona", 10) throws a NumberFormatException
 518      * parseInt("Kona", 27) returns 411787
 519      * </pre></blockquote>
 520      *
 521      * @param      s   the {@code String} containing the integer
 522      *                  representation to be parsed
 523      * @param      radix   the radix to be used while parsing {@code s}.
 524      * @return     the integer represented by the string argument in the
 525      *             specified radix.
 526      * @exception  NumberFormatException if the {@code String}
 527      *             does not contain a parsable {@code int}.
 528      */
 529     public static int parseInt(String s, int radix)
 530                 throws NumberFormatException {
 531         return parseInt(s, radix, 0);
 532     }
 533 
 534     /**
 535      * Extend upon Integer.parseInt(String, int) by providing a start offset to enable parsing
 536      * substrings without creating intermediary objects
 537      * @see java.lang.Integer#parseInt(String, int)
 538      *
 539      * @param start the start position in s to parse from, inclusive
 540      */
 541     static int parseInt(CharSequence s, int radix, int start)
 542             throws NumberFormatException {
 543         if (s == null) {
 544             throw new NumberFormatException("null");
 545         }
 546         return parseInt(s, radix, start, s.length());
 547     }
 548 
 549     /**
 550      * Extend upon Integer.parseInt(String, int) by providing a start and end offset to enable parsing
 551      * substrings without creating intermediary objects
 552      * @see java.lang.Integer#parseInt(String, int)
 553      * @param start the start position in s to parse from, inclusive
 554      * @param end the end position in s to parse to, exclusive
 555      */
 556     static int parseInt(CharSequence s, int radix, int start, int end)
 557             throws NumberFormatException {
 558         /*
 559          * WARNING: This method may be invoked early during VM initialization
 560          * before IntegerCache is initialized. Care must be taken to not use
 561          * the valueOf method.
 562          */
 563         if (s == null) {
 564             throw new NumberFormatException("null");
 565         }
 566 
 567         if (radix < Character.MIN_RADIX) {
 568             throw new NumberFormatException("radix " + radix +
 569                                             " less than Character.MIN_RADIX");
 570         }
 571 
 572         if (radix > Character.MAX_RADIX) {
 573             throw new NumberFormatException("radix " + radix +
 574                                             " greater than Character.MAX_RADIX");
 575         }
 576 
 577         if (start < 0 || start > end) {
 578             throw new NumberFormatException("start position out of bounds");
 579         }
 580 
 581         if (start == end) {
 582             throw NumberFormatException.forInputString("");
 583         }
 584 
 585         if (end > s.length()) {
 586             throw new NumberFormatException("end position out of bounds");
 587         }
 588 
 589         int result = 0;
 590         boolean negative = false;
 591         int i = start;
 592         int limit = -Integer.MAX_VALUE;
 593         int multmin;
 594         int digit;
 595 
 596         char firstChar = s.charAt(start);
 597         if (firstChar < '0') { // Possible leading "+" or "-"
 598             if (firstChar == '-') {
 599                 negative = true;
 600                 limit = Integer.MIN_VALUE;
 601             } else if (firstChar != '+') {
 602                 throw NumberFormatException.forInputString(
 603                         s.subSequence(start, end).toString());
 604             }
 605 
 606             if (end == start + 1) { // Cannot have lone "+" or "-"
 607                 throw NumberFormatException.forInputString(
 608                         s.subSequence(start, end).toString());
 609             }
 610             i++;
 611         }
 612         multmin = limit / radix;
 613         while (i < end) {
 614             // Accumulating negatively avoids surprises near MAX_VALUE
 615             digit = Character.digit(s.charAt(i++), radix);
 616             if (digit < 0) {
 617                 throw NumberFormatException.forInputString(
 618                         s.subSequence(start, end).toString());
 619             }
 620             if (result < multmin) {
 621                 throw NumberFormatException.forInputString(
 622                         s.subSequence(start, end).toString());
 623             }
 624             result *= radix;
 625             if (result < limit + digit) {
 626                 throw NumberFormatException.forInputString(
 627                         s.subSequence(start, end).toString());
 628             }
 629             result -= digit;
 630         }
 631         return negative ? result : -result;
 632     }
 633 
 634     /**
 635      * Parses the string argument as a signed decimal integer. The
 636      * characters in the string must all be decimal digits, except
 637      * that the first character may be an ASCII minus sign {@code '-'}
 638      * ({@code '\u005Cu002D'}) to indicate a negative value or an
 639      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
 640      * indicate a positive value. The resulting integer value is
 641      * returned, exactly as if the argument and the radix 10 were
 642      * given as arguments to the {@link #parseInt(java.lang.String,
 643      * int)} method.
 644      *
 645      * @param s    a {@code String} containing the {@code int}
 646      *             representation to be parsed
 647      * @return     the integer value represented by the argument in decimal.
 648      * @exception  NumberFormatException  if the string does not contain a
 649      *               parsable integer.
 650      */
 651     public static int parseInt(String s) throws NumberFormatException {
 652         return parseInt(s,10);
 653     }
 654 
 655     /**
 656      * Parses the string argument as an unsigned integer in the radix
 657      * specified by the second argument.  An unsigned integer maps the
 658      * values usually associated with negative numbers to positive
 659      * numbers larger than {@code MAX_VALUE}.
 660      *
 661      * The characters in the string must all be digits of the
 662      * specified radix (as determined by whether {@link
 663      * java.lang.Character#digit(char, int)} returns a nonnegative
 664      * value), except that the first character may be an ASCII plus
 665      * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
 666      * integer value is returned.
 667      *
 668      * <p>An exception of type {@code NumberFormatException} is
 669      * thrown if any of the following situations occurs:
 670      * <ul>
 671      * <li>The first argument is {@code null} or is a string of
 672      * length zero.
 673      *
 674      * <li>The radix is either smaller than
 675      * {@link java.lang.Character#MIN_RADIX} or
 676      * larger than {@link java.lang.Character#MAX_RADIX}.
 677      *
 678      * <li>Any character of the string is not a digit of the specified
 679      * radix, except that the first character may be a plus sign
 680      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 681      * string is longer than length 1.
 682      *
 683      * <li>The value represented by the string is larger than the
 684      * largest unsigned {@code int}, 2<sup>32</sup>-1.
 685      *
 686      * </ul>
 687      *
 688      *
 689      * @param      s   the {@code String} containing the unsigned integer
 690      *                  representation to be parsed
 691      * @param      radix   the radix to be used while parsing {@code s}.
 692      * @return     the integer represented by the string argument in the
 693      *             specified radix.
 694      * @throws     NumberFormatException if the {@code String}
 695      *             does not contain a parsable {@code int}.
 696      * @since 1.8
 697      */
 698     public static int parseUnsignedInt(String s, int radix)
 699                 throws NumberFormatException {
 700         return parseUnsignedInt(s, radix, 0);
 701     }
 702 
 703     /**
 704      * Extend upon parseUnsignedInt(String, int) by providing a start offset
 705      * to enable parsing substrings without creating intermediary objects
 706      * @see java.lang.Integer#parseUnsignedInt(String, int)
 707      * @param start the start position in s to parse from, inclusive
 708      */
 709     static int parseUnsignedInt(CharSequence s, int radix, int start)
 710             throws NumberFormatException {
 711         if (s == null) {
 712             throw new NumberFormatException("null");
 713         }
 714         return parseUnsignedInt(s, radix, start, s.length());
 715     }
 716 
 717     /**
 718      * Extend upon parseUnsignedInt(String, int) by providing a start and end
 719      * offset to enable parsing substrings without creating intermediary objects
 720      * @see java.lang.Integer#parseUnsignedInt(String, int)
 721      * @param start the start position in s to parse from, inclusive
 722      * @param end the end position in s to parse to, exclusive
 723      */
 724     static int parseUnsignedInt(CharSequence s, int radix, int start, int end)
 725             throws NumberFormatException {
 726         if (s == null) {
 727             throw new NumberFormatException("null");
 728         }
 729         int len = end - start;
 730         if (len > 0) {
 731             char firstChar = s.charAt(start);
 732             if (firstChar == '-') {
 733                 throw new
 734                     NumberFormatException(String.format("Illegal leading minus sign " +
 735                                                        "on unsigned string %s.", s));
 736             } else {
 737                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 738                     (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
 739                     return parseInt(s, radix, start, end);
 740                 } else {
 741                     long ell = Long.parseLong(s, radix, start, end);
 742                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 743                         return (int) ell;
 744                     } else {
 745                         throw new
 746                             NumberFormatException(String.format("String value %s exceeds " +
 747                                                                 "range of unsigned int.", s));
 748                     }
 749                 }
 750             }
 751         } else {
 752             throw NumberFormatException.forInputString(s.toString());
 753         }
 754     }
 755 
 756     /**
 757      * Parses the string argument as an unsigned decimal integer. The
 758      * characters in the string must all be decimal digits, except
 759      * that the first character may be an an ASCII plus sign {@code
 760      * '+'} ({@code '\u005Cu002B'}). The resulting integer value
 761      * is returned, exactly as if the argument and the radix 10 were
 762      * given as arguments to the {@link
 763      * #parseUnsignedInt(java.lang.String, int)} method.
 764      *
 765      * @param s   a {@code String} containing the unsigned {@code int}
 766      *            representation to be parsed
 767      * @return    the unsigned integer value represented by the argument in decimal.
 768      * @throws    NumberFormatException  if the string does not contain a
 769      *            parsable unsigned integer.
 770      * @since 1.8
 771      */
 772     public static int parseUnsignedInt(String s) throws NumberFormatException {
 773         return parseUnsignedInt(s, 10);
 774     }
 775 
 776     /**
 777      * Returns an {@code Integer} object holding the value
 778      * extracted from the specified {@code String} when parsed
 779      * with the radix given by the second argument. The first argument
 780      * is interpreted as representing a signed integer in the radix
 781      * specified by the second argument, exactly as if the arguments
 782      * were given to the {@link #parseInt(java.lang.String, int)}
 783      * method. The result is an {@code Integer} object that
 784      * represents the integer value specified by the string.
 785      *
 786      * <p>In other words, this method returns an {@code Integer}
 787      * object equal to the value of:
 788      *
 789      * <blockquote>
 790      *  {@code new Integer(Integer.parseInt(s, radix))}
 791      * </blockquote>
 792      *
 793      * @param      s   the string to be parsed.
 794      * @param      radix the radix to be used in interpreting {@code s}
 795      * @return     an {@code Integer} object holding the value
 796      *             represented by the string argument in the specified
 797      *             radix.
 798      * @exception NumberFormatException if the {@code String}
 799      *            does not contain a parsable {@code int}.
 800      */
 801     public static Integer valueOf(String s, int radix) throws NumberFormatException {
 802         return Integer.valueOf(parseInt(s,radix));
 803     }
 804 
 805     /**
 806      * Returns an {@code Integer} object holding the
 807      * value of the specified {@code String}. The argument is
 808      * interpreted as representing a signed decimal integer, exactly
 809      * as if the argument were given to the {@link
 810      * #parseInt(java.lang.String)} method. The result is an
 811      * {@code Integer} object that represents the integer value
 812      * specified by the string.
 813      *
 814      * <p>In other words, this method returns an {@code Integer}
 815      * object equal to the value of:
 816      *
 817      * <blockquote>
 818      *  {@code new Integer(Integer.parseInt(s))}
 819      * </blockquote>
 820      *
 821      * @param      s   the string to be parsed.
 822      * @return     an {@code Integer} object holding the value
 823      *             represented by the string argument.
 824      * @exception  NumberFormatException  if the string cannot be parsed
 825      *             as an integer.
 826      */
 827     public static Integer valueOf(String s) throws NumberFormatException {
 828         return Integer.valueOf(parseInt(s, 10));
 829     }
 830 
 831     /**
 832      * Cache to support the object identity semantics of autoboxing for values between
 833      * -128 and 127 (inclusive) as required by JLS.
 834      *
 835      * The cache is initialized on first usage.  The size of the cache
 836      * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
 837      * During VM initialization, java.lang.Integer.IntegerCache.high property
 838      * may be set and saved in the private system properties in the
 839      * sun.misc.VM class.
 840      */
 841 
 842     private static class IntegerCache {
 843         static final int low = -128;
 844         static final int high;
 845         static final Integer cache[];
 846 
 847         static {
 848             // high value may be configured by property
 849             int h = 127;
 850             String integerCacheHighPropValue =
 851                 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
 852             if (integerCacheHighPropValue != null) {
 853                 try {
 854                     int i = parseInt(integerCacheHighPropValue);
 855                     i = Math.max(i, 127);
 856                     // Maximum array size is Integer.MAX_VALUE
 857                     h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
 858                 } catch( NumberFormatException nfe) {
 859                     // If the property cannot be parsed into an int, ignore it.
 860                 }
 861             }
 862             high = h;
 863 
 864             cache = new Integer[(high - low) + 1];
 865             int j = low;
 866             for(int k = 0; k < cache.length; k++)
 867                 cache[k] = new Integer(j++);
 868 
 869             // range [-128, 127] must be interned (JLS7 5.1.7)
 870             assert IntegerCache.high >= 127;
 871         }
 872 
 873         private IntegerCache() {}
 874     }
 875 
 876     /**
 877      * Returns an {@code Integer} instance representing the specified
 878      * {@code int} value.  If a new {@code Integer} instance is not
 879      * required, this method should generally be used in preference to
 880      * the constructor {@link #Integer(int)}, as this method is likely
 881      * to yield significantly better space and time performance by
 882      * caching frequently requested values.
 883      *
 884      * This method will always cache values in the range -128 to 127,
 885      * inclusive, and may cache other values outside of this range.
 886      *
 887      * @param  i an {@code int} value.
 888      * @return an {@code Integer} instance representing {@code i}.
 889      * @since  1.5
 890      */
 891     public static Integer valueOf(int i) {
 892         if (i >= IntegerCache.low && i <= IntegerCache.high)
 893             return IntegerCache.cache[i + (-IntegerCache.low)];
 894         return new Integer(i);
 895     }
 896 
 897     /**
 898      * The value of the {@code Integer}.
 899      *
 900      * @serial
 901      */
 902     private final int value;
 903 
 904     /**
 905      * Constructs a newly allocated {@code Integer} object that
 906      * represents the specified {@code int} value.
 907      *
 908      * @param   value   the value to be represented by the
 909      *                  {@code Integer} object.
 910      */
 911     public Integer(int value) {
 912         this.value = value;
 913     }
 914 
 915     /**
 916      * Constructs a newly allocated {@code Integer} object that
 917      * represents the {@code int} value indicated by the
 918      * {@code String} parameter. The string is converted to an
 919      * {@code int} value in exactly the manner used by the
 920      * {@code parseInt} method for radix 10.
 921      *
 922      * @param      s   the {@code String} to be converted to an
 923      *                 {@code Integer}.
 924      * @exception  NumberFormatException  if the {@code String} does not
 925      *               contain a parsable integer.
 926      * @see        java.lang.Integer#parseInt(java.lang.String, int)
 927      */
 928     public Integer(String s) throws NumberFormatException {
 929         this.value = parseInt(s, 10);
 930     }
 931 
 932     /**
 933      * Returns the value of this {@code Integer} as a {@code byte}
 934      * after a narrowing primitive conversion.
 935      * @jls 5.1.3 Narrowing Primitive Conversions
 936      */
 937     public byte byteValue() {
 938         return (byte)value;
 939     }
 940 
 941     /**
 942      * Returns the value of this {@code Integer} as a {@code short}
 943      * after a narrowing primitive conversion.
 944      * @jls 5.1.3 Narrowing Primitive Conversions
 945      */
 946     public short shortValue() {
 947         return (short)value;
 948     }
 949 
 950     /**
 951      * Returns the value of this {@code Integer} as an
 952      * {@code int}.
 953      */
 954     public int intValue() {
 955         return value;
 956     }
 957 
 958     /**
 959      * Returns the value of this {@code Integer} as a {@code long}
 960      * after a widening primitive conversion.
 961      * @jls 5.1.2 Widening Primitive Conversions
 962      * @see Integer#toUnsignedLong(int)
 963      */
 964     public long longValue() {
 965         return (long)value;
 966     }
 967 
 968     /**
 969      * Returns the value of this {@code Integer} as a {@code float}
 970      * after a widening primitive conversion.
 971      * @jls 5.1.2 Widening Primitive Conversions
 972      */
 973     public float floatValue() {
 974         return (float)value;
 975     }
 976 
 977     /**
 978      * Returns the value of this {@code Integer} as a {@code double}
 979      * after a widening primitive conversion.
 980      * @jls 5.1.2 Widening Primitive Conversions
 981      */
 982     public double doubleValue() {
 983         return (double)value;
 984     }
 985 
 986     /**
 987      * Returns a {@code String} object representing this
 988      * {@code Integer}'s value. The value is converted to signed
 989      * decimal representation and returned as a string, exactly as if
 990      * the integer value were given as an argument to the {@link
 991      * java.lang.Integer#toString(int)} method.
 992      *
 993      * @return  a string representation of the value of this object in
 994      *          base&nbsp;10.
 995      */
 996     public String toString() {
 997         return toString(value);
 998     }
 999 
1000     /**
1001      * Returns a hash code for this {@code Integer}.
1002      *
1003      * @return  a hash code value for this object, equal to the
1004      *          primitive {@code int} value represented by this
1005      *          {@code Integer} object.
1006      */
1007     @Override
1008     public int hashCode() {
1009         return Integer.hashCode(value);
1010     }
1011 
1012     /**
1013      * Returns a hash code for a {@code int} value; compatible with
1014      * {@code Integer.hashCode()}.
1015      *
1016      * @param value the value to hash
1017      * @since 1.8
1018      *
1019      * @return a hash code value for a {@code int} value.
1020      */
1021     public static int hashCode(int value) {
1022         return value;
1023     }
1024 
1025     /**
1026      * Compares this object to the specified object.  The result is
1027      * {@code true} if and only if the argument is not
1028      * {@code null} and is an {@code Integer} object that
1029      * contains the same {@code int} value as this object.
1030      *
1031      * @param   obj   the object to compare with.
1032      * @return  {@code true} if the objects are the same;
1033      *          {@code false} otherwise.
1034      */
1035     public boolean equals(Object obj) {
1036         if (obj instanceof Integer) {
1037             return value == ((Integer)obj).intValue();
1038         }
1039         return false;
1040     }
1041 
1042     /**
1043      * Determines the integer value of the system property with the
1044      * specified name.
1045      *
1046      * <p>The first argument is treated as the name of a system
1047      * property.  System properties are accessible through the {@link
1048      * java.lang.System#getProperty(java.lang.String)} method. The
1049      * string value of this property is then interpreted as an integer
1050      * value using the grammar supported by {@link Integer#decode decode} and
1051      * an {@code Integer} object representing this value is returned.
1052      *
1053      * <p>If there is no property with the specified name, if the
1054      * specified name is empty or {@code null}, or if the property
1055      * does not have the correct numeric format, then {@code null} is
1056      * returned.
1057      *
1058      * <p>In other words, this method returns an {@code Integer}
1059      * object equal to the value of:
1060      *
1061      * <blockquote>
1062      *  {@code getInteger(nm, null)}
1063      * </blockquote>
1064      *
1065      * @param   nm   property name.
1066      * @return  the {@code Integer} value of the property.
1067      * @throws  SecurityException for the same reasons as
1068      *          {@link System#getProperty(String) System.getProperty}
1069      * @see     java.lang.System#getProperty(java.lang.String)
1070      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1071      */
1072     public static Integer getInteger(String nm) {
1073         return getInteger(nm, null);
1074     }
1075 
1076     /**
1077      * Determines the integer value of the system property with the
1078      * specified name.
1079      *
1080      * <p>The first argument is treated as the name of a system
1081      * property.  System properties are accessible through the {@link
1082      * java.lang.System#getProperty(java.lang.String)} method. The
1083      * string value of this property is then interpreted as an integer
1084      * value using the grammar supported by {@link Integer#decode decode} and
1085      * an {@code Integer} object representing this value is returned.
1086      *
1087      * <p>The second argument is the default value. An {@code Integer} object
1088      * that represents the value of the second argument is returned if there
1089      * is no property of the specified name, if the property does not have
1090      * the correct numeric format, or if the specified name is empty or
1091      * {@code null}.
1092      *
1093      * <p>In other words, this method returns an {@code Integer} object
1094      * equal to the value of:
1095      *
1096      * <blockquote>
1097      *  {@code getInteger(nm, new Integer(val))}
1098      * </blockquote>
1099      *
1100      * but in practice it may be implemented in a manner such as:
1101      *
1102      * <blockquote><pre>
1103      * Integer result = getInteger(nm, null);
1104      * return (result == null) ? new Integer(val) : result;
1105      * </pre></blockquote>
1106      *
1107      * to avoid the unnecessary allocation of an {@code Integer}
1108      * object when the default value is not needed.
1109      *
1110      * @param   nm   property name.
1111      * @param   val   default value.
1112      * @return  the {@code Integer} value of the property.
1113      * @throws  SecurityException for the same reasons as
1114      *          {@link System#getProperty(String) System.getProperty}
1115      * @see     java.lang.System#getProperty(java.lang.String)
1116      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1117      */
1118     public static Integer getInteger(String nm, int val) {
1119         Integer result = getInteger(nm, null);
1120         return (result == null) ? Integer.valueOf(val) : result;
1121     }
1122 
1123     /**
1124      * Returns the integer value of the system property with the
1125      * specified name.  The first argument is treated as the name of a
1126      * system property.  System properties are accessible through the
1127      * {@link java.lang.System#getProperty(java.lang.String)} method.
1128      * The string value of this property is then interpreted as an
1129      * integer value, as per the {@link Integer#decode decode} method,
1130      * and an {@code Integer} object representing this value is
1131      * returned; in summary:
1132      *
1133      * <ul><li>If the property value begins with the two ASCII characters
1134      *         {@code 0x} or the ASCII character {@code #}, not
1135      *      followed by a minus sign, then the rest of it is parsed as a
1136      *      hexadecimal integer exactly as by the method
1137      *      {@link #valueOf(java.lang.String, int)} with radix 16.
1138      * <li>If the property value begins with the ASCII character
1139      *     {@code 0} followed by another character, it is parsed as an
1140      *     octal integer exactly as by the method
1141      *     {@link #valueOf(java.lang.String, int)} with radix 8.
1142      * <li>Otherwise, the property value is parsed as a decimal integer
1143      * exactly as by the method {@link #valueOf(java.lang.String, int)}
1144      * with radix 10.
1145      * </ul>
1146      *
1147      * <p>The second argument is the default value. The default value is
1148      * returned if there is no property of the specified name, if the
1149      * property does not have the correct numeric format, or if the
1150      * specified name is empty or {@code null}.
1151      *
1152      * @param   nm   property name.
1153      * @param   val   default value.
1154      * @return  the {@code Integer} value of the property.
1155      * @throws  SecurityException for the same reasons as
1156      *          {@link System#getProperty(String) System.getProperty}
1157      * @see     System#getProperty(java.lang.String)
1158      * @see     System#getProperty(java.lang.String, java.lang.String)
1159      */
1160     public static Integer getInteger(String nm, Integer val) {
1161         String v = null;
1162         try {
1163             v = System.getProperty(nm);
1164         } catch (IllegalArgumentException | NullPointerException e) {
1165         }
1166         if (v != null) {
1167             try {
1168                 return Integer.decode(v);
1169             } catch (NumberFormatException e) {
1170             }
1171         }
1172         return val;
1173     }
1174 
1175     /**
1176      * Decodes a {@code String} into an {@code Integer}.
1177      * Accepts decimal, hexadecimal, and octal numbers given
1178      * by the following grammar:
1179      *
1180      * <blockquote>
1181      * <dl>
1182      * <dt><i>DecodableString:</i>
1183      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1184      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1185      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1186      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1187      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1188      *
1189      * <dt><i>Sign:</i>
1190      * <dd>{@code -}
1191      * <dd>{@code +}
1192      * </dl>
1193      * </blockquote>
1194      *
1195      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1196      * are as defined in section 3.10.1 of
1197      * <cite>The Java&trade; Language Specification</cite>,
1198      * except that underscores are not accepted between digits.
1199      *
1200      * <p>The sequence of characters following an optional
1201      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1202      * "{@code #}", or leading zero) is parsed as by the {@code
1203      * Integer.parseInt} method with the indicated radix (10, 16, or
1204      * 8).  This sequence of characters must represent a positive
1205      * value or a {@link NumberFormatException} will be thrown.  The
1206      * result is negated if first character of the specified {@code
1207      * String} is the minus sign.  No whitespace characters are
1208      * permitted in the {@code String}.
1209      *
1210      * @param     nm the {@code String} to decode.
1211      * @return    an {@code Integer} object holding the {@code int}
1212      *             value represented by {@code nm}
1213      * @exception NumberFormatException  if the {@code String} does not
1214      *            contain a parsable integer.
1215      * @see java.lang.Integer#parseInt(java.lang.String, int)
1216      */
1217     public static Integer decode(String nm) throws NumberFormatException {
1218         int radix = 10;
1219         int index = 0;
1220         boolean negative = false;
1221         Integer result;
1222 
1223         if (nm.length() == 0)
1224             throw new NumberFormatException("Zero length string");
1225         char firstChar = nm.charAt(0);
1226         // Handle sign, if present
1227         if (firstChar == '-') {
1228             negative = true;
1229             index++;
1230         } else if (firstChar == '+')
1231             index++;
1232 
1233         // Handle radix specifier, if present
1234         if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1235             index += 2;
1236             radix = 16;
1237         }
1238         else if (nm.startsWith("#", index)) {
1239             index ++;
1240             radix = 16;
1241         }
1242         else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1243             index ++;
1244             radix = 8;
1245         }
1246 
1247         if (nm.startsWith("-", index) || nm.startsWith("+", index))
1248             throw new NumberFormatException("Sign character in wrong position");
1249 
1250         try {
1251             result = Integer.valueOf(nm.substring(index), radix);
1252             result = negative ? Integer.valueOf(-result.intValue()) : result;
1253         } catch (NumberFormatException e) {
1254             // If number is Integer.MIN_VALUE, we'll end up here. The next line
1255             // handles this case, and causes any genuine format error to be
1256             // rethrown.
1257             String constant = negative ? ("-" + nm.substring(index))
1258                                        : nm.substring(index);
1259             result = Integer.valueOf(constant, radix);
1260         }
1261         return result;
1262     }
1263 
1264     /**
1265      * Compares two {@code Integer} objects numerically.
1266      *
1267      * @param   anotherInteger   the {@code Integer} to be compared.
1268      * @return  the value {@code 0} if this {@code Integer} is
1269      *          equal to the argument {@code Integer}; a value less than
1270      *          {@code 0} if this {@code Integer} is numerically less
1271      *          than the argument {@code Integer}; and a value greater
1272      *          than {@code 0} if this {@code Integer} is numerically
1273      *           greater than the argument {@code Integer} (signed
1274      *           comparison).
1275      * @since   1.2
1276      */
1277     public int compareTo(Integer anotherInteger) {
1278         return compare(this.value, anotherInteger.value);
1279     }
1280 
1281     /**
1282      * Compares two {@code int} values numerically.
1283      * The value returned is identical to what would be returned by:
1284      * <pre>
1285      *    Integer.valueOf(x).compareTo(Integer.valueOf(y))
1286      * </pre>
1287      *
1288      * @param  x the first {@code int} to compare
1289      * @param  y the second {@code int} to compare
1290      * @return the value {@code 0} if {@code x == y};
1291      *         a value less than {@code 0} if {@code x < y}; and
1292      *         a value greater than {@code 0} if {@code x > y}
1293      * @since 1.7
1294      */
1295     public static int compare(int x, int y) {
1296         return (x < y) ? -1 : ((x == y) ? 0 : 1);
1297     }
1298 
1299     /**
1300      * Compares two {@code int} values numerically treating the values
1301      * as unsigned.
1302      *
1303      * @param  x the first {@code int} to compare
1304      * @param  y the second {@code int} to compare
1305      * @return the value {@code 0} if {@code x == y}; a value less
1306      *         than {@code 0} if {@code x < y} as unsigned values; and
1307      *         a value greater than {@code 0} if {@code x > y} as
1308      *         unsigned values
1309      * @since 1.8
1310      */
1311     public static int compareUnsigned(int x, int y) {
1312         return compare(x + MIN_VALUE, y + MIN_VALUE);
1313     }
1314 
1315     /**
1316      * Converts the argument to a {@code long} by an unsigned
1317      * conversion.  In an unsigned conversion to a {@code long}, the
1318      * high-order 32 bits of the {@code long} are zero and the
1319      * low-order 32 bits are equal to the bits of the integer
1320      * argument.
1321      *
1322      * Consequently, zero and positive {@code int} values are mapped
1323      * to a numerically equal {@code long} value and negative {@code
1324      * int} values are mapped to a {@code long} value equal to the
1325      * input plus 2<sup>32</sup>.
1326      *
1327      * @param  x the value to convert to an unsigned {@code long}
1328      * @return the argument converted to {@code long} by an unsigned
1329      *         conversion
1330      * @since 1.8
1331      */
1332     public static long toUnsignedLong(int x) {
1333         return ((long) x) & 0xffffffffL;
1334     }
1335 
1336     /**
1337      * Returns the unsigned quotient of dividing the first argument by
1338      * the second where each argument and the result is interpreted as
1339      * an unsigned value.
1340      *
1341      * <p>Note that in two's complement arithmetic, the three other
1342      * basic arithmetic operations of add, subtract, and multiply are
1343      * bit-wise identical if the two operands are regarded as both
1344      * being signed or both being unsigned.  Therefore separate {@code
1345      * addUnsigned}, etc. methods are not provided.
1346      *
1347      * @param dividend the value to be divided
1348      * @param divisor the value doing the dividing
1349      * @return the unsigned quotient of the first argument divided by
1350      * the second argument
1351      * @see #remainderUnsigned
1352      * @since 1.8
1353      */
1354     public static int divideUnsigned(int dividend, int divisor) {
1355         // In lieu of tricky code, for now just use long arithmetic.
1356         return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1357     }
1358 
1359     /**
1360      * Returns the unsigned remainder from dividing the first argument
1361      * by the second where each argument and the result is interpreted
1362      * as an unsigned value.
1363      *
1364      * @param dividend the value to be divided
1365      * @param divisor the value doing the dividing
1366      * @return the unsigned remainder of the first argument divided by
1367      * the second argument
1368      * @see #divideUnsigned
1369      * @since 1.8
1370      */
1371     public static int remainderUnsigned(int dividend, int divisor) {
1372         // In lieu of tricky code, for now just use long arithmetic.
1373         return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1374     }
1375 
1376 
1377     // Bit twiddling
1378 
1379     /**
1380      * The number of bits used to represent an {@code int} value in two's
1381      * complement binary form.
1382      *
1383      * @since 1.5
1384      */
1385     @Native public static final int SIZE = 32;
1386 
1387     /**
1388      * The number of bytes used to represent a {@code int} value in two's
1389      * complement binary form.
1390      *
1391      * @since 1.8
1392      */
1393     public static final int BYTES = SIZE / Byte.SIZE;
1394 
1395     /**
1396      * Returns an {@code int} value with at most a single one-bit, in the
1397      * position of the highest-order ("leftmost") one-bit in the specified
1398      * {@code int} value.  Returns zero if the specified value has no
1399      * one-bits in its two's complement binary representation, that is, if it
1400      * is equal to zero.
1401      *
1402      * @param i the value whose highest one bit is to be computed
1403      * @return an {@code int} value with a single one-bit, in the position
1404      *     of the highest-order one-bit in the specified value, or zero if
1405      *     the specified value is itself equal to zero.
1406      * @since 1.5
1407      */
1408     public static int highestOneBit(int i) {
1409         // HD, Figure 3-1
1410         i |= (i >>  1);
1411         i |= (i >>  2);
1412         i |= (i >>  4);
1413         i |= (i >>  8);
1414         i |= (i >> 16);
1415         return i - (i >>> 1);
1416     }
1417 
1418     /**
1419      * Returns an {@code int} value with at most a single one-bit, in the
1420      * position of the lowest-order ("rightmost") one-bit in the specified
1421      * {@code int} value.  Returns zero if the specified value has no
1422      * one-bits in its two's complement binary representation, that is, if it
1423      * is equal to zero.
1424      *
1425      * @param i the value whose lowest one bit is to be computed
1426      * @return an {@code int} value with a single one-bit, in the position
1427      *     of the lowest-order one-bit in the specified value, or zero if
1428      *     the specified value is itself equal to zero.
1429      * @since 1.5
1430      */
1431     public static int lowestOneBit(int i) {
1432         // HD, Section 2-1
1433         return i & -i;
1434     }
1435 
1436     /**
1437      * Returns the number of zero bits preceding the highest-order
1438      * ("leftmost") one-bit in the two's complement binary representation
1439      * of the specified {@code int} value.  Returns 32 if the
1440      * specified value has no one-bits in its two's complement representation,
1441      * in other words if it is equal to zero.
1442      *
1443      * <p>Note that this method is closely related to the logarithm base 2.
1444      * For all positive {@code int} values x:
1445      * <ul>
1446      * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1447      * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1448      * </ul>
1449      *
1450      * @param i the value whose number of leading zeros is to be computed
1451      * @return the number of zero bits preceding the highest-order
1452      *     ("leftmost") one-bit in the two's complement binary representation
1453      *     of the specified {@code int} value, or 32 if the value
1454      *     is equal to zero.
1455      * @since 1.5
1456      */
1457     public static int numberOfLeadingZeros(int i) {
1458         // HD, Figure 5-6
1459         if (i == 0)
1460             return 32;
1461         int n = 1;
1462         if (i >>> 16 == 0) { n += 16; i <<= 16; }
1463         if (i >>> 24 == 0) { n +=  8; i <<=  8; }
1464         if (i >>> 28 == 0) { n +=  4; i <<=  4; }
1465         if (i >>> 30 == 0) { n +=  2; i <<=  2; }
1466         n -= i >>> 31;
1467         return n;
1468     }
1469 
1470     /**
1471      * Returns the number of zero bits following the lowest-order ("rightmost")
1472      * one-bit in the two's complement binary representation of the specified
1473      * {@code int} value.  Returns 32 if the specified value has no
1474      * one-bits in its two's complement representation, in other words if it is
1475      * equal to zero.
1476      *
1477      * @param i the value whose number of trailing zeros is to be computed
1478      * @return the number of zero bits following the lowest-order ("rightmost")
1479      *     one-bit in the two's complement binary representation of the
1480      *     specified {@code int} value, or 32 if the value is equal
1481      *     to zero.
1482      * @since 1.5
1483      */
1484     public static int numberOfTrailingZeros(int i) {
1485         // HD, Figure 5-14
1486         int y;
1487         if (i == 0) return 32;
1488         int n = 31;
1489         y = i <<16; if (y != 0) { n = n -16; i = y; }
1490         y = i << 8; if (y != 0) { n = n - 8; i = y; }
1491         y = i << 4; if (y != 0) { n = n - 4; i = y; }
1492         y = i << 2; if (y != 0) { n = n - 2; i = y; }
1493         return n - ((i << 1) >>> 31);
1494     }
1495 
1496     /**
1497      * Returns the number of one-bits in the two's complement binary
1498      * representation of the specified {@code int} value.  This function is
1499      * sometimes referred to as the <i>population count</i>.
1500      *
1501      * @param i the value whose bits are to be counted
1502      * @return the number of one-bits in the two's complement binary
1503      *     representation of the specified {@code int} value.
1504      * @since 1.5
1505      */
1506     public static int bitCount(int i) {
1507         // HD, Figure 5-2
1508         i = i - ((i >>> 1) & 0x55555555);
1509         i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1510         i = (i + (i >>> 4)) & 0x0f0f0f0f;
1511         i = i + (i >>> 8);
1512         i = i + (i >>> 16);
1513         return i & 0x3f;
1514     }
1515 
1516     /**
1517      * Returns the value obtained by rotating the two's complement binary
1518      * representation of the specified {@code int} value left by the
1519      * specified number of bits.  (Bits shifted out of the left hand, or
1520      * high-order, side reenter on the right, or low-order.)
1521      *
1522      * <p>Note that left rotation with a negative distance is equivalent to
1523      * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1524      * distance)}.  Note also that rotation by any multiple of 32 is a
1525      * no-op, so all but the last five bits of the rotation distance can be
1526      * ignored, even if the distance is negative: {@code rotateLeft(val,
1527      * distance) == rotateLeft(val, distance & 0x1F)}.
1528      *
1529      * @param i the value whose bits are to be rotated left
1530      * @param distance the number of bit positions to rotate left
1531      * @return the value obtained by rotating the two's complement binary
1532      *     representation of the specified {@code int} value left by the
1533      *     specified number of bits.
1534      * @since 1.5
1535      */
1536     public static int rotateLeft(int i, int distance) {
1537         return (i << distance) | (i >>> -distance);
1538     }
1539 
1540     /**
1541      * Returns the value obtained by rotating the two's complement binary
1542      * representation of the specified {@code int} value right by the
1543      * specified number of bits.  (Bits shifted out of the right hand, or
1544      * low-order, side reenter on the left, or high-order.)
1545      *
1546      * <p>Note that right rotation with a negative distance is equivalent to
1547      * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1548      * distance)}.  Note also that rotation by any multiple of 32 is a
1549      * no-op, so all but the last five bits of the rotation distance can be
1550      * ignored, even if the distance is negative: {@code rotateRight(val,
1551      * distance) == rotateRight(val, distance & 0x1F)}.
1552      *
1553      * @param i the value whose bits are to be rotated right
1554      * @param distance the number of bit positions to rotate right
1555      * @return the value obtained by rotating the two's complement binary
1556      *     representation of the specified {@code int} value right by the
1557      *     specified number of bits.
1558      * @since 1.5
1559      */
1560     public static int rotateRight(int i, int distance) {
1561         return (i >>> distance) | (i << -distance);
1562     }
1563 
1564     /**
1565      * Returns the value obtained by reversing the order of the bits in the
1566      * two's complement binary representation of the specified {@code int}
1567      * value.
1568      *
1569      * @param i the value to be reversed
1570      * @return the value obtained by reversing order of the bits in the
1571      *     specified {@code int} value.
1572      * @since 1.5
1573      */
1574     public static int reverse(int i) {
1575         // HD, Figure 7-1
1576         i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1577         i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1578         i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1579         i = (i << 24) | ((i & 0xff00) << 8) |
1580             ((i >>> 8) & 0xff00) | (i >>> 24);
1581         return i;
1582     }
1583 
1584     /**
1585      * Returns the signum function of the specified {@code int} value.  (The
1586      * return value is -1 if the specified value is negative; 0 if the
1587      * specified value is zero; and 1 if the specified value is positive.)
1588      *
1589      * @param i the value whose signum is to be computed
1590      * @return the signum function of the specified {@code int} value.
1591      * @since 1.5
1592      */
1593     public static int signum(int i) {
1594         // HD, Section 2-7
1595         return (i >> 31) | (-i >>> 31);
1596     }
1597 
1598     /**
1599      * Returns the value obtained by reversing the order of the bytes in the
1600      * two's complement representation of the specified {@code int} value.
1601      *
1602      * @param i the value whose bytes are to be reversed
1603      * @return the value obtained by reversing the bytes in the specified
1604      *     {@code int} value.
1605      * @since 1.5
1606      */
1607     public static int reverseBytes(int i) {
1608         return ((i >>> 24)           ) |
1609                ((i >>   8) &   0xFF00) |
1610                ((i <<   8) & 0xFF0000) |
1611                ((i << 24));
1612     }
1613 
1614     /**
1615      * Adds two integers together as per the + operator.
1616      *
1617      * @param a the first operand
1618      * @param b the second operand
1619      * @return the sum of {@code a} and {@code b}
1620      * @see java.util.function.BinaryOperator
1621      * @since 1.8
1622      */
1623     public static int sum(int a, int b) {
1624         return a + b;
1625     }
1626 
1627     /**
1628      * Returns the greater of two {@code int} values
1629      * as if by calling {@link Math#max(int, int) Math.max}.
1630      *
1631      * @param a the first operand
1632      * @param b the second operand
1633      * @return the greater of {@code a} and {@code b}
1634      * @see java.util.function.BinaryOperator
1635      * @since 1.8
1636      */
1637     public static int max(int a, int b) {
1638         return Math.max(a, b);
1639     }
1640 
1641     /**
1642      * Returns the smaller of two {@code int} values
1643      * as if by calling {@link Math#min(int, int) Math.min}.
1644      *
1645      * @param a the first operand
1646      * @param b the second operand
1647      * @return the smaller of {@code a} and {@code b}
1648      * @see java.util.function.BinaryOperator
1649      * @since 1.8
1650      */
1651     public static int min(int a, int b) {
1652         return Math.min(a, b);
1653     }
1654 
1655     /** use serialVersionUID from JDK 1.0.2 for interoperability */
1656     @Native private static final long serialVersionUID = 1360826667806852920L;
1657 }