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 import java.util.Objects;
  30 
  31 /**
  32  * The {@code Integer} class wraps a value of the primitive type
  33  * {@code int} in an object. An object of type {@code Integer}
  34  * contains a single field whose type is {@code int}.
  35  *
  36  * <p>In addition, this class provides several methods for converting
  37  * an {@code int} to a {@code String} and a {@code String} to an
  38  * {@code int}, as well as other constants and methods useful when
  39  * dealing with an {@code int}.
  40  *
  41  * <p>Implementation note: The implementations of the "bit twiddling"
  42  * methods (such as {@link #highestOneBit(int) highestOneBit} and
  43  * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
  44  * based on material from Henry S. Warren, Jr.'s <i>Hacker's
  45  * Delight</i>, (Addison Wesley, 2002).
  46  *
  47  * @author  Lee Boynton
  48  * @author  Arthur van Hoff
  49  * @author  Josh Bloch
  50  * @author  Joseph D. Darcy
  51  * @since 1.0
  52  */
  53 public final class Integer extends Number implements Comparable<Integer> {
  54     /**
  55      * A constant holding the minimum value an {@code int} can
  56      * have, -2<sup>31</sup>.
  57      */
  58     @Native public static final int   MIN_VALUE = 0x80000000;
  59 
  60     /**
  61      * A constant holding the maximum value an {@code int} can
  62      * have, 2<sup>31</sup>-1.
  63      */
  64     @Native public static final int   MAX_VALUE = 0x7fffffff;
  65 
  66     /**
  67      * The {@code Class} instance representing the primitive type
  68      * {@code int}.
  69      *
  70      * @since   1.1
  71      */
  72     @SuppressWarnings("unchecked")
  73     public static final Class<Integer>  TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
  74 
  75     /**
  76      * All possible chars for representing a number as a String
  77      */
  78     final static char[] digits = {
  79         '0' , '1' , '2' , '3' , '4' , '5' ,
  80         '6' , '7' , '8' , '9' , 'a' , 'b' ,
  81         'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
  82         'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
  83         'o' , 'p' , 'q' , 'r' , 's' , 't' ,
  84         'u' , 'v' , 'w' , 'x' , 'y' , 'z'
  85     };
  86 
  87     /**
  88      * Returns a string representation of the first argument in the
  89      * radix specified by the second argument.
  90      *
  91      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
  92      * or larger than {@code Character.MAX_RADIX}, then the radix
  93      * {@code 10} is used instead.
  94      *
  95      * <p>If the first argument is negative, the first element of the
  96      * result is the ASCII minus character {@code '-'}
  97      * ({@code '\u005Cu002D'}). If the first argument is not
  98      * negative, no sign character appears in the result.
  99      *
 100      * <p>The remaining characters of the result represent the magnitude
 101      * of the first argument. If the magnitude is zero, it is
 102      * represented by a single zero character {@code '0'}
 103      * ({@code '\u005Cu0030'}); otherwise, the first character of
 104      * the representation of the magnitude will not be the zero
 105      * character.  The following ASCII characters are used as digits:
 106      *
 107      * <blockquote>
 108      *   {@code 0123456789abcdefghijklmnopqrstuvwxyz}
 109      * </blockquote>
 110      *
 111      * These are {@code '\u005Cu0030'} through
 112      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 113      * {@code '\u005Cu007A'}. If {@code radix} is
 114      * <var>N</var>, then the first <var>N</var> of these characters
 115      * are used as radix-<var>N</var> digits in the order shown. Thus,
 116      * the digits for hexadecimal (radix 16) are
 117      * {@code 0123456789abcdef}. If uppercase letters are
 118      * desired, the {@link java.lang.String#toUpperCase()} method may
 119      * be called on the result:
 120      *
 121      * <blockquote>
 122      *  {@code Integer.toString(n, 16).toUpperCase()}
 123      * </blockquote>
 124      *
 125      * @param   i       an integer to be converted to a string.
 126      * @param   radix   the radix to use in the string representation.
 127      * @return  a string representation of the argument in the specified radix.
 128      * @see     java.lang.Character#MAX_RADIX
 129      * @see     java.lang.Character#MIN_RADIX
 130      */
 131     public static String toString(int i, int radix) {
 132         if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
 133             radix = 10;
 134 
 135         /* Use the faster version */
 136         if (radix == 10) {
 137             return toString(i);
 138         }
 139 
 140         char buf[] = new char[33];
 141         boolean negative = (i < 0);
 142         int charPos = 32;
 143 
 144         if (!negative) {
 145             i = -i;
 146         }
 147 
 148         while (i <= -radix) {
 149             buf[charPos--] = digits[-(i % radix)];
 150             i = i / radix;
 151         }
 152         buf[charPos] = digits[-i];
 153 
 154         if (negative) {
 155             buf[--charPos] = '-';
 156         }
 157 
 158         return new String(buf, charPos, (33 - charPos));
 159     }
 160 
 161     /**
 162      * Returns a string representation of the first argument as an
 163      * unsigned integer value in the radix specified by the second
 164      * argument.
 165      *
 166      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
 167      * or larger than {@code Character.MAX_RADIX}, then the radix
 168      * {@code 10} is used instead.
 169      *
 170      * <p>Note that since the first argument is treated as an unsigned
 171      * value, no leading sign character is printed.
 172      *
 173      * <p>If the magnitude is zero, it is represented by a single zero
 174      * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
 175      * the first character of the representation of the magnitude will
 176      * not be the zero character.
 177      *
 178      * <p>The behavior of radixes and the characters used as digits
 179      * are the same as {@link #toString(int, int) toString}.
 180      *
 181      * @param   i       an integer to be converted to an unsigned string.
 182      * @param   radix   the radix to use in the string representation.
 183      * @return  an unsigned string representation of the argument in the specified radix.
 184      * @see     #toString(int, int)
 185      * @since 1.8
 186      */
 187     public static String toUnsignedString(int i, int radix) {
 188         return Long.toUnsignedString(toUnsignedLong(i), radix);
 189     }
 190 
 191     /**
 192      * Returns a string representation of the integer argument as an
 193      * unsigned integer in base&nbsp;16.
 194      *
 195      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 196      * if the argument is negative; otherwise, it is equal to the
 197      * argument.  This value is converted to a string of ASCII digits
 198      * in hexadecimal (base&nbsp;16) with no extra leading
 199      * {@code 0}s.
 200      *
 201      * <p>The value of the argument can be recovered from the returned
 202      * string {@code s} by calling {@link
 203      * Integer#parseUnsignedInt(String, int)
 204      * Integer.parseUnsignedInt(s, 16)}.
 205      *
 206      * <p>If the unsigned magnitude is zero, it is represented by a
 207      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 208      * otherwise, the first character of the representation of the
 209      * unsigned magnitude will not be the zero character. The
 210      * following characters are used as hexadecimal digits:
 211      *
 212      * <blockquote>
 213      *  {@code 0123456789abcdef}
 214      * </blockquote>
 215      *
 216      * These are the characters {@code '\u005Cu0030'} through
 217      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 218      * {@code '\u005Cu0066'}. If uppercase letters are
 219      * desired, the {@link java.lang.String#toUpperCase()} method may
 220      * be called on the result:
 221      *
 222      * <blockquote>
 223      *  {@code Integer.toHexString(n).toUpperCase()}
 224      * </blockquote>
 225      *
 226      * @param   i   an integer to be converted to a string.
 227      * @return  the string representation of the unsigned integer value
 228      *          represented by the argument in hexadecimal (base&nbsp;16).
 229      * @see #parseUnsignedInt(String, int)
 230      * @see #toUnsignedString(int, int)
 231      * @since   1.0.2
 232      */
 233     public static String toHexString(int i) {
 234         return toUnsignedString0(i, 4);
 235     }
 236 
 237     /**
 238      * Returns a string representation of the integer argument as an
 239      * unsigned integer in base&nbsp;8.
 240      *
 241      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 242      * if the argument is negative; otherwise, it is equal to the
 243      * argument.  This value is converted to a string of ASCII digits
 244      * in octal (base&nbsp;8) with no extra leading {@code 0}s.
 245      *
 246      * <p>The value of the argument can be recovered from the returned
 247      * string {@code s} by calling {@link
 248      * Integer#parseUnsignedInt(String, int)
 249      * Integer.parseUnsignedInt(s, 8)}.
 250      *
 251      * <p>If the unsigned magnitude is zero, it is represented by a
 252      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 253      * otherwise, the first character of the representation of the
 254      * unsigned magnitude will not be the zero character. The
 255      * following characters are used as octal digits:
 256      *
 257      * <blockquote>
 258      * {@code 01234567}
 259      * </blockquote>
 260      *
 261      * These are the characters {@code '\u005Cu0030'} through
 262      * {@code '\u005Cu0037'}.
 263      *
 264      * @param   i   an integer to be converted to a string.
 265      * @return  the string representation of the unsigned integer value
 266      *          represented by the argument in octal (base&nbsp;8).
 267      * @see #parseUnsignedInt(String, int)
 268      * @see #toUnsignedString(int, int)
 269      * @since   1.0.2
 270      */
 271     public static String toOctalString(int i) {
 272         return toUnsignedString0(i, 3);
 273     }
 274 
 275     /**
 276      * Returns a string representation of the integer argument as an
 277      * unsigned integer in base&nbsp;2.
 278      *
 279      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 280      * if the argument is negative; otherwise it is equal to the
 281      * argument.  This value is converted to a string of ASCII digits
 282      * in binary (base&nbsp;2) with no extra leading {@code 0}s.
 283      *
 284      * <p>The value of the argument can be recovered from the returned
 285      * string {@code s} by calling {@link
 286      * Integer#parseUnsignedInt(String, int)
 287      * Integer.parseUnsignedInt(s, 2)}.
 288      *
 289      * <p>If the unsigned magnitude is zero, it is represented by a
 290      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 291      * otherwise, the first character of the representation of the
 292      * unsigned magnitude will not be the zero character. The
 293      * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
 294      * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
 295      *
 296      * @param   i   an integer to be converted to a string.
 297      * @return  the string representation of the unsigned integer value
 298      *          represented by the argument in binary (base&nbsp;2).
 299      * @see #parseUnsignedInt(String, int)
 300      * @see #toUnsignedString(int, int)
 301      * @since   1.0.2
 302      */
 303     public static String toBinaryString(int i) {
 304         return toUnsignedString0(i, 1);
 305     }
 306 
 307     /**
 308      * Convert the integer to an unsigned number.
 309      */
 310     private static String toUnsignedString0(int val, int shift) {
 311         // assert shift > 0 && shift <=5 : "Illegal shift value";
 312         int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
 313         int chars = Math.max(((mag + (shift - 1)) / shift), 1);
 314         char[] buf = new char[chars];
 315 
 316         formatUnsignedInt(val, shift, buf, 0, chars);
 317 
 318         // Use special constructor which takes over "buf".
 319         return new String(buf, true);
 320     }
 321 
 322     /**
 323      * Format an {@code int} (treated as unsigned) into a character buffer. If
 324      * {@code len} exceeds the formatted ASCII representation of {@code val},
 325      * {@code buf} will be padded with leading zeroes.
 326      *
 327      * @param val the unsigned int to format
 328      * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
 329      * @param buf the character buffer to write to
 330      * @param offset the offset in the destination buffer to start at
 331      * @param len the number of characters to write
 332      */
 333      static void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
 334         // assert shift > 0 && shift <=5 : "Illegal shift value";
 335         // assert offset >= 0 && offset < buf.length : "illegal offset";
 336         // assert len > 0 && (offset + len) <= buf.length : "illegal length";
 337         int charPos = offset + len;
 338         int radix = 1 << shift;
 339         int mask = radix - 1;
 340         do {
 341             buf[--charPos] = Integer.digits[val & mask];
 342             val >>>= shift;
 343         } while (charPos > offset);
 344     }
 345 
 346     final static char [] DigitTens = {
 347         '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
 348         '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
 349         '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
 350         '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
 351         '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
 352         '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
 353         '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
 354         '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
 355         '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
 356         '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
 357         } ;
 358 
 359     final static char [] DigitOnes = {
 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         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 367         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 368         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 369         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 370         } ;
 371 
 372         // I use the "invariant division by multiplication" trick to
 373         // accelerate Integer.toString.  In particular we want to
 374         // avoid division by 10.
 375         //
 376         // The "trick" has roughly the same performance characteristics
 377         // as the "classic" Integer.toString code on a non-JIT VM.
 378         // The trick avoids .rem and .div calls but has a longer code
 379         // path and is thus dominated by dispatch overhead.  In the
 380         // JIT case the dispatch overhead doesn't exist and the
 381         // "trick" is considerably faster than the classic code.
 382         //
 383         // RE:  Division by Invariant Integers using Multiplication
 384         //      T Gralund, P Montgomery
 385         //      ACM PLDI 1994
 386         //
 387 
 388     /**
 389      * Returns a {@code String} object representing the
 390      * specified integer. The argument is converted to signed decimal
 391      * representation and returned as a string, exactly as if the
 392      * argument and radix 10 were given as arguments to the {@link
 393      * #toString(int, int)} method.
 394      *
 395      * @param   i   an integer to be converted.
 396      * @return  a string representation of the argument in base&nbsp;10.
 397      */
 398     public static String toString(int i) {
 399         if (i == Integer.MIN_VALUE)
 400             return "-2147483648";
 401         int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
 402         char[] buf = new char[size];
 403         getChars(i, size, buf);
 404         return new String(buf, true);
 405     }
 406 
 407     /**
 408      * Returns a string representation of the argument as an unsigned
 409      * decimal value.
 410      *
 411      * The argument is converted to unsigned decimal representation
 412      * and returned as a string exactly as if the argument and radix
 413      * 10 were given as arguments to the {@link #toUnsignedString(int,
 414      * int)} method.
 415      *
 416      * @param   i  an integer to be converted to an unsigned string.
 417      * @return  an unsigned string representation of the argument.
 418      * @see     #toUnsignedString(int, int)
 419      * @since 1.8
 420      */
 421     public static String toUnsignedString(int i) {
 422         return Long.toString(toUnsignedLong(i));
 423     }
 424 
 425     /**
 426      * Places characters representing the integer i into the
 427      * character array buf. The characters are placed into
 428      * the buffer backwards starting with the least significant
 429      * digit at the specified index (exclusive), and working
 430      * backwards from there.
 431      *
 432      * Will fail if i == Integer.MIN_VALUE
 433      */
 434     static void getChars(int i, int index, char[] buf) {
 435         int q, r;
 436         int charPos = index;
 437         char sign = 0;
 438 
 439         if (i < 0) {
 440             sign = '-';
 441             i = -i;
 442         }
 443 
 444         // Generate two digits per iteration
 445         while (i >= 65536) {
 446             q = i / 100;
 447         // really: r = i - (q * 100);
 448             r = i - ((q << 6) + (q << 5) + (q << 2));
 449             i = q;
 450             buf [--charPos] = DigitOnes[r];
 451             buf [--charPos] = DigitTens[r];
 452         }
 453 
 454         // Fall thru to fast mode for smaller numbers
 455         // assert(i <= 65536, i);
 456         for (;;) {
 457             q = (i * 52429) >>> (16+3);
 458             r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...
 459             buf [--charPos] = digits [r];
 460             i = q;
 461             if (i == 0) break;
 462         }
 463         if (sign != 0) {
 464             buf [--charPos] = sign;
 465         }
 466     }
 467 
 468     final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
 469                                       99999999, 999999999, Integer.MAX_VALUE };
 470 
 471     // Requires positive x
 472     static int stringSize(int x) {
 473         for (int i=0; ; i++)
 474             if (x <= sizeTable[i])
 475                 return i+1;
 476     }
 477 
 478     /**
 479      * Parses the string argument as a signed integer in the radix
 480      * specified by the second argument. The characters in the string
 481      * must all be digits of the specified radix (as determined by
 482      * whether {@link java.lang.Character#digit(char, int)} returns a
 483      * nonnegative value), except that the first character may be an
 484      * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
 485      * indicate a negative value or an ASCII plus sign {@code '+'}
 486      * ({@code '\u005Cu002B'}) to indicate a positive value. The
 487      * resulting integer value is returned.
 488      *
 489      * <p>An exception of type {@code NumberFormatException} is
 490      * thrown if any of the following situations occurs:
 491      * <ul>
 492      * <li>The first argument is {@code null} or is a string of
 493      * length zero.
 494      *
 495      * <li>The radix is either smaller than
 496      * {@link java.lang.Character#MIN_RADIX} or
 497      * larger than {@link java.lang.Character#MAX_RADIX}.
 498      *
 499      * <li>Any character of the string is not a digit of the specified
 500      * radix, except that the first character may be a minus sign
 501      * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
 502      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 503      * string is longer than length 1.
 504      *
 505      * <li>The value represented by the string is not a value of type
 506      * {@code int}.
 507      * </ul>
 508      *
 509      * <p>Examples:
 510      * <blockquote><pre>
 511      * parseInt("0", 10) returns 0
 512      * parseInt("473", 10) returns 473
 513      * parseInt("+42", 10) returns 42
 514      * parseInt("-0", 10) returns 0
 515      * parseInt("-FF", 16) returns -255
 516      * parseInt("1100110", 2) returns 102
 517      * parseInt("2147483647", 10) returns 2147483647
 518      * parseInt("-2147483648", 10) returns -2147483648
 519      * parseInt("2147483648", 10) throws a NumberFormatException
 520      * parseInt("99", 8) throws a NumberFormatException
 521      * parseInt("Kona", 10) throws a NumberFormatException
 522      * parseInt("Kona", 27) returns 411787
 523      * </pre></blockquote>
 524      *
 525      * @param      s   the {@code String} containing the integer
 526      *                  representation to be parsed
 527      * @param      radix   the radix to be used while parsing {@code s}.
 528      * @return     the integer represented by the string argument in the
 529      *             specified radix.
 530      * @exception  NumberFormatException if the {@code String}
 531      *             does not contain a parsable {@code int}.
 532      */
 533     public static int parseInt(String s, int radix)
 534                 throws NumberFormatException
 535     {
 536         /*
 537          * WARNING: This method may be invoked early during VM initialization
 538          * before IntegerCache is initialized. Care must be taken to not use
 539          * the valueOf method.
 540          */
 541 
 542         if (s == null) {
 543             throw new NumberFormatException("null");
 544         }
 545 
 546         if (radix < Character.MIN_RADIX) {
 547             throw new NumberFormatException("radix " + radix +
 548                                             " less than Character.MIN_RADIX");
 549         }
 550 
 551         if (radix > Character.MAX_RADIX) {
 552             throw new NumberFormatException("radix " + radix +
 553                                             " greater than Character.MAX_RADIX");
 554         }
 555 
 556         boolean negative = false;
 557         int i = 0, len = s.length();
 558         int limit = -Integer.MAX_VALUE;
 559 
 560         if (len > 0) {
 561             char firstChar = s.charAt(0);
 562             if (firstChar < '0') { // Possible leading "+" or "-"
 563                 if (firstChar == '-') {
 564                     negative = true;
 565                     limit = Integer.MIN_VALUE;
 566                 } else if (firstChar != '+') {
 567                     throw NumberFormatException.forInputString(s);
 568                 }
 569 
 570                 if (len == 1) { // Cannot have lone "+" or "-"
 571                     throw NumberFormatException.forInputString(s);
 572                 }
 573                 i++;
 574             }
 575             int multmin = limit / radix;
 576             int result = 0;
 577             while (i < len) {
 578                 // Accumulating negatively avoids surprises near MAX_VALUE
 579                 int digit = Character.digit(s.charAt(i++), radix);
 580                 if (digit < 0 || result < multmin) {
 581                     throw NumberFormatException.forInputString(s);
 582                 }
 583                 result *= radix;
 584                 if (result < limit + digit) {
 585                     throw NumberFormatException.forInputString(s);
 586                 }
 587                 result -= digit;
 588             }
 589             return negative ? result : -result;
 590         } else {
 591             throw NumberFormatException.forInputString(s);
 592         }
 593     }
 594 
 595     /**
 596      * Parses the {@link CharSequence} argument as a signed {@code int} in the
 597      * specified {@code radix}, beginning at the specified {@code beginIndex}
 598      * and extending to {@code endIndex - 1}.
 599      *
 600      * <p>The method does not take steps to guard against the
 601      * {@code CharSequence} being mutated while parsing.
 602      *
 603      * @param      s   the {@code CharSequence} containing the {@code int}
 604      *                  representation to be parsed
 605      * @param      beginIndex   the beginning index, inclusive.
 606      * @param      endIndex     the ending index, exclusive.
 607      * @param      radix   the radix to be used while parsing {@code s}.
 608      * @return     the signed {@code int} represented by the subsequence in
 609      *             the specified radix.
 610      * @throws     NullPointerException  if {@code s} is null.
 611      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 612      *             negative, or if {@code beginIndex} is greater than
 613      *             {@code endIndex} or if {@code endIndex} is greater than
 614      *             {@code s.length()}.
 615      * @throws     NumberFormatException  if the {@code CharSequence} does not
 616      *             contain a parsable {@code int} in the specified
 617      *             {@code radix}, or if {@code radix} is either smaller than
 618      *             {@link java.lang.Character#MIN_RADIX} or larger than
 619      *             {@link java.lang.Character#MAX_RADIX}.
 620      * @since  1.9
 621      */
 622     public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix)
 623                 throws NumberFormatException {
 624         s = Objects.requireNonNull(s);
 625 
 626         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 627             throw new IndexOutOfBoundsException();
 628         }
 629         if (radix < Character.MIN_RADIX) {
 630             throw new NumberFormatException("radix " + radix +
 631                                             " less than Character.MIN_RADIX");
 632         }
 633         if (radix > Character.MAX_RADIX) {
 634             throw new NumberFormatException("radix " + radix +
 635                                             " greater than Character.MAX_RADIX");
 636         }
 637 
 638         boolean negative = false;
 639         int i = beginIndex;
 640         int limit = -Integer.MAX_VALUE;
 641 
 642         if (i < endIndex) {
 643             char firstChar = s.charAt(i);
 644             if (firstChar < '0') { // Possible leading "+" or "-"
 645                 if (firstChar == '-') {
 646                     negative = true;
 647                     limit = Integer.MIN_VALUE;
 648                 } else if (firstChar != '+') {
 649                     throw NumberFormatException.forCharSequence(s, beginIndex,
 650                             endIndex, i);
 651                 }
 652                 i++;
 653                 if (i == endIndex) { // Cannot have lone "+" or "-"
 654                     throw NumberFormatException.forCharSequence(s, beginIndex,
 655                             endIndex, i);
 656                 }
 657             }
 658             int multmin = limit / radix;
 659             int result = 0;
 660             while (i < endIndex) {
 661                 // Accumulating negatively avoids surprises near MAX_VALUE
 662                 int digit = Character.digit(s.charAt(i), radix);
 663                 if (digit < 0 || result < multmin) {
 664                     throw NumberFormatException.forCharSequence(s, beginIndex,
 665                             endIndex, i);
 666                 }
 667                 result *= radix;
 668                 if (result < limit + digit) {
 669                     throw NumberFormatException.forCharSequence(s, beginIndex,
 670                             endIndex, i);
 671                 }
 672                 i++;
 673                 result -= digit;
 674             }
 675             return negative ? result : -result;
 676         } else {
 677             throw NumberFormatException.forInputString("");
 678         }
 679     }
 680 
 681     /**
 682      * Parses the string argument as a signed decimal integer. The
 683      * characters in the string must all be decimal digits, except
 684      * that the first character may be an ASCII minus sign {@code '-'}
 685      * ({@code '\u005Cu002D'}) to indicate a negative value or an
 686      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
 687      * indicate a positive value. The resulting integer value is
 688      * returned, exactly as if the argument and the radix 10 were
 689      * given as arguments to the {@link #parseInt(java.lang.String,
 690      * int)} method.
 691      *
 692      * @param s    a {@code String} containing the {@code int}
 693      *             representation to be parsed
 694      * @return     the integer value represented by the argument in decimal.
 695      * @exception  NumberFormatException  if the string does not contain a
 696      *               parsable integer.
 697      */
 698     public static int parseInt(String s) throws NumberFormatException {
 699         return parseInt(s,10);
 700     }
 701 
 702     /**
 703      * Parses the string argument as an unsigned integer in the radix
 704      * specified by the second argument.  An unsigned integer maps the
 705      * values usually associated with negative numbers to positive
 706      * numbers larger than {@code MAX_VALUE}.
 707      *
 708      * The characters in the string must all be digits of the
 709      * specified radix (as determined by whether {@link
 710      * java.lang.Character#digit(char, int)} returns a nonnegative
 711      * value), except that the first character may be an ASCII plus
 712      * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
 713      * integer value is returned.
 714      *
 715      * <p>An exception of type {@code NumberFormatException} is
 716      * thrown if any of the following situations occurs:
 717      * <ul>
 718      * <li>The first argument is {@code null} or is a string of
 719      * length zero.
 720      *
 721      * <li>The radix is either smaller than
 722      * {@link java.lang.Character#MIN_RADIX} or
 723      * larger than {@link java.lang.Character#MAX_RADIX}.
 724      *
 725      * <li>Any character of the string is not a digit of the specified
 726      * radix, except that the first character may be a plus sign
 727      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 728      * string is longer than length 1.
 729      *
 730      * <li>The value represented by the string is larger than the
 731      * largest unsigned {@code int}, 2<sup>32</sup>-1.
 732      *
 733      * </ul>
 734      *
 735      *
 736      * @param      s   the {@code String} containing the unsigned integer
 737      *                  representation to be parsed
 738      * @param      radix   the radix to be used while parsing {@code s}.
 739      * @return     the integer represented by the string argument in the
 740      *             specified radix.
 741      * @throws     NumberFormatException if the {@code String}
 742      *             does not contain a parsable {@code int}.
 743      * @since 1.8
 744      */
 745     public static int parseUnsignedInt(String s, int radix)
 746                 throws NumberFormatException {
 747         if (s == null)  {
 748             throw new NumberFormatException("null");
 749         }
 750 
 751         int len = s.length();
 752         if (len > 0) {
 753             char firstChar = s.charAt(0);
 754             if (firstChar == '-') {
 755                 throw new
 756                     NumberFormatException(String.format("Illegal leading minus sign " +
 757                                                        "on unsigned string %s.", s));
 758             } else {
 759                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 760                     (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
 761                     return parseInt(s, radix);
 762                 } else {
 763                     long ell = Long.parseLong(s, radix);
 764                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 765                         return (int) ell;
 766                     } else {
 767                         throw new
 768                             NumberFormatException(String.format("String value %s exceeds " +
 769                                                                 "range of unsigned int.", s));
 770                     }
 771                 }
 772             }
 773         } else {
 774             throw NumberFormatException.forInputString(s);
 775         }
 776     }
 777 
 778     /**
 779      * Parses the {@link CharSequence} argument as an unsigned {@code int} in
 780      * the specified {@code radix}, beginning at the specified
 781      * {@code beginIndex} and extending to {@code endIndex - 1}.
 782      *
 783      * <p>The method does not take steps to guard against the
 784      * {@code CharSequence} being mutated while parsing.
 785      *
 786      * @param      s   the {@code CharSequence} containing the unsigned
 787      *                 {@code int} representation to be parsed
 788      * @param      beginIndex   the beginning index, inclusive.
 789      * @param      endIndex     the ending index, exclusive.
 790      * @param      radix   the radix to be used while parsing {@code s}.
 791      * @return     the unsigned {@code int} represented by the subsequence in
 792      *             the specified radix.
 793      * @throws     NullPointerException  if {@code s} is null.
 794      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 795      *             negative, or if {@code beginIndex} is greater than
 796      *             {@code endIndex} or if {@code endIndex} is greater than
 797      *             {@code s.length()}.
 798      * @throws     NumberFormatException  if the {@code CharSequence} does not
 799      *             contain a parsable unsigned {@code int} in the specified
 800      *             {@code radix}, or if {@code radix} is either smaller than
 801      *             {@link java.lang.Character#MIN_RADIX} or larger than
 802      *             {@link java.lang.Character#MAX_RADIX}.
 803      * @since  1.9
 804      */
 805     public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix)
 806                 throws NumberFormatException {
 807         s = Objects.requireNonNull(s);
 808 
 809         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 810             throw new IndexOutOfBoundsException();
 811         }
 812         int start = beginIndex, len = endIndex - beginIndex;
 813 
 814         if (len > 0) {
 815             char firstChar = s.charAt(start);
 816             if (firstChar == '-') {
 817                 throw new
 818                     NumberFormatException(String.format("Illegal leading minus sign " +
 819                                                        "on unsigned string %s.", s));
 820             } else {
 821                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 822                         (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits
 823                     return parseInt(s, start, start + len, radix);
 824                 } else {
 825                     long ell = Long.parseLong(s, start, start + len, radix);
 826                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 827                         return (int) ell;
 828                     } else {
 829                         throw new
 830                             NumberFormatException(String.format("String value %s exceeds " +
 831                                                                 "range of unsigned int.", s));
 832                     }
 833                 }
 834             }
 835         } else {
 836             throw new NumberFormatException("");
 837         }
 838     }
 839 
 840     /**
 841      * Parses the string argument as an unsigned decimal integer. The
 842      * characters in the string must all be decimal digits, except
 843      * that the first character may be an ASCII plus sign {@code
 844      * '+'} ({@code '\u005Cu002B'}). The resulting integer value
 845      * is returned, exactly as if the argument and the radix 10 were
 846      * given as arguments to the {@link
 847      * #parseUnsignedInt(java.lang.String, int)} method.
 848      *
 849      * @param s   a {@code String} containing the unsigned {@code int}
 850      *            representation to be parsed
 851      * @return    the unsigned integer value represented by the argument in decimal.
 852      * @throws    NumberFormatException  if the string does not contain a
 853      *            parsable unsigned integer.
 854      * @since 1.8
 855      */
 856     public static int parseUnsignedInt(String s) throws NumberFormatException {
 857         return parseUnsignedInt(s, 10);
 858     }
 859 
 860     /**
 861      * Returns an {@code Integer} object holding the value
 862      * extracted from the specified {@code String} when parsed
 863      * with the radix given by the second argument. The first argument
 864      * is interpreted as representing a signed integer in the radix
 865      * specified by the second argument, exactly as if the arguments
 866      * were given to the {@link #parseInt(java.lang.String, int)}
 867      * method. The result is an {@code Integer} object that
 868      * represents the integer value specified by the string.
 869      *
 870      * <p>In other words, this method returns an {@code Integer}
 871      * object equal to the value of:
 872      *
 873      * <blockquote>
 874      *  {@code new Integer(Integer.parseInt(s, radix))}
 875      * </blockquote>
 876      *
 877      * @param      s   the string to be parsed.
 878      * @param      radix the radix to be used in interpreting {@code s}
 879      * @return     an {@code Integer} object holding the value
 880      *             represented by the string argument in the specified
 881      *             radix.
 882      * @exception NumberFormatException if the {@code String}
 883      *            does not contain a parsable {@code int}.
 884      */
 885     public static Integer valueOf(String s, int radix) throws NumberFormatException {
 886         return Integer.valueOf(parseInt(s,radix));
 887     }
 888 
 889     /**
 890      * Returns an {@code Integer} object holding the
 891      * value of the specified {@code String}. The argument is
 892      * interpreted as representing a signed decimal integer, exactly
 893      * as if the argument were given to the {@link
 894      * #parseInt(java.lang.String)} method. The result is an
 895      * {@code Integer} object that represents the integer value
 896      * specified by the string.
 897      *
 898      * <p>In other words, this method returns an {@code Integer}
 899      * object equal to the value of:
 900      *
 901      * <blockquote>
 902      *  {@code new Integer(Integer.parseInt(s))}
 903      * </blockquote>
 904      *
 905      * @param      s   the string to be parsed.
 906      * @return     an {@code Integer} object holding the value
 907      *             represented by the string argument.
 908      * @exception  NumberFormatException  if the string cannot be parsed
 909      *             as an integer.
 910      */
 911     public static Integer valueOf(String s) throws NumberFormatException {
 912         return Integer.valueOf(parseInt(s, 10));
 913     }
 914 
 915     /**
 916      * Cache to support the object identity semantics of autoboxing for values between
 917      * -128 and 127 (inclusive) as required by JLS.
 918      *
 919      * The cache is initialized on first usage.  The size of the cache
 920      * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
 921      * During VM initialization, java.lang.Integer.IntegerCache.high property
 922      * may be set and saved in the private system properties in the
 923      * sun.misc.VM class.
 924      */
 925 
 926     private static class IntegerCache {
 927         static final int low = -128;
 928         static final int high;
 929         static final Integer cache[];
 930 
 931         static {
 932             // high value may be configured by property
 933             int h = 127;
 934             String integerCacheHighPropValue =
 935                 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
 936             if (integerCacheHighPropValue != null) {
 937                 try {
 938                     int i = parseInt(integerCacheHighPropValue);
 939                     i = Math.max(i, 127);
 940                     // Maximum array size is Integer.MAX_VALUE
 941                     h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
 942                 } catch( NumberFormatException nfe) {
 943                     // If the property cannot be parsed into an int, ignore it.
 944                 }
 945             }
 946             high = h;
 947 
 948             cache = new Integer[(high - low) + 1];
 949             int j = low;
 950             for(int k = 0; k < cache.length; k++)
 951                 cache[k] = new Integer(j++);
 952 
 953             // range [-128, 127] must be interned (JLS7 5.1.7)
 954             assert IntegerCache.high >= 127;
 955         }
 956 
 957         private IntegerCache() {}
 958     }
 959 
 960     /**
 961      * Returns an {@code Integer} instance representing the specified
 962      * {@code int} value.  If a new {@code Integer} instance is not
 963      * required, this method should generally be used in preference to
 964      * the constructor {@link #Integer(int)}, as this method is likely
 965      * to yield significantly better space and time performance by
 966      * caching frequently requested values.
 967      *
 968      * This method will always cache values in the range -128 to 127,
 969      * inclusive, and may cache other values outside of this range.
 970      *
 971      * @param  i an {@code int} value.
 972      * @return an {@code Integer} instance representing {@code i}.
 973      * @since  1.5
 974      */
 975     public static Integer valueOf(int i) {
 976         if (i >= IntegerCache.low && i <= IntegerCache.high)
 977             return IntegerCache.cache[i + (-IntegerCache.low)];
 978         return new Integer(i);
 979     }
 980 
 981     /**
 982      * The value of the {@code Integer}.
 983      *
 984      * @serial
 985      */
 986     private final int value;
 987 
 988     /**
 989      * Constructs a newly allocated {@code Integer} object that
 990      * represents the specified {@code int} value.
 991      *
 992      * @param   value   the value to be represented by the
 993      *                  {@code Integer} object.
 994      */
 995     public Integer(int value) {
 996         this.value = value;
 997     }
 998 
 999     /**
1000      * Constructs a newly allocated {@code Integer} object that
1001      * represents the {@code int} value indicated by the
1002      * {@code String} parameter. The string is converted to an
1003      * {@code int} value in exactly the manner used by the
1004      * {@code parseInt} method for radix 10.
1005      *
1006      * @param      s   the {@code String} to be converted to an
1007      *                 {@code Integer}.
1008      * @exception  NumberFormatException  if the {@code String} does not
1009      *               contain a parsable integer.
1010      * @see        java.lang.Integer#parseInt(java.lang.String, int)
1011      */
1012     public Integer(String s) throws NumberFormatException {
1013         this.value = parseInt(s, 10);
1014     }
1015 
1016     /**
1017      * Returns the value of this {@code Integer} as a {@code byte}
1018      * after a narrowing primitive conversion.
1019      * @jls 5.1.3 Narrowing Primitive Conversions
1020      */
1021     public byte byteValue() {
1022         return (byte)value;
1023     }
1024 
1025     /**
1026      * Returns the value of this {@code Integer} as a {@code short}
1027      * after a narrowing primitive conversion.
1028      * @jls 5.1.3 Narrowing Primitive Conversions
1029      */
1030     public short shortValue() {
1031         return (short)value;
1032     }
1033 
1034     /**
1035      * Returns the value of this {@code Integer} as an
1036      * {@code int}.
1037      */
1038     public int intValue() {
1039         return value;
1040     }
1041 
1042     /**
1043      * Returns the value of this {@code Integer} as a {@code long}
1044      * after a widening primitive conversion.
1045      * @jls 5.1.2 Widening Primitive Conversions
1046      * @see Integer#toUnsignedLong(int)
1047      */
1048     public long longValue() {
1049         return (long)value;
1050     }
1051 
1052     /**
1053      * Returns the value of this {@code Integer} as a {@code float}
1054      * after a widening primitive conversion.
1055      * @jls 5.1.2 Widening Primitive Conversions
1056      */
1057     public float floatValue() {
1058         return (float)value;
1059     }
1060 
1061     /**
1062      * Returns the value of this {@code Integer} as a {@code double}
1063      * after a widening primitive conversion.
1064      * @jls 5.1.2 Widening Primitive Conversions
1065      */
1066     public double doubleValue() {
1067         return (double)value;
1068     }
1069 
1070     /**
1071      * Returns a {@code String} object representing this
1072      * {@code Integer}'s value. The value is converted to signed
1073      * decimal representation and returned as a string, exactly as if
1074      * the integer value were given as an argument to the {@link
1075      * java.lang.Integer#toString(int)} method.
1076      *
1077      * @return  a string representation of the value of this object in
1078      *          base&nbsp;10.
1079      */
1080     public String toString() {
1081         return toString(value);
1082     }
1083 
1084     /**
1085      * Returns a hash code for this {@code Integer}.
1086      *
1087      * @return  a hash code value for this object, equal to the
1088      *          primitive {@code int} value represented by this
1089      *          {@code Integer} object.
1090      */
1091     @Override
1092     public int hashCode() {
1093         return Integer.hashCode(value);
1094     }
1095 
1096     /**
1097      * Returns a hash code for a {@code int} value; compatible with
1098      * {@code Integer.hashCode()}.
1099      *
1100      * @param value the value to hash
1101      * @since 1.8
1102      *
1103      * @return a hash code value for a {@code int} value.
1104      */
1105     public static int hashCode(int value) {
1106         return value;
1107     }
1108 
1109     /**
1110      * Compares this object to the specified object.  The result is
1111      * {@code true} if and only if the argument is not
1112      * {@code null} and is an {@code Integer} object that
1113      * contains the same {@code int} value as this object.
1114      *
1115      * @param   obj   the object to compare with.
1116      * @return  {@code true} if the objects are the same;
1117      *          {@code false} otherwise.
1118      */
1119     public boolean equals(Object obj) {
1120         if (obj instanceof Integer) {
1121             return value == ((Integer)obj).intValue();
1122         }
1123         return false;
1124     }
1125 
1126     /**
1127      * Determines the integer value of the system property with the
1128      * specified name.
1129      *
1130      * <p>The first argument is treated as the name of a system
1131      * property.  System properties are accessible through the {@link
1132      * java.lang.System#getProperty(java.lang.String)} method. The
1133      * string value of this property is then interpreted as an integer
1134      * value using the grammar supported by {@link Integer#decode decode} and
1135      * an {@code Integer} object representing this value is returned.
1136      *
1137      * <p>If there is no property with the specified name, if the
1138      * specified name is empty or {@code null}, or if the property
1139      * does not have the correct numeric format, then {@code null} is
1140      * returned.
1141      *
1142      * <p>In other words, this method returns an {@code Integer}
1143      * object equal to the value of:
1144      *
1145      * <blockquote>
1146      *  {@code getInteger(nm, null)}
1147      * </blockquote>
1148      *
1149      * @param   nm   property name.
1150      * @return  the {@code Integer} value of the property.
1151      * @throws  SecurityException for the same reasons as
1152      *          {@link System#getProperty(String) System.getProperty}
1153      * @see     java.lang.System#getProperty(java.lang.String)
1154      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1155      */
1156     public static Integer getInteger(String nm) {
1157         return getInteger(nm, null);
1158     }
1159 
1160     /**
1161      * Determines the integer value of the system property with the
1162      * specified name.
1163      *
1164      * <p>The first argument is treated as the name of a system
1165      * property.  System properties are accessible through the {@link
1166      * java.lang.System#getProperty(java.lang.String)} method. The
1167      * string value of this property is then interpreted as an integer
1168      * value using the grammar supported by {@link Integer#decode decode} and
1169      * an {@code Integer} object representing this value is returned.
1170      *
1171      * <p>The second argument is the default value. An {@code Integer} object
1172      * that represents the value of the second argument is returned if there
1173      * is no property of the specified name, if the property does not have
1174      * the correct numeric format, or if the specified name is empty or
1175      * {@code null}.
1176      *
1177      * <p>In other words, this method returns an {@code Integer} object
1178      * equal to the value of:
1179      *
1180      * <blockquote>
1181      *  {@code getInteger(nm, new Integer(val))}
1182      * </blockquote>
1183      *
1184      * but in practice it may be implemented in a manner such as:
1185      *
1186      * <blockquote><pre>
1187      * Integer result = getInteger(nm, null);
1188      * return (result == null) ? new Integer(val) : result;
1189      * </pre></blockquote>
1190      *
1191      * to avoid the unnecessary allocation of an {@code Integer}
1192      * object when the default value is not needed.
1193      *
1194      * @param   nm   property name.
1195      * @param   val   default value.
1196      * @return  the {@code Integer} value of the property.
1197      * @throws  SecurityException for the same reasons as
1198      *          {@link System#getProperty(String) System.getProperty}
1199      * @see     java.lang.System#getProperty(java.lang.String)
1200      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1201      */
1202     public static Integer getInteger(String nm, int val) {
1203         Integer result = getInteger(nm, null);
1204         return (result == null) ? Integer.valueOf(val) : result;
1205     }
1206 
1207     /**
1208      * Returns the integer value of the system property with the
1209      * specified name.  The first argument is treated as the name of a
1210      * system property.  System properties are accessible through the
1211      * {@link java.lang.System#getProperty(java.lang.String)} method.
1212      * The string value of this property is then interpreted as an
1213      * integer value, as per the {@link Integer#decode decode} method,
1214      * and an {@code Integer} object representing this value is
1215      * returned; in summary:
1216      *
1217      * <ul><li>If the property value begins with the two ASCII characters
1218      *         {@code 0x} or the ASCII character {@code #}, not
1219      *      followed by a minus sign, then the rest of it is parsed as a
1220      *      hexadecimal integer exactly as by the method
1221      *      {@link #valueOf(java.lang.String, int)} with radix 16.
1222      * <li>If the property value begins with the ASCII character
1223      *     {@code 0} followed by another character, it is parsed as an
1224      *     octal integer exactly as by the method
1225      *     {@link #valueOf(java.lang.String, int)} with radix 8.
1226      * <li>Otherwise, the property value is parsed as a decimal integer
1227      * exactly as by the method {@link #valueOf(java.lang.String, int)}
1228      * with radix 10.
1229      * </ul>
1230      *
1231      * <p>The second argument is the default value. The default value is
1232      * returned if there is no property of the specified name, if the
1233      * property does not have the correct numeric format, or if the
1234      * specified name is empty or {@code null}.
1235      *
1236      * @param   nm   property name.
1237      * @param   val   default value.
1238      * @return  the {@code Integer} value of the property.
1239      * @throws  SecurityException for the same reasons as
1240      *          {@link System#getProperty(String) System.getProperty}
1241      * @see     System#getProperty(java.lang.String)
1242      * @see     System#getProperty(java.lang.String, java.lang.String)
1243      */
1244     public static Integer getInteger(String nm, Integer val) {
1245         String v = null;
1246         try {
1247             v = System.getProperty(nm);
1248         } catch (IllegalArgumentException | NullPointerException e) {
1249         }
1250         if (v != null) {
1251             try {
1252                 return Integer.decode(v);
1253             } catch (NumberFormatException e) {
1254             }
1255         }
1256         return val;
1257     }
1258 
1259     /**
1260      * Decodes a {@code String} into an {@code Integer}.
1261      * Accepts decimal, hexadecimal, and octal numbers given
1262      * by the following grammar:
1263      *
1264      * <blockquote>
1265      * <dl>
1266      * <dt><i>DecodableString:</i>
1267      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1268      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1269      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1270      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1271      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1272      *
1273      * <dt><i>Sign:</i>
1274      * <dd>{@code -}
1275      * <dd>{@code +}
1276      * </dl>
1277      * </blockquote>
1278      *
1279      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1280      * are as defined in section 3.10.1 of
1281      * <cite>The Java&trade; Language Specification</cite>,
1282      * except that underscores are not accepted between digits.
1283      *
1284      * <p>The sequence of characters following an optional
1285      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1286      * "{@code #}", or leading zero) is parsed as by the {@code
1287      * Integer.parseInt} method with the indicated radix (10, 16, or
1288      * 8).  This sequence of characters must represent a positive
1289      * value or a {@link NumberFormatException} will be thrown.  The
1290      * result is negated if first character of the specified {@code
1291      * String} is the minus sign.  No whitespace characters are
1292      * permitted in the {@code String}.
1293      *
1294      * @param     nm the {@code String} to decode.
1295      * @return    an {@code Integer} object holding the {@code int}
1296      *             value represented by {@code nm}
1297      * @exception NumberFormatException  if the {@code String} does not
1298      *            contain a parsable integer.
1299      * @see java.lang.Integer#parseInt(java.lang.String, int)
1300      */
1301     public static Integer decode(String nm) throws NumberFormatException {
1302         int radix = 10;
1303         int index = 0;
1304         boolean negative = false;
1305         Integer result;
1306 
1307         if (nm.length() == 0)
1308             throw new NumberFormatException("Zero length string");
1309         char firstChar = nm.charAt(0);
1310         // Handle sign, if present
1311         if (firstChar == '-') {
1312             negative = true;
1313             index++;
1314         } else if (firstChar == '+')
1315             index++;
1316 
1317         // Handle radix specifier, if present
1318         if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1319             index += 2;
1320             radix = 16;
1321         }
1322         else if (nm.startsWith("#", index)) {
1323             index ++;
1324             radix = 16;
1325         }
1326         else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1327             index ++;
1328             radix = 8;
1329         }
1330 
1331         if (nm.startsWith("-", index) || nm.startsWith("+", index))
1332             throw new NumberFormatException("Sign character in wrong position");
1333 
1334         try {
1335             result = Integer.valueOf(nm.substring(index), radix);
1336             result = negative ? Integer.valueOf(-result.intValue()) : result;
1337         } catch (NumberFormatException e) {
1338             // If number is Integer.MIN_VALUE, we'll end up here. The next line
1339             // handles this case, and causes any genuine format error to be
1340             // rethrown.
1341             String constant = negative ? ("-" + nm.substring(index))
1342                                        : nm.substring(index);
1343             result = Integer.valueOf(constant, radix);
1344         }
1345         return result;
1346     }
1347 
1348     /**
1349      * Compares two {@code Integer} objects numerically.
1350      *
1351      * @param   anotherInteger   the {@code Integer} to be compared.
1352      * @return  the value {@code 0} if this {@code Integer} is
1353      *          equal to the argument {@code Integer}; a value less than
1354      *          {@code 0} if this {@code Integer} is numerically less
1355      *          than the argument {@code Integer}; and a value greater
1356      *          than {@code 0} if this {@code Integer} is numerically
1357      *           greater than the argument {@code Integer} (signed
1358      *           comparison).
1359      * @since   1.2
1360      */
1361     public int compareTo(Integer anotherInteger) {
1362         return compare(this.value, anotherInteger.value);
1363     }
1364 
1365     /**
1366      * Compares two {@code int} values numerically.
1367      * The value returned is identical to what would be returned by:
1368      * <pre>
1369      *    Integer.valueOf(x).compareTo(Integer.valueOf(y))
1370      * </pre>
1371      *
1372      * @param  x the first {@code int} to compare
1373      * @param  y the second {@code int} to compare
1374      * @return the value {@code 0} if {@code x == y};
1375      *         a value less than {@code 0} if {@code x < y}; and
1376      *         a value greater than {@code 0} if {@code x > y}
1377      * @since 1.7
1378      */
1379     public static int compare(int x, int y) {
1380         return (x < y) ? -1 : ((x == y) ? 0 : 1);
1381     }
1382 
1383     /**
1384      * Compares two {@code int} values numerically treating the values
1385      * as unsigned.
1386      *
1387      * @param  x the first {@code int} to compare
1388      * @param  y the second {@code int} to compare
1389      * @return the value {@code 0} if {@code x == y}; a value less
1390      *         than {@code 0} if {@code x < y} as unsigned values; and
1391      *         a value greater than {@code 0} if {@code x > y} as
1392      *         unsigned values
1393      * @since 1.8
1394      */
1395     public static int compareUnsigned(int x, int y) {
1396         return compare(x + MIN_VALUE, y + MIN_VALUE);
1397     }
1398 
1399     /**
1400      * Converts the argument to a {@code long} by an unsigned
1401      * conversion.  In an unsigned conversion to a {@code long}, the
1402      * high-order 32 bits of the {@code long} are zero and the
1403      * low-order 32 bits are equal to the bits of the integer
1404      * argument.
1405      *
1406      * Consequently, zero and positive {@code int} values are mapped
1407      * to a numerically equal {@code long} value and negative {@code
1408      * int} values are mapped to a {@code long} value equal to the
1409      * input plus 2<sup>32</sup>.
1410      *
1411      * @param  x the value to convert to an unsigned {@code long}
1412      * @return the argument converted to {@code long} by an unsigned
1413      *         conversion
1414      * @since 1.8
1415      */
1416     public static long toUnsignedLong(int x) {
1417         return ((long) x) & 0xffffffffL;
1418     }
1419 
1420     /**
1421      * Returns the unsigned quotient of dividing the first argument by
1422      * the second where each argument and the result is interpreted as
1423      * an unsigned value.
1424      *
1425      * <p>Note that in two's complement arithmetic, the three other
1426      * basic arithmetic operations of add, subtract, and multiply are
1427      * bit-wise identical if the two operands are regarded as both
1428      * being signed or both being unsigned.  Therefore separate {@code
1429      * addUnsigned}, etc. methods are not provided.
1430      *
1431      * @param dividend the value to be divided
1432      * @param divisor the value doing the dividing
1433      * @return the unsigned quotient of the first argument divided by
1434      * the second argument
1435      * @see #remainderUnsigned
1436      * @since 1.8
1437      */
1438     public static int divideUnsigned(int dividend, int divisor) {
1439         // In lieu of tricky code, for now just use long arithmetic.
1440         return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1441     }
1442 
1443     /**
1444      * Returns the unsigned remainder from dividing the first argument
1445      * by the second where each argument and the result is interpreted
1446      * as an unsigned value.
1447      *
1448      * @param dividend the value to be divided
1449      * @param divisor the value doing the dividing
1450      * @return the unsigned remainder of the first argument divided by
1451      * the second argument
1452      * @see #divideUnsigned
1453      * @since 1.8
1454      */
1455     public static int remainderUnsigned(int dividend, int divisor) {
1456         // In lieu of tricky code, for now just use long arithmetic.
1457         return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1458     }
1459 
1460 
1461     // Bit twiddling
1462 
1463     /**
1464      * The number of bits used to represent an {@code int} value in two's
1465      * complement binary form.
1466      *
1467      * @since 1.5
1468      */
1469     @Native public static final int SIZE = 32;
1470 
1471     /**
1472      * The number of bytes used to represent a {@code int} value in two's
1473      * complement binary form.
1474      *
1475      * @since 1.8
1476      */
1477     public static final int BYTES = SIZE / Byte.SIZE;
1478 
1479     /**
1480      * Returns an {@code int} value with at most a single one-bit, in the
1481      * position of the highest-order ("leftmost") one-bit in the specified
1482      * {@code int} value.  Returns zero if the specified value has no
1483      * one-bits in its two's complement binary representation, that is, if it
1484      * is equal to zero.
1485      *
1486      * @param i the value whose highest one bit is to be computed
1487      * @return an {@code int} value with a single one-bit, in the position
1488      *     of the highest-order one-bit in the specified value, or zero if
1489      *     the specified value is itself equal to zero.
1490      * @since 1.5
1491      */
1492     public static int highestOneBit(int i) {
1493         // HD, Figure 3-1
1494         i |= (i >>  1);
1495         i |= (i >>  2);
1496         i |= (i >>  4);
1497         i |= (i >>  8);
1498         i |= (i >> 16);
1499         return i - (i >>> 1);
1500     }
1501 
1502     /**
1503      * Returns an {@code int} value with at most a single one-bit, in the
1504      * position of the lowest-order ("rightmost") one-bit in the specified
1505      * {@code int} value.  Returns zero if the specified value has no
1506      * one-bits in its two's complement binary representation, that is, if it
1507      * is equal to zero.
1508      *
1509      * @param i the value whose lowest one bit is to be computed
1510      * @return an {@code int} value with a single one-bit, in the position
1511      *     of the lowest-order one-bit in the specified value, or zero if
1512      *     the specified value is itself equal to zero.
1513      * @since 1.5
1514      */
1515     public static int lowestOneBit(int i) {
1516         // HD, Section 2-1
1517         return i & -i;
1518     }
1519 
1520     /**
1521      * Returns the number of zero bits preceding the highest-order
1522      * ("leftmost") one-bit in the two's complement binary representation
1523      * of the specified {@code int} value.  Returns 32 if the
1524      * specified value has no one-bits in its two's complement representation,
1525      * in other words if it is equal to zero.
1526      *
1527      * <p>Note that this method is closely related to the logarithm base 2.
1528      * For all positive {@code int} values x:
1529      * <ul>
1530      * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1531      * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1532      * </ul>
1533      *
1534      * @param i the value whose number of leading zeros is to be computed
1535      * @return the number of zero bits preceding the highest-order
1536      *     ("leftmost") one-bit in the two's complement binary representation
1537      *     of the specified {@code int} value, or 32 if the value
1538      *     is equal to zero.
1539      * @since 1.5
1540      */
1541     public static int numberOfLeadingZeros(int i) {
1542         // HD, Figure 5-6
1543         if (i == 0)
1544             return 32;
1545         int n = 1;
1546         if (i >>> 16 == 0) { n += 16; i <<= 16; }
1547         if (i >>> 24 == 0) { n +=  8; i <<=  8; }
1548         if (i >>> 28 == 0) { n +=  4; i <<=  4; }
1549         if (i >>> 30 == 0) { n +=  2; i <<=  2; }
1550         n -= i >>> 31;
1551         return n;
1552     }
1553 
1554     /**
1555      * Returns the number of zero bits following the lowest-order ("rightmost")
1556      * one-bit in the two's complement binary representation of the specified
1557      * {@code int} value.  Returns 32 if the specified value has no
1558      * one-bits in its two's complement representation, in other words if it is
1559      * equal to zero.
1560      *
1561      * @param i the value whose number of trailing zeros is to be computed
1562      * @return the number of zero bits following the lowest-order ("rightmost")
1563      *     one-bit in the two's complement binary representation of the
1564      *     specified {@code int} value, or 32 if the value is equal
1565      *     to zero.
1566      * @since 1.5
1567      */
1568     public static int numberOfTrailingZeros(int i) {
1569         // HD, Figure 5-14
1570         int y;
1571         if (i == 0) return 32;
1572         int n = 31;
1573         y = i <<16; if (y != 0) { n = n -16; i = y; }
1574         y = i << 8; if (y != 0) { n = n - 8; i = y; }
1575         y = i << 4; if (y != 0) { n = n - 4; i = y; }
1576         y = i << 2; if (y != 0) { n = n - 2; i = y; }
1577         return n - ((i << 1) >>> 31);
1578     }
1579 
1580     /**
1581      * Returns the number of one-bits in the two's complement binary
1582      * representation of the specified {@code int} value.  This function is
1583      * sometimes referred to as the <i>population count</i>.
1584      *
1585      * @param i the value whose bits are to be counted
1586      * @return the number of one-bits in the two's complement binary
1587      *     representation of the specified {@code int} value.
1588      * @since 1.5
1589      */
1590     public static int bitCount(int i) {
1591         // HD, Figure 5-2
1592         i = i - ((i >>> 1) & 0x55555555);
1593         i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1594         i = (i + (i >>> 4)) & 0x0f0f0f0f;
1595         i = i + (i >>> 8);
1596         i = i + (i >>> 16);
1597         return i & 0x3f;
1598     }
1599 
1600     /**
1601      * Returns the value obtained by rotating the two's complement binary
1602      * representation of the specified {@code int} value left by the
1603      * specified number of bits.  (Bits shifted out of the left hand, or
1604      * high-order, side reenter on the right, or low-order.)
1605      *
1606      * <p>Note that left rotation with a negative distance is equivalent to
1607      * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1608      * distance)}.  Note also that rotation by any multiple of 32 is a
1609      * no-op, so all but the last five bits of the rotation distance can be
1610      * ignored, even if the distance is negative: {@code rotateLeft(val,
1611      * distance) == rotateLeft(val, distance & 0x1F)}.
1612      *
1613      * @param i the value whose bits are to be rotated left
1614      * @param distance the number of bit positions to rotate left
1615      * @return the value obtained by rotating the two's complement binary
1616      *     representation of the specified {@code int} value left by the
1617      *     specified number of bits.
1618      * @since 1.5
1619      */
1620     public static int rotateLeft(int i, int distance) {
1621         return (i << distance) | (i >>> -distance);
1622     }
1623 
1624     /**
1625      * Returns the value obtained by rotating the two's complement binary
1626      * representation of the specified {@code int} value right by the
1627      * specified number of bits.  (Bits shifted out of the right hand, or
1628      * low-order, side reenter on the left, or high-order.)
1629      *
1630      * <p>Note that right rotation with a negative distance is equivalent to
1631      * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1632      * distance)}.  Note also that rotation by any multiple of 32 is a
1633      * no-op, so all but the last five bits of the rotation distance can be
1634      * ignored, even if the distance is negative: {@code rotateRight(val,
1635      * distance) == rotateRight(val, distance & 0x1F)}.
1636      *
1637      * @param i the value whose bits are to be rotated right
1638      * @param distance the number of bit positions to rotate right
1639      * @return the value obtained by rotating the two's complement binary
1640      *     representation of the specified {@code int} value right by the
1641      *     specified number of bits.
1642      * @since 1.5
1643      */
1644     public static int rotateRight(int i, int distance) {
1645         return (i >>> distance) | (i << -distance);
1646     }
1647 
1648     /**
1649      * Returns the value obtained by reversing the order of the bits in the
1650      * two's complement binary representation of the specified {@code int}
1651      * value.
1652      *
1653      * @param i the value to be reversed
1654      * @return the value obtained by reversing order of the bits in the
1655      *     specified {@code int} value.
1656      * @since 1.5
1657      */
1658     public static int reverse(int i) {
1659         // HD, Figure 7-1
1660         i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1661         i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1662         i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1663         i = (i << 24) | ((i & 0xff00) << 8) |
1664             ((i >>> 8) & 0xff00) | (i >>> 24);
1665         return i;
1666     }
1667 
1668     /**
1669      * Returns the signum function of the specified {@code int} value.  (The
1670      * return value is -1 if the specified value is negative; 0 if the
1671      * specified value is zero; and 1 if the specified value is positive.)
1672      *
1673      * @param i the value whose signum is to be computed
1674      * @return the signum function of the specified {@code int} value.
1675      * @since 1.5
1676      */
1677     public static int signum(int i) {
1678         // HD, Section 2-7
1679         return (i >> 31) | (-i >>> 31);
1680     }
1681 
1682     /**
1683      * Returns the value obtained by reversing the order of the bytes in the
1684      * two's complement representation of the specified {@code int} value.
1685      *
1686      * @param i the value whose bytes are to be reversed
1687      * @return the value obtained by reversing the bytes in the specified
1688      *     {@code int} value.
1689      * @since 1.5
1690      */
1691     public static int reverseBytes(int i) {
1692         return ((i >>> 24)           ) |
1693                ((i >>   8) &   0xFF00) |
1694                ((i <<   8) & 0xFF0000) |
1695                ((i << 24));
1696     }
1697 
1698     /**
1699      * Adds two integers together as per the + operator.
1700      *
1701      * @param a the first operand
1702      * @param b the second operand
1703      * @return the sum of {@code a} and {@code b}
1704      * @see java.util.function.BinaryOperator
1705      * @since 1.8
1706      */
1707     public static int sum(int a, int b) {
1708         return a + b;
1709     }
1710 
1711     /**
1712      * Returns the greater of two {@code int} values
1713      * as if by calling {@link Math#max(int, int) Math.max}.
1714      *
1715      * @param a the first operand
1716      * @param b the second operand
1717      * @return the greater of {@code a} and {@code b}
1718      * @see java.util.function.BinaryOperator
1719      * @since 1.8
1720      */
1721     public static int max(int a, int b) {
1722         return Math.max(a, b);
1723     }
1724 
1725     /**
1726      * Returns the smaller of two {@code int} values
1727      * as if by calling {@link Math#min(int, int) Math.min}.
1728      *
1729      * @param a the first operand
1730      * @param b the second operand
1731      * @return the smaller of {@code a} and {@code b}
1732      * @see java.util.function.BinaryOperator
1733      * @since 1.8
1734      */
1735     public static int min(int a, int b) {
1736         return Math.min(a, b);
1737     }
1738 
1739     /** use serialVersionUID from JDK 1.0.2 for interoperability */
1740     @Native private static final long serialVersionUID = 1360826667806852920L;
1741 }