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 import jdk.internal.HotSpotIntrinsicCandidate;
  31 
  32 import static java.lang.String.COMPACT_STRINGS;
  33 import static java.lang.String.LATIN1;
  34 import static java.lang.String.UTF16;
  35 
  36 /**
  37  * The {@code Integer} class wraps a value of the primitive type
  38  * {@code int} in an object. An object of type {@code Integer}
  39  * contains a single field whose type is {@code int}.
  40  *
  41  * <p>In addition, this class provides several methods for converting
  42  * an {@code int} to a {@code String} and a {@code String} to an
  43  * {@code int}, as well as other constants and methods useful when
  44  * dealing with an {@code int}.
  45  *
  46  * <p>Implementation note: The implementations of the "bit twiddling"
  47  * methods (such as {@link #highestOneBit(int) highestOneBit} and
  48  * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
  49  * based on material from Henry S. Warren, Jr.'s <i>Hacker's
  50  * Delight</i>, (Addison Wesley, 2002).
  51  *
  52  * @author  Lee Boynton
  53  * @author  Arthur van Hoff
  54  * @author  Josh Bloch
  55  * @author  Joseph D. Darcy
  56  * @since 1.0
  57  */
  58 public final class Integer extends Number implements Comparable<Integer> {
  59     /**
  60      * A constant holding the minimum value an {@code int} can
  61      * have, -2<sup>31</sup>.
  62      */
  63     @Native public static final int   MIN_VALUE = 0x80000000;
  64 
  65     /**
  66      * A constant holding the maximum value an {@code int} can
  67      * have, 2<sup>31</sup>-1.
  68      */
  69     @Native public static final int   MAX_VALUE = 0x7fffffff;
  70 
  71     /**
  72      * The {@code Class} instance representing the primitive type
  73      * {@code int}.
  74      *
  75      * @since   1.1
  76      */
  77     @SuppressWarnings("unchecked")
  78     public static final Class<Integer>  TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
  79 
  80     /**
  81      * All possible chars for representing a number as a String
  82      */
  83     static final char[] digits = {
  84         '0' , '1' , '2' , '3' , '4' , '5' ,
  85         '6' , '7' , '8' , '9' , 'a' , 'b' ,
  86         'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
  87         'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
  88         'o' , 'p' , 'q' , 'r' , 's' , 't' ,
  89         'u' , 'v' , 'w' , 'x' , 'y' , 'z'
  90     };
  91 
  92     /**
  93      * Returns a string representation of the first argument in the
  94      * radix specified by the second argument.
  95      *
  96      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
  97      * or larger than {@code Character.MAX_RADIX}, then the radix
  98      * {@code 10} is used instead.
  99      *
 100      * <p>If the first argument is negative, the first element of the
 101      * result is the ASCII minus character {@code '-'}
 102      * ({@code '\u005Cu002D'}). If the first argument is not
 103      * negative, no sign character appears in the result.
 104      *
 105      * <p>The remaining characters of the result represent the magnitude
 106      * of the first argument. If the magnitude is zero, it is
 107      * represented by a single zero character {@code '0'}
 108      * ({@code '\u005Cu0030'}); otherwise, the first character of
 109      * the representation of the magnitude will not be the zero
 110      * character.  The following ASCII characters are used as digits:
 111      *
 112      * <blockquote>
 113      *   {@code 0123456789abcdefghijklmnopqrstuvwxyz}
 114      * </blockquote>
 115      *
 116      * These are {@code '\u005Cu0030'} through
 117      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 118      * {@code '\u005Cu007A'}. If {@code radix} is
 119      * <var>N</var>, then the first <var>N</var> of these characters
 120      * are used as radix-<var>N</var> digits in the order shown. Thus,
 121      * the digits for hexadecimal (radix 16) are
 122      * {@code 0123456789abcdef}. If uppercase letters are
 123      * desired, the {@link java.lang.String#toUpperCase()} method may
 124      * be called on the result:
 125      *
 126      * <blockquote>
 127      *  {@code Integer.toString(n, 16).toUpperCase()}
 128      * </blockquote>
 129      *
 130      * @param   i       an integer to be converted to a string.
 131      * @param   radix   the radix to use in the string representation.
 132      * @return  a string representation of the argument in the specified radix.
 133      * @see     java.lang.Character#MAX_RADIX
 134      * @see     java.lang.Character#MIN_RADIX
 135      */
 136     public static String toString(int i, int radix) {
 137         if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
 138             radix = 10;
 139 
 140         /* Use the faster version */
 141         if (radix == 10) {
 142             return toString(i);
 143         }
 144 
 145         if (COMPACT_STRINGS) {
 146             byte[] buf = new byte[33];
 147             boolean negative = (i < 0);
 148             int charPos = 32;
 149 
 150             if (!negative) {
 151                 i = -i;
 152             }
 153 
 154             while (i <= -radix) {
 155                 buf[charPos--] = (byte)digits[-(i % radix)];
 156                 i = i / radix;
 157             }
 158             buf[charPos] = (byte)digits[-i];
 159 
 160             if (negative) {
 161                 buf[--charPos] = '-';
 162             }
 163 
 164             return StringLatin1.newString(buf, charPos, (33 - charPos));
 165         }
 166         return toStringUTF16(i, radix);
 167     }
 168 
 169     private static String toStringUTF16(int i, int radix) {
 170         byte[] buf = new byte[33 * 2];
 171         boolean negative = (i < 0);
 172         int charPos = 32;
 173         if (!negative) {
 174             i = -i;
 175         }
 176         while (i <= -radix) {
 177             StringUTF16.putChar(buf, charPos--, digits[-(i % radix)]);
 178             i = i / radix;
 179         }
 180         StringUTF16.putChar(buf, charPos, digits[-i]);
 181 
 182         if (negative) {
 183             StringUTF16.putChar(buf, --charPos, '-');
 184         }
 185         return StringUTF16.newString(buf, charPos, (33 - charPos));
 186     }
 187 
 188     /**
 189      * Returns a string representation of the first argument as an
 190      * unsigned integer value in the radix specified by the second
 191      * argument.
 192      *
 193      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
 194      * or larger than {@code Character.MAX_RADIX}, then the radix
 195      * {@code 10} is used instead.
 196      *
 197      * <p>Note that since the first argument is treated as an unsigned
 198      * value, no leading sign character is printed.
 199      *
 200      * <p>If the magnitude is zero, it is represented by a single zero
 201      * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
 202      * the first character of the representation of the magnitude will
 203      * not be the zero character.
 204      *
 205      * <p>The behavior of radixes and the characters used as digits
 206      * are the same as {@link #toString(int, int) toString}.
 207      *
 208      * @param   i       an integer to be converted to an unsigned string.
 209      * @param   radix   the radix to use in the string representation.
 210      * @return  an unsigned string representation of the argument in the specified radix.
 211      * @see     #toString(int, int)
 212      * @since 1.8
 213      */
 214     public static String toUnsignedString(int i, int radix) {
 215         return Long.toUnsignedString(toUnsignedLong(i), radix);
 216     }
 217 
 218     /**
 219      * Returns a string representation of the integer argument as an
 220      * unsigned integer in base&nbsp;16.
 221      *
 222      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 223      * if the argument is negative; otherwise, it is equal to the
 224      * argument.  This value is converted to a string of ASCII digits
 225      * in hexadecimal (base&nbsp;16) with no extra leading
 226      * {@code 0}s.
 227      *
 228      * <p>The value of the argument can be recovered from the returned
 229      * string {@code s} by calling {@link
 230      * Integer#parseUnsignedInt(String, int)
 231      * Integer.parseUnsignedInt(s, 16)}.
 232      *
 233      * <p>If the unsigned magnitude is zero, it is represented by a
 234      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 235      * otherwise, the first character of the representation of the
 236      * unsigned magnitude will not be the zero character. The
 237      * following characters are used as hexadecimal digits:
 238      *
 239      * <blockquote>
 240      *  {@code 0123456789abcdef}
 241      * </blockquote>
 242      *
 243      * These are the characters {@code '\u005Cu0030'} through
 244      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 245      * {@code '\u005Cu0066'}. If uppercase letters are
 246      * desired, the {@link java.lang.String#toUpperCase()} method may
 247      * be called on the result:
 248      *
 249      * <blockquote>
 250      *  {@code Integer.toHexString(n).toUpperCase()}
 251      * </blockquote>
 252      *
 253      * @param   i   an integer to be converted to a string.
 254      * @return  the string representation of the unsigned integer value
 255      *          represented by the argument in hexadecimal (base&nbsp;16).
 256      * @see #parseUnsignedInt(String, int)
 257      * @see #toUnsignedString(int, int)
 258      * @since   1.0.2
 259      */
 260     public static String toHexString(int i) {
 261         return toUnsignedString0(i, 4);
 262     }
 263 
 264     /**
 265      * Returns a string representation of the integer argument as an
 266      * unsigned integer in base&nbsp;8.
 267      *
 268      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 269      * if the argument is negative; otherwise, it is equal to the
 270      * argument.  This value is converted to a string of ASCII digits
 271      * in octal (base&nbsp;8) with no extra leading {@code 0}s.
 272      *
 273      * <p>The value of the argument can be recovered from the returned
 274      * string {@code s} by calling {@link
 275      * Integer#parseUnsignedInt(String, int)
 276      * Integer.parseUnsignedInt(s, 8)}.
 277      *
 278      * <p>If the unsigned magnitude is zero, it is represented by a
 279      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 280      * otherwise, the first character of the representation of the
 281      * unsigned magnitude will not be the zero character. The
 282      * following characters are used as octal digits:
 283      *
 284      * <blockquote>
 285      * {@code 01234567}
 286      * </blockquote>
 287      *
 288      * These are the characters {@code '\u005Cu0030'} through
 289      * {@code '\u005Cu0037'}.
 290      *
 291      * @param   i   an integer to be converted to a string.
 292      * @return  the string representation of the unsigned integer value
 293      *          represented by the argument in octal (base&nbsp;8).
 294      * @see #parseUnsignedInt(String, int)
 295      * @see #toUnsignedString(int, int)
 296      * @since   1.0.2
 297      */
 298     public static String toOctalString(int i) {
 299         return toUnsignedString0(i, 3);
 300     }
 301 
 302     /**
 303      * Returns a string representation of the integer argument as an
 304      * unsigned integer in base&nbsp;2.
 305      *
 306      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 307      * if the argument is negative; otherwise it is equal to the
 308      * argument.  This value is converted to a string of ASCII digits
 309      * in binary (base&nbsp;2) with no extra leading {@code 0}s.
 310      *
 311      * <p>The value of the argument can be recovered from the returned
 312      * string {@code s} by calling {@link
 313      * Integer#parseUnsignedInt(String, int)
 314      * Integer.parseUnsignedInt(s, 2)}.
 315      *
 316      * <p>If the unsigned magnitude is zero, it is represented by a
 317      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 318      * otherwise, the first character of the representation of the
 319      * unsigned magnitude will not be the zero character. The
 320      * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
 321      * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
 322      *
 323      * @param   i   an integer to be converted to a string.
 324      * @return  the string representation of the unsigned integer value
 325      *          represented by the argument in binary (base&nbsp;2).
 326      * @see #parseUnsignedInt(String, int)
 327      * @see #toUnsignedString(int, int)
 328      * @since   1.0.2
 329      */
 330     public static String toBinaryString(int i) {
 331         return toUnsignedString0(i, 1);
 332     }
 333 
 334     /**
 335      * Convert the integer to an unsigned number.
 336      */
 337     private static String toUnsignedString0(int val, int shift) {
 338         // assert shift > 0 && shift <=5 : "Illegal shift value";
 339         int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
 340         int chars = Math.max(((mag + (shift - 1)) / shift), 1);
 341 
 342         if (COMPACT_STRINGS) {
 343             byte[] buf = new byte[chars];
 344             formatUnsignedInt(val, shift, buf, 0, chars);
 345             return new String(buf, LATIN1);
 346         } else {
 347             byte[] buf = new byte[chars * 2];
 348             formatUnsignedIntUTF16(val, shift, buf, 0, chars);
 349             return new String(buf, UTF16);
 350         }
 351     }
 352 
 353     /**
 354      * Format an {@code int} (treated as unsigned) into a character buffer. If
 355      * {@code len} exceeds the formatted ASCII representation of {@code val},
 356      * {@code buf} will be padded with leading zeroes.
 357      *
 358      * @param val the unsigned int to format
 359      * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
 360      * @param buf the character buffer to write to
 361      * @param offset the offset in the destination buffer to start at
 362      * @param len the number of characters to write
 363      */
 364     static void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
 365         // assert shift > 0 && shift <=5 : "Illegal shift value";
 366         // assert offset >= 0 && offset < buf.length : "illegal offset";
 367         // assert len > 0 && (offset + len) <= buf.length : "illegal length";
 368         int charPos = offset + len;
 369         int radix = 1 << shift;
 370         int mask = radix - 1;
 371         do {
 372             buf[--charPos] = Integer.digits[val & mask];
 373             val >>>= shift;
 374         } while (charPos > offset);
 375     }
 376 
 377     /** byte[]/LATIN1 version    */
 378     static void formatUnsignedInt(int val, int shift, byte[] buf, int offset, int len) {
 379         int charPos = offset + len;
 380         int radix = 1 << shift;
 381         int mask = radix - 1;
 382         do {
 383             buf[--charPos] = (byte)Integer.digits[val & mask];
 384             val >>>= shift;
 385         } while (charPos > offset);
 386     }
 387 
 388     /** byte[]/UTF16 version    */
 389     static void formatUnsignedIntUTF16(int val, int shift, byte[] buf, int offset, int len) {
 390         int charPos = offset + len;
 391         int radix = 1 << shift;
 392         int mask = radix - 1;
 393         do {
 394             StringUTF16.putChar(buf, --charPos, Integer.digits[val & mask]);
 395             val >>>= shift;
 396         } while (charPos > offset);
 397     }
 398 
 399     static final char [] DigitTens = {
 400         '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
 401         '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
 402         '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
 403         '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
 404         '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
 405         '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
 406         '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
 407         '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
 408         '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
 409         '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
 410         } ;
 411 
 412     static final char [] DigitOnes = {
 413         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 414         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 415         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 416         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 417         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 418         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 419         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 420         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 421         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 422         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 423         } ;
 424 
 425         // I use the "invariant division by multiplication" trick to
 426         // accelerate Integer.toString.  In particular we want to
 427         // avoid division by 10.
 428         //
 429         // The "trick" has roughly the same performance characteristics
 430         // as the "classic" Integer.toString code on a non-JIT VM.
 431         // The trick avoids .rem and .div calls but has a longer code
 432         // path and is thus dominated by dispatch overhead.  In the
 433         // JIT case the dispatch overhead doesn't exist and the
 434         // "trick" is considerably faster than the classic code.
 435         //
 436         // RE:  Division by Invariant Integers using Multiplication
 437         //      T Gralund, P Montgomery
 438         //      ACM PLDI 1994
 439         //
 440 
 441     /**
 442      * Returns a {@code String} object representing the
 443      * specified integer. The argument is converted to signed decimal
 444      * representation and returned as a string, exactly as if the
 445      * argument and radix 10 were given as arguments to the {@link
 446      * #toString(int, int)} method.
 447      *
 448      * @param   i   an integer to be converted.
 449      * @return  a string representation of the argument in base&nbsp;10.
 450      */
 451     @HotSpotIntrinsicCandidate
 452     public static String toString(int i) {
 453         if (i == Integer.MIN_VALUE)
 454             return "-2147483648";
 455         int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
 456         if (COMPACT_STRINGS) {
 457             byte[] buf = new byte[size];
 458             getChars(i, size, buf);
 459             return new String(buf, LATIN1);
 460         } else {
 461             byte[] buf = new byte[size * 2];
 462             getCharsUTF16(i, size, buf);
 463             return new String(buf, UTF16);
 464         }
 465     }
 466 
 467     /**
 468      * Returns a string representation of the argument as an unsigned
 469      * decimal value.
 470      *
 471      * The argument is converted to unsigned decimal representation
 472      * and returned as a string exactly as if the argument and radix
 473      * 10 were given as arguments to the {@link #toUnsignedString(int,
 474      * int)} method.
 475      *
 476      * @param   i  an integer to be converted to an unsigned string.
 477      * @return  an unsigned string representation of the argument.
 478      * @see     #toUnsignedString(int, int)
 479      * @since 1.8
 480      */
 481     public static String toUnsignedString(int i) {
 482         return Long.toString(toUnsignedLong(i));
 483     }
 484 
 485     /**
 486      * Places characters representing the integer i into the
 487      * character array buf. The characters are placed into
 488      * the buffer backwards starting with the least significant
 489      * digit at the specified index (exclusive), and working
 490      * backwards from there.
 491      *
 492      * Will fail if i == Integer.MIN_VALUE
 493      */
 494     static void getChars(int i, int index, byte[] buf) {
 495         int q, r;
 496         int charPos = index;
 497         char sign = 0;
 498 
 499         if (i < 0) {
 500             sign = '-';
 501             i = -i;
 502         }
 503 
 504         // Generate two digits per iteration
 505         while (i >= 65536) {
 506             q = i / 100;
 507         // really: r = i - (q * 100);
 508             r = i - ((q << 6) + (q << 5) + (q << 2));
 509             i = q;
 510             buf [--charPos] = (byte)DigitOnes[r];
 511             buf [--charPos] = (byte)DigitTens[r];
 512         }
 513 
 514         // Fall thru to fast mode for smaller numbers
 515         // assert(i <= 65536, i);
 516         for (;;) {
 517             q = (i * 52429) >>> (16+3);
 518             r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...
 519             buf [--charPos] = (byte)digits [r];
 520             i = q;
 521             if (i == 0) break;
 522         }
 523         if (sign != 0) {
 524             buf [--charPos] = (byte)sign;
 525         }
 526     }
 527 
 528     static void getCharsUTF16(int i, int index, byte[] buf) {
 529         int q, r;
 530         int charPos = index;
 531         char sign = 0;
 532 
 533         if (i < 0) {
 534             sign = '-';
 535             i = -i;
 536         }
 537 
 538         // Generate two digits per iteration
 539         while (i >= 65536) {
 540             q = i / 100;
 541         // really: r = i - (q * 100);
 542             r = i - ((q << 6) + (q << 5) + (q << 2));
 543             i = q;
 544             StringUTF16.putChar(buf, --charPos, DigitOnes[r]);
 545             StringUTF16.putChar(buf, --charPos, DigitTens[r]);
 546         }
 547 
 548         // Fall thru to fast mode for smaller numbers
 549         // assert(i <= 65536, i);
 550         for (;;) {
 551             q = (i * 52429) >>> (16+3);
 552             r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...
 553             StringUTF16.putChar(buf, --charPos, Integer.digits[r]);
 554             i = q;
 555             if (i == 0) break;
 556         }
 557         if (sign != 0) {
 558             StringUTF16.putChar(buf, --charPos, sign);
 559         }
 560     }
 561 
 562     static final int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
 563                                       99999999, 999999999, Integer.MAX_VALUE };
 564 
 565     // Requires positive x
 566     static int stringSize(int x) {
 567         for (int i=0; ; i++)
 568             if (x <= sizeTable[i])
 569                 return i+1;
 570     }
 571 
 572     /**
 573      * Parses the string argument as a signed integer in the radix
 574      * specified by the second argument. The characters in the string
 575      * must all be digits of the specified radix (as determined by
 576      * whether {@link java.lang.Character#digit(char, int)} returns a
 577      * nonnegative value), except that the first character may be an
 578      * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
 579      * indicate a negative value or an ASCII plus sign {@code '+'}
 580      * ({@code '\u005Cu002B'}) to indicate a positive value. The
 581      * resulting integer value is returned.
 582      *
 583      * <p>An exception of type {@code NumberFormatException} is
 584      * thrown if any of the following situations occurs:
 585      * <ul>
 586      * <li>The first argument is {@code null} or is a string of
 587      * length zero.
 588      *
 589      * <li>The radix is either smaller than
 590      * {@link java.lang.Character#MIN_RADIX} or
 591      * larger than {@link java.lang.Character#MAX_RADIX}.
 592      *
 593      * <li>Any character of the string is not a digit of the specified
 594      * radix, except that the first character may be a minus sign
 595      * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
 596      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 597      * string is longer than length 1.
 598      *
 599      * <li>The value represented by the string is not a value of type
 600      * {@code int}.
 601      * </ul>
 602      *
 603      * <p>Examples:
 604      * <blockquote><pre>
 605      * parseInt("0", 10) returns 0
 606      * parseInt("473", 10) returns 473
 607      * parseInt("+42", 10) returns 42
 608      * parseInt("-0", 10) returns 0
 609      * parseInt("-FF", 16) returns -255
 610      * parseInt("1100110", 2) returns 102
 611      * parseInt("2147483647", 10) returns 2147483647
 612      * parseInt("-2147483648", 10) returns -2147483648
 613      * parseInt("2147483648", 10) throws a NumberFormatException
 614      * parseInt("99", 8) throws a NumberFormatException
 615      * parseInt("Kona", 10) throws a NumberFormatException
 616      * parseInt("Kona", 27) returns 411787
 617      * </pre></blockquote>
 618      *
 619      * @param      s   the {@code String} containing the integer
 620      *                  representation to be parsed
 621      * @param      radix   the radix to be used while parsing {@code s}.
 622      * @return     the integer represented by the string argument in the
 623      *             specified radix.
 624      * @exception  NumberFormatException if the {@code String}
 625      *             does not contain a parsable {@code int}.
 626      */
 627     public static int parseInt(String s, int radix)
 628                 throws NumberFormatException
 629     {
 630         /*
 631          * WARNING: This method may be invoked early during VM initialization
 632          * before IntegerCache is initialized. Care must be taken to not use
 633          * the valueOf method.
 634          */
 635 
 636         if (s == null) {
 637             throw new NumberFormatException("null");
 638         }
 639 
 640         if (radix < Character.MIN_RADIX) {
 641             throw new NumberFormatException("radix " + radix +
 642                                             " less than Character.MIN_RADIX");
 643         }
 644 
 645         if (radix > Character.MAX_RADIX) {
 646             throw new NumberFormatException("radix " + radix +
 647                                             " greater than Character.MAX_RADIX");
 648         }
 649 
 650         boolean negative = false;
 651         int i = 0, len = s.length();
 652         int limit = -Integer.MAX_VALUE;
 653 
 654         if (len > 0) {
 655             char firstChar = s.charAt(0);
 656             if (firstChar < '0') { // Possible leading "+" or "-"
 657                 if (firstChar == '-') {
 658                     negative = true;
 659                     limit = Integer.MIN_VALUE;
 660                 } else if (firstChar != '+') {
 661                     throw NumberFormatException.forInputString(s);
 662                 }
 663 
 664                 if (len == 1) { // Cannot have lone "+" or "-"
 665                     throw NumberFormatException.forInputString(s);
 666                 }
 667                 i++;
 668             }
 669             int multmin = limit / radix;
 670             int result = 0;
 671             while (i < len) {
 672                 // Accumulating negatively avoids surprises near MAX_VALUE
 673                 int digit = Character.digit(s.charAt(i++), radix);
 674                 if (digit < 0 || result < multmin) {
 675                     throw NumberFormatException.forInputString(s);
 676                 }
 677                 result *= radix;
 678                 if (result < limit + digit) {
 679                     throw NumberFormatException.forInputString(s);
 680                 }
 681                 result -= digit;
 682             }
 683             return negative ? result : -result;
 684         } else {
 685             throw NumberFormatException.forInputString(s);
 686         }
 687     }
 688 
 689     /**
 690      * Parses the {@link CharSequence} argument as a signed {@code int} in the
 691      * specified {@code radix}, beginning at the specified {@code beginIndex}
 692      * and extending to {@code endIndex - 1}.
 693      *
 694      * <p>The method does not take steps to guard against the
 695      * {@code CharSequence} being mutated while parsing.
 696      *
 697      * @param      s   the {@code CharSequence} containing the {@code int}
 698      *                  representation to be parsed
 699      * @param      beginIndex   the beginning index, inclusive.
 700      * @param      endIndex     the ending index, exclusive.
 701      * @param      radix   the radix to be used while parsing {@code s}.
 702      * @return     the signed {@code int} represented by the subsequence in
 703      *             the specified radix.
 704      * @throws     NullPointerException  if {@code s} is null.
 705      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 706      *             negative, or if {@code beginIndex} is greater than
 707      *             {@code endIndex} or if {@code endIndex} is greater than
 708      *             {@code s.length()}.
 709      * @throws     NumberFormatException  if the {@code CharSequence} does not
 710      *             contain a parsable {@code int} in the specified
 711      *             {@code radix}, or if {@code radix} is either smaller than
 712      *             {@link java.lang.Character#MIN_RADIX} or larger than
 713      *             {@link java.lang.Character#MAX_RADIX}.
 714      * @since  1.9
 715      */
 716     public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix)
 717                 throws NumberFormatException {
 718         s = Objects.requireNonNull(s);
 719 
 720         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 721             throw new IndexOutOfBoundsException();
 722         }
 723         if (radix < Character.MIN_RADIX) {
 724             throw new NumberFormatException("radix " + radix +
 725                                             " less than Character.MIN_RADIX");
 726         }
 727         if (radix > Character.MAX_RADIX) {
 728             throw new NumberFormatException("radix " + radix +
 729                                             " greater than Character.MAX_RADIX");
 730         }
 731 
 732         boolean negative = false;
 733         int i = beginIndex;
 734         int limit = -Integer.MAX_VALUE;
 735 
 736         if (i < endIndex) {
 737             char firstChar = s.charAt(i);
 738             if (firstChar < '0') { // Possible leading "+" or "-"
 739                 if (firstChar == '-') {
 740                     negative = true;
 741                     limit = Integer.MIN_VALUE;
 742                 } else if (firstChar != '+') {
 743                     throw NumberFormatException.forCharSequence(s, beginIndex,
 744                             endIndex, i);
 745                 }
 746                 i++;
 747                 if (i == endIndex) { // Cannot have lone "+" or "-"
 748                     throw NumberFormatException.forCharSequence(s, beginIndex,
 749                             endIndex, i);
 750                 }
 751             }
 752             int multmin = limit / radix;
 753             int result = 0;
 754             while (i < endIndex) {
 755                 // Accumulating negatively avoids surprises near MAX_VALUE
 756                 int digit = Character.digit(s.charAt(i), radix);
 757                 if (digit < 0 || result < multmin) {
 758                     throw NumberFormatException.forCharSequence(s, beginIndex,
 759                             endIndex, i);
 760                 }
 761                 result *= radix;
 762                 if (result < limit + digit) {
 763                     throw NumberFormatException.forCharSequence(s, beginIndex,
 764                             endIndex, i);
 765                 }
 766                 i++;
 767                 result -= digit;
 768             }
 769             return negative ? result : -result;
 770         } else {
 771             throw NumberFormatException.forInputString("");
 772         }
 773     }
 774 
 775     /**
 776      * Parses the string argument as a signed decimal integer. The
 777      * characters in the string must all be decimal digits, except
 778      * that the first character may be an ASCII minus sign {@code '-'}
 779      * ({@code '\u005Cu002D'}) to indicate a negative value or an
 780      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
 781      * indicate a positive value. The resulting integer value is
 782      * returned, exactly as if the argument and the radix 10 were
 783      * given as arguments to the {@link #parseInt(java.lang.String,
 784      * int)} method.
 785      *
 786      * @param s    a {@code String} containing the {@code int}
 787      *             representation to be parsed
 788      * @return     the integer value represented by the argument in decimal.
 789      * @exception  NumberFormatException  if the string does not contain a
 790      *               parsable integer.
 791      */
 792     public static int parseInt(String s) throws NumberFormatException {
 793         return parseInt(s,10);
 794     }
 795 
 796     /**
 797      * Parses the string argument as an unsigned integer in the radix
 798      * specified by the second argument.  An unsigned integer maps the
 799      * values usually associated with negative numbers to positive
 800      * numbers larger than {@code MAX_VALUE}.
 801      *
 802      * The characters in the string must all be digits of the
 803      * specified radix (as determined by whether {@link
 804      * java.lang.Character#digit(char, int)} returns a nonnegative
 805      * value), except that the first character may be an ASCII plus
 806      * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
 807      * integer value is returned.
 808      *
 809      * <p>An exception of type {@code NumberFormatException} is
 810      * thrown if any of the following situations occurs:
 811      * <ul>
 812      * <li>The first argument is {@code null} or is a string of
 813      * length zero.
 814      *
 815      * <li>The radix is either smaller than
 816      * {@link java.lang.Character#MIN_RADIX} or
 817      * larger than {@link java.lang.Character#MAX_RADIX}.
 818      *
 819      * <li>Any character of the string is not a digit of the specified
 820      * radix, except that the first character may be a plus sign
 821      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 822      * string is longer than length 1.
 823      *
 824      * <li>The value represented by the string is larger than the
 825      * largest unsigned {@code int}, 2<sup>32</sup>-1.
 826      *
 827      * </ul>
 828      *
 829      *
 830      * @param      s   the {@code String} containing the unsigned integer
 831      *                  representation to be parsed
 832      * @param      radix   the radix to be used while parsing {@code s}.
 833      * @return     the integer represented by the string argument in the
 834      *             specified radix.
 835      * @throws     NumberFormatException if the {@code String}
 836      *             does not contain a parsable {@code int}.
 837      * @since 1.8
 838      */
 839     public static int parseUnsignedInt(String s, int radix)
 840                 throws NumberFormatException {
 841         if (s == null)  {
 842             throw new NumberFormatException("null");
 843         }
 844 
 845         int len = s.length();
 846         if (len > 0) {
 847             char firstChar = s.charAt(0);
 848             if (firstChar == '-') {
 849                 throw new
 850                     NumberFormatException(String.format("Illegal leading minus sign " +
 851                                                        "on unsigned string %s.", s));
 852             } else {
 853                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 854                     (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
 855                     return parseInt(s, radix);
 856                 } else {
 857                     long ell = Long.parseLong(s, radix);
 858                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 859                         return (int) ell;
 860                     } else {
 861                         throw new
 862                             NumberFormatException(String.format("String value %s exceeds " +
 863                                                                 "range of unsigned int.", s));
 864                     }
 865                 }
 866             }
 867         } else {
 868             throw NumberFormatException.forInputString(s);
 869         }
 870     }
 871 
 872     /**
 873      * Parses the {@link CharSequence} argument as an unsigned {@code int} in
 874      * the specified {@code radix}, beginning at the specified
 875      * {@code beginIndex} and extending to {@code endIndex - 1}.
 876      *
 877      * <p>The method does not take steps to guard against the
 878      * {@code CharSequence} being mutated while parsing.
 879      *
 880      * @param      s   the {@code CharSequence} containing the unsigned
 881      *                 {@code int} representation to be parsed
 882      * @param      beginIndex   the beginning index, inclusive.
 883      * @param      endIndex     the ending index, exclusive.
 884      * @param      radix   the radix to be used while parsing {@code s}.
 885      * @return     the unsigned {@code int} represented by the subsequence in
 886      *             the specified radix.
 887      * @throws     NullPointerException  if {@code s} is null.
 888      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 889      *             negative, or if {@code beginIndex} is greater than
 890      *             {@code endIndex} or if {@code endIndex} is greater than
 891      *             {@code s.length()}.
 892      * @throws     NumberFormatException  if the {@code CharSequence} does not
 893      *             contain a parsable unsigned {@code int} in the specified
 894      *             {@code radix}, or if {@code radix} is either smaller than
 895      *             {@link java.lang.Character#MIN_RADIX} or larger than
 896      *             {@link java.lang.Character#MAX_RADIX}.
 897      * @since  1.9
 898      */
 899     public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix)
 900                 throws NumberFormatException {
 901         s = Objects.requireNonNull(s);
 902 
 903         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 904             throw new IndexOutOfBoundsException();
 905         }
 906         int start = beginIndex, len = endIndex - beginIndex;
 907 
 908         if (len > 0) {
 909             char firstChar = s.charAt(start);
 910             if (firstChar == '-') {
 911                 throw new
 912                     NumberFormatException(String.format("Illegal leading minus sign " +
 913                                                        "on unsigned string %s.", s));
 914             } else {
 915                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 916                         (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits
 917                     return parseInt(s, start, start + len, radix);
 918                 } else {
 919                     long ell = Long.parseLong(s, start, start + len, radix);
 920                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 921                         return (int) ell;
 922                     } else {
 923                         throw new
 924                             NumberFormatException(String.format("String value %s exceeds " +
 925                                                                 "range of unsigned int.", s));
 926                     }
 927                 }
 928             }
 929         } else {
 930             throw new NumberFormatException("");
 931         }
 932     }
 933 
 934     /**
 935      * Parses the string argument as an unsigned decimal integer. The
 936      * characters in the string must all be decimal digits, except
 937      * that the first character may be an ASCII plus sign {@code
 938      * '+'} ({@code '\u005Cu002B'}). The resulting integer value
 939      * is returned, exactly as if the argument and the radix 10 were
 940      * given as arguments to the {@link
 941      * #parseUnsignedInt(java.lang.String, int)} method.
 942      *
 943      * @param s   a {@code String} containing the unsigned {@code int}
 944      *            representation to be parsed
 945      * @return    the unsigned integer value represented by the argument in decimal.
 946      * @throws    NumberFormatException  if the string does not contain a
 947      *            parsable unsigned integer.
 948      * @since 1.8
 949      */
 950     public static int parseUnsignedInt(String s) throws NumberFormatException {
 951         return parseUnsignedInt(s, 10);
 952     }
 953 
 954     /**
 955      * Returns an {@code Integer} object holding the value
 956      * extracted from the specified {@code String} when parsed
 957      * with the radix given by the second argument. The first argument
 958      * is interpreted as representing a signed integer in the radix
 959      * specified by the second argument, exactly as if the arguments
 960      * were given to the {@link #parseInt(java.lang.String, int)}
 961      * method. The result is an {@code Integer} object that
 962      * represents the integer value specified by the string.
 963      *
 964      * <p>In other words, this method returns an {@code Integer}
 965      * object equal to the value of:
 966      *
 967      * <blockquote>
 968      *  {@code new Integer(Integer.parseInt(s, radix))}
 969      * </blockquote>
 970      *
 971      * @param      s   the string to be parsed.
 972      * @param      radix the radix to be used in interpreting {@code s}
 973      * @return     an {@code Integer} object holding the value
 974      *             represented by the string argument in the specified
 975      *             radix.
 976      * @exception NumberFormatException if the {@code String}
 977      *            does not contain a parsable {@code int}.
 978      */
 979     public static Integer valueOf(String s, int radix) throws NumberFormatException {
 980         return Integer.valueOf(parseInt(s,radix));
 981     }
 982 
 983     /**
 984      * Returns an {@code Integer} object holding the
 985      * value of the specified {@code String}. The argument is
 986      * interpreted as representing a signed decimal integer, exactly
 987      * as if the argument were given to the {@link
 988      * #parseInt(java.lang.String)} method. The result is an
 989      * {@code Integer} object that represents the integer value
 990      * specified by the string.
 991      *
 992      * <p>In other words, this method returns an {@code Integer}
 993      * object equal to the value of:
 994      *
 995      * <blockquote>
 996      *  {@code new Integer(Integer.parseInt(s))}
 997      * </blockquote>
 998      *
 999      * @param      s   the string to be parsed.
1000      * @return     an {@code Integer} object holding the value
1001      *             represented by the string argument.
1002      * @exception  NumberFormatException  if the string cannot be parsed
1003      *             as an integer.
1004      */
1005     public static Integer valueOf(String s) throws NumberFormatException {
1006         return Integer.valueOf(parseInt(s, 10));
1007     }
1008 
1009     /**
1010      * Cache to support the object identity semantics of autoboxing for values between
1011      * -128 and 127 (inclusive) as required by JLS.
1012      *
1013      * The cache is initialized on first usage.  The size of the cache
1014      * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
1015      * During VM initialization, java.lang.Integer.IntegerCache.high property
1016      * may be set and saved in the private system properties in the
1017      * sun.misc.VM class.
1018      */
1019 
1020     private static class IntegerCache {
1021         static final int low = -128;
1022         static final int high;
1023         static final Integer cache[];
1024 
1025         static {
1026             // high value may be configured by property
1027             int h = 127;
1028             String integerCacheHighPropValue =
1029                 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
1030             if (integerCacheHighPropValue != null) {
1031                 try {
1032                     int i = parseInt(integerCacheHighPropValue);
1033                     i = Math.max(i, 127);
1034                     // Maximum array size is Integer.MAX_VALUE
1035                     h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
1036                 } catch( NumberFormatException nfe) {
1037                     // If the property cannot be parsed into an int, ignore it.
1038                 }
1039             }
1040             high = h;
1041 
1042             cache = new Integer[(high - low) + 1];
1043             int j = low;
1044             for(int k = 0; k < cache.length; k++)
1045                 cache[k] = new Integer(j++);
1046 
1047             // range [-128, 127] must be interned (JLS7 5.1.7)
1048             assert IntegerCache.high >= 127;
1049         }
1050 
1051         private IntegerCache() {}
1052     }
1053 
1054     /**
1055      * Returns an {@code Integer} instance representing the specified
1056      * {@code int} value.  If a new {@code Integer} instance is not
1057      * required, this method should generally be used in preference to
1058      * the constructor {@link #Integer(int)}, as this method is likely
1059      * to yield significantly better space and time performance by
1060      * caching frequently requested values.
1061      *
1062      * This method will always cache values in the range -128 to 127,
1063      * inclusive, and may cache other values outside of this range.
1064      *
1065      * @param  i an {@code int} value.
1066      * @return an {@code Integer} instance representing {@code i}.
1067      * @since  1.5
1068      */
1069     @HotSpotIntrinsicCandidate
1070     public static Integer valueOf(int i) {
1071         if (i >= IntegerCache.low && i <= IntegerCache.high)
1072             return IntegerCache.cache[i + (-IntegerCache.low)];
1073         return new Integer(i);
1074     }
1075 
1076     /**
1077      * The value of the {@code Integer}.
1078      *
1079      * @serial
1080      */
1081     private final int value;
1082 
1083     /**
1084      * Constructs a newly allocated {@code Integer} object that
1085      * represents the specified {@code int} value.
1086      *
1087      * @param   value   the value to be represented by the
1088      *                  {@code Integer} object.
1089      */
1090     public Integer(int value) {
1091         this.value = value;
1092     }
1093 
1094     /**
1095      * Constructs a newly allocated {@code Integer} object that
1096      * represents the {@code int} value indicated by the
1097      * {@code String} parameter. The string is converted to an
1098      * {@code int} value in exactly the manner used by the
1099      * {@code parseInt} method for radix 10.
1100      *
1101      * @param      s   the {@code String} to be converted to an
1102      *                 {@code Integer}.
1103      * @exception  NumberFormatException  if the {@code String} does not
1104      *               contain a parsable integer.
1105      * @see        java.lang.Integer#parseInt(java.lang.String, int)
1106      */
1107     public Integer(String s) throws NumberFormatException {
1108         this.value = parseInt(s, 10);
1109     }
1110 
1111     /**
1112      * Returns the value of this {@code Integer} as a {@code byte}
1113      * after a narrowing primitive conversion.
1114      * @jls 5.1.3 Narrowing Primitive Conversions
1115      */
1116     public byte byteValue() {
1117         return (byte)value;
1118     }
1119 
1120     /**
1121      * Returns the value of this {@code Integer} as a {@code short}
1122      * after a narrowing primitive conversion.
1123      * @jls 5.1.3 Narrowing Primitive Conversions
1124      */
1125     public short shortValue() {
1126         return (short)value;
1127     }
1128 
1129     /**
1130      * Returns the value of this {@code Integer} as an
1131      * {@code int}.
1132      */
1133     @HotSpotIntrinsicCandidate
1134     public int intValue() {
1135         return value;
1136     }
1137 
1138     /**
1139      * Returns the value of this {@code Integer} as a {@code long}
1140      * after a widening primitive conversion.
1141      * @jls 5.1.2 Widening Primitive Conversions
1142      * @see Integer#toUnsignedLong(int)
1143      */
1144     public long longValue() {
1145         return (long)value;
1146     }
1147 
1148     /**
1149      * Returns the value of this {@code Integer} as a {@code float}
1150      * after a widening primitive conversion.
1151      * @jls 5.1.2 Widening Primitive Conversions
1152      */
1153     public float floatValue() {
1154         return (float)value;
1155     }
1156 
1157     /**
1158      * Returns the value of this {@code Integer} as a {@code double}
1159      * after a widening primitive conversion.
1160      * @jls 5.1.2 Widening Primitive Conversions
1161      */
1162     public double doubleValue() {
1163         return (double)value;
1164     }
1165 
1166     /**
1167      * Returns a {@code String} object representing this
1168      * {@code Integer}'s value. The value is converted to signed
1169      * decimal representation and returned as a string, exactly as if
1170      * the integer value were given as an argument to the {@link
1171      * java.lang.Integer#toString(int)} method.
1172      *
1173      * @return  a string representation of the value of this object in
1174      *          base&nbsp;10.
1175      */
1176     public String toString() {
1177         return toString(value);
1178     }
1179 
1180     /**
1181      * Returns a hash code for this {@code Integer}.
1182      *
1183      * @return  a hash code value for this object, equal to the
1184      *          primitive {@code int} value represented by this
1185      *          {@code Integer} object.
1186      */
1187     @Override
1188     public int hashCode() {
1189         return Integer.hashCode(value);
1190     }
1191 
1192     /**
1193      * Returns a hash code for a {@code int} value; compatible with
1194      * {@code Integer.hashCode()}.
1195      *
1196      * @param value the value to hash
1197      * @since 1.8
1198      *
1199      * @return a hash code value for a {@code int} value.
1200      */
1201     public static int hashCode(int value) {
1202         return value;
1203     }
1204 
1205     /**
1206      * Compares this object to the specified object.  The result is
1207      * {@code true} if and only if the argument is not
1208      * {@code null} and is an {@code Integer} object that
1209      * contains the same {@code int} value as this object.
1210      *
1211      * @param   obj   the object to compare with.
1212      * @return  {@code true} if the objects are the same;
1213      *          {@code false} otherwise.
1214      */
1215     public boolean equals(Object obj) {
1216         if (obj instanceof Integer) {
1217             return value == ((Integer)obj).intValue();
1218         }
1219         return false;
1220     }
1221 
1222     /**
1223      * Determines the integer value of the system property with the
1224      * specified name.
1225      *
1226      * <p>The first argument is treated as the name of a system
1227      * property.  System properties are accessible through the {@link
1228      * java.lang.System#getProperty(java.lang.String)} method. The
1229      * string value of this property is then interpreted as an integer
1230      * value using the grammar supported by {@link Integer#decode decode} and
1231      * an {@code Integer} object representing this value is returned.
1232      *
1233      * <p>If there is no property with the specified name, if the
1234      * specified name is empty or {@code null}, or if the property
1235      * does not have the correct numeric format, then {@code null} is
1236      * returned.
1237      *
1238      * <p>In other words, this method returns an {@code Integer}
1239      * object equal to the value of:
1240      *
1241      * <blockquote>
1242      *  {@code getInteger(nm, null)}
1243      * </blockquote>
1244      *
1245      * @param   nm   property name.
1246      * @return  the {@code Integer} value of the property.
1247      * @throws  SecurityException for the same reasons as
1248      *          {@link System#getProperty(String) System.getProperty}
1249      * @see     java.lang.System#getProperty(java.lang.String)
1250      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1251      */
1252     public static Integer getInteger(String nm) {
1253         return getInteger(nm, null);
1254     }
1255 
1256     /**
1257      * Determines the integer value of the system property with the
1258      * specified name.
1259      *
1260      * <p>The first argument is treated as the name of a system
1261      * property.  System properties are accessible through the {@link
1262      * java.lang.System#getProperty(java.lang.String)} method. The
1263      * string value of this property is then interpreted as an integer
1264      * value using the grammar supported by {@link Integer#decode decode} and
1265      * an {@code Integer} object representing this value is returned.
1266      *
1267      * <p>The second argument is the default value. An {@code Integer} object
1268      * that represents the value of the second argument is returned if there
1269      * is no property of the specified name, if the property does not have
1270      * the correct numeric format, or if the specified name is empty or
1271      * {@code null}.
1272      *
1273      * <p>In other words, this method returns an {@code Integer} object
1274      * equal to the value of:
1275      *
1276      * <blockquote>
1277      *  {@code getInteger(nm, new Integer(val))}
1278      * </blockquote>
1279      *
1280      * but in practice it may be implemented in a manner such as:
1281      *
1282      * <blockquote><pre>
1283      * Integer result = getInteger(nm, null);
1284      * return (result == null) ? new Integer(val) : result;
1285      * </pre></blockquote>
1286      *
1287      * to avoid the unnecessary allocation of an {@code Integer}
1288      * object when the default value is not needed.
1289      *
1290      * @param   nm   property name.
1291      * @param   val   default value.
1292      * @return  the {@code Integer} value of the property.
1293      * @throws  SecurityException for the same reasons as
1294      *          {@link System#getProperty(String) System.getProperty}
1295      * @see     java.lang.System#getProperty(java.lang.String)
1296      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1297      */
1298     public static Integer getInteger(String nm, int val) {
1299         Integer result = getInteger(nm, null);
1300         return (result == null) ? Integer.valueOf(val) : result;
1301     }
1302 
1303     /**
1304      * Returns the integer value of the system property with the
1305      * specified name.  The first argument is treated as the name of a
1306      * system property.  System properties are accessible through the
1307      * {@link java.lang.System#getProperty(java.lang.String)} method.
1308      * The string value of this property is then interpreted as an
1309      * integer value, as per the {@link Integer#decode decode} method,
1310      * and an {@code Integer} object representing this value is
1311      * returned; in summary:
1312      *
1313      * <ul><li>If the property value begins with the two ASCII characters
1314      *         {@code 0x} or the ASCII character {@code #}, not
1315      *      followed by a minus sign, then the rest of it is parsed as a
1316      *      hexadecimal integer exactly as by the method
1317      *      {@link #valueOf(java.lang.String, int)} with radix 16.
1318      * <li>If the property value begins with the ASCII character
1319      *     {@code 0} followed by another character, it is parsed as an
1320      *     octal integer exactly as by the method
1321      *     {@link #valueOf(java.lang.String, int)} with radix 8.
1322      * <li>Otherwise, the property value is parsed as a decimal integer
1323      * exactly as by the method {@link #valueOf(java.lang.String, int)}
1324      * with radix 10.
1325      * </ul>
1326      *
1327      * <p>The second argument is the default value. The default value is
1328      * returned if there is no property of the specified name, if the
1329      * property does not have the correct numeric format, or if the
1330      * specified name is empty or {@code null}.
1331      *
1332      * @param   nm   property name.
1333      * @param   val   default value.
1334      * @return  the {@code Integer} value of the property.
1335      * @throws  SecurityException for the same reasons as
1336      *          {@link System#getProperty(String) System.getProperty}
1337      * @see     System#getProperty(java.lang.String)
1338      * @see     System#getProperty(java.lang.String, java.lang.String)
1339      */
1340     public static Integer getInteger(String nm, Integer val) {
1341         String v = null;
1342         try {
1343             v = System.getProperty(nm);
1344         } catch (IllegalArgumentException | NullPointerException e) {
1345         }
1346         if (v != null) {
1347             try {
1348                 return Integer.decode(v);
1349             } catch (NumberFormatException e) {
1350             }
1351         }
1352         return val;
1353     }
1354 
1355     /**
1356      * Decodes a {@code String} into an {@code Integer}.
1357      * Accepts decimal, hexadecimal, and octal numbers given
1358      * by the following grammar:
1359      *
1360      * <blockquote>
1361      * <dl>
1362      * <dt><i>DecodableString:</i>
1363      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1364      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1365      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1366      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1367      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1368      *
1369      * <dt><i>Sign:</i>
1370      * <dd>{@code -}
1371      * <dd>{@code +}
1372      * </dl>
1373      * </blockquote>
1374      *
1375      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1376      * are as defined in section 3.10.1 of
1377      * <cite>The Java&trade; Language Specification</cite>,
1378      * except that underscores are not accepted between digits.
1379      *
1380      * <p>The sequence of characters following an optional
1381      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1382      * "{@code #}", or leading zero) is parsed as by the {@code
1383      * Integer.parseInt} method with the indicated radix (10, 16, or
1384      * 8).  This sequence of characters must represent a positive
1385      * value or a {@link NumberFormatException} will be thrown.  The
1386      * result is negated if first character of the specified {@code
1387      * String} is the minus sign.  No whitespace characters are
1388      * permitted in the {@code String}.
1389      *
1390      * @param     nm the {@code String} to decode.
1391      * @return    an {@code Integer} object holding the {@code int}
1392      *             value represented by {@code nm}
1393      * @exception NumberFormatException  if the {@code String} does not
1394      *            contain a parsable integer.
1395      * @see java.lang.Integer#parseInt(java.lang.String, int)
1396      */
1397     public static Integer decode(String nm) throws NumberFormatException {
1398         int radix = 10;
1399         int index = 0;
1400         boolean negative = false;
1401         Integer result;
1402 
1403         if (nm.length() == 0)
1404             throw new NumberFormatException("Zero length string");
1405         char firstChar = nm.charAt(0);
1406         // Handle sign, if present
1407         if (firstChar == '-') {
1408             negative = true;
1409             index++;
1410         } else if (firstChar == '+')
1411             index++;
1412 
1413         // Handle radix specifier, if present
1414         if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1415             index += 2;
1416             radix = 16;
1417         }
1418         else if (nm.startsWith("#", index)) {
1419             index ++;
1420             radix = 16;
1421         }
1422         else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1423             index ++;
1424             radix = 8;
1425         }
1426 
1427         if (nm.startsWith("-", index) || nm.startsWith("+", index))
1428             throw new NumberFormatException("Sign character in wrong position");
1429 
1430         try {
1431             result = Integer.valueOf(nm.substring(index), radix);
1432             result = negative ? Integer.valueOf(-result.intValue()) : result;
1433         } catch (NumberFormatException e) {
1434             // If number is Integer.MIN_VALUE, we'll end up here. The next line
1435             // handles this case, and causes any genuine format error to be
1436             // rethrown.
1437             String constant = negative ? ("-" + nm.substring(index))
1438                                        : nm.substring(index);
1439             result = Integer.valueOf(constant, radix);
1440         }
1441         return result;
1442     }
1443 
1444     /**
1445      * Compares two {@code Integer} objects numerically.
1446      *
1447      * @param   anotherInteger   the {@code Integer} to be compared.
1448      * @return  the value {@code 0} if this {@code Integer} is
1449      *          equal to the argument {@code Integer}; a value less than
1450      *          {@code 0} if this {@code Integer} is numerically less
1451      *          than the argument {@code Integer}; and a value greater
1452      *          than {@code 0} if this {@code Integer} is numerically
1453      *           greater than the argument {@code Integer} (signed
1454      *           comparison).
1455      * @since   1.2
1456      */
1457     public int compareTo(Integer anotherInteger) {
1458         return compare(this.value, anotherInteger.value);
1459     }
1460 
1461     /**
1462      * Compares two {@code int} values numerically.
1463      * The value returned is identical to what would be returned by:
1464      * <pre>
1465      *    Integer.valueOf(x).compareTo(Integer.valueOf(y))
1466      * </pre>
1467      *
1468      * @param  x the first {@code int} to compare
1469      * @param  y the second {@code int} to compare
1470      * @return the value {@code 0} if {@code x == y};
1471      *         a value less than {@code 0} if {@code x < y}; and
1472      *         a value greater than {@code 0} if {@code x > y}
1473      * @since 1.7
1474      */
1475     public static int compare(int x, int y) {
1476         return (x < y) ? -1 : ((x == y) ? 0 : 1);
1477     }
1478 
1479     /**
1480      * Compares two {@code int} values numerically treating the values
1481      * as unsigned.
1482      *
1483      * @param  x the first {@code int} to compare
1484      * @param  y the second {@code int} to compare
1485      * @return the value {@code 0} if {@code x == y}; a value less
1486      *         than {@code 0} if {@code x < y} as unsigned values; and
1487      *         a value greater than {@code 0} if {@code x > y} as
1488      *         unsigned values
1489      * @since 1.8
1490      */
1491     public static int compareUnsigned(int x, int y) {
1492         return compare(x + MIN_VALUE, y + MIN_VALUE);
1493     }
1494 
1495     /**
1496      * Converts the argument to a {@code long} by an unsigned
1497      * conversion.  In an unsigned conversion to a {@code long}, the
1498      * high-order 32 bits of the {@code long} are zero and the
1499      * low-order 32 bits are equal to the bits of the integer
1500      * argument.
1501      *
1502      * Consequently, zero and positive {@code int} values are mapped
1503      * to a numerically equal {@code long} value and negative {@code
1504      * int} values are mapped to a {@code long} value equal to the
1505      * input plus 2<sup>32</sup>.
1506      *
1507      * @param  x the value to convert to an unsigned {@code long}
1508      * @return the argument converted to {@code long} by an unsigned
1509      *         conversion
1510      * @since 1.8
1511      */
1512     public static long toUnsignedLong(int x) {
1513         return ((long) x) & 0xffffffffL;
1514     }
1515 
1516     /**
1517      * Returns the unsigned quotient of dividing the first argument by
1518      * the second where each argument and the result is interpreted as
1519      * an unsigned value.
1520      *
1521      * <p>Note that in two's complement arithmetic, the three other
1522      * basic arithmetic operations of add, subtract, and multiply are
1523      * bit-wise identical if the two operands are regarded as both
1524      * being signed or both being unsigned.  Therefore separate {@code
1525      * addUnsigned}, etc. methods are not provided.
1526      *
1527      * @param dividend the value to be divided
1528      * @param divisor the value doing the dividing
1529      * @return the unsigned quotient of the first argument divided by
1530      * the second argument
1531      * @see #remainderUnsigned
1532      * @since 1.8
1533      */
1534     public static int divideUnsigned(int dividend, int divisor) {
1535         // In lieu of tricky code, for now just use long arithmetic.
1536         return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1537     }
1538 
1539     /**
1540      * Returns the unsigned remainder from dividing the first argument
1541      * by the second where each argument and the result is interpreted
1542      * as an unsigned value.
1543      *
1544      * @param dividend the value to be divided
1545      * @param divisor the value doing the dividing
1546      * @return the unsigned remainder of the first argument divided by
1547      * the second argument
1548      * @see #divideUnsigned
1549      * @since 1.8
1550      */
1551     public static int remainderUnsigned(int dividend, int divisor) {
1552         // In lieu of tricky code, for now just use long arithmetic.
1553         return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1554     }
1555 
1556 
1557     // Bit twiddling
1558 
1559     /**
1560      * The number of bits used to represent an {@code int} value in two's
1561      * complement binary form.
1562      *
1563      * @since 1.5
1564      */
1565     @Native public static final int SIZE = 32;
1566 
1567     /**
1568      * The number of bytes used to represent a {@code int} value in two's
1569      * complement binary form.
1570      *
1571      * @since 1.8
1572      */
1573     public static final int BYTES = SIZE / Byte.SIZE;
1574 
1575     /**
1576      * Returns an {@code int} value with at most a single one-bit, in the
1577      * position of the highest-order ("leftmost") one-bit in the specified
1578      * {@code int} value.  Returns zero if the specified value has no
1579      * one-bits in its two's complement binary representation, that is, if it
1580      * is equal to zero.
1581      *
1582      * @param i the value whose highest one bit is to be computed
1583      * @return an {@code int} value with a single one-bit, in the position
1584      *     of the highest-order one-bit in the specified value, or zero if
1585      *     the specified value is itself equal to zero.
1586      * @since 1.5
1587      */
1588     public static int highestOneBit(int i) {
1589         // HD, Figure 3-1
1590         i |= (i >>  1);
1591         i |= (i >>  2);
1592         i |= (i >>  4);
1593         i |= (i >>  8);
1594         i |= (i >> 16);
1595         return i - (i >>> 1);
1596     }
1597 
1598     /**
1599      * Returns an {@code int} value with at most a single one-bit, in the
1600      * position of the lowest-order ("rightmost") one-bit in the specified
1601      * {@code int} value.  Returns zero if the specified value has no
1602      * one-bits in its two's complement binary representation, that is, if it
1603      * is equal to zero.
1604      *
1605      * @param i the value whose lowest one bit is to be computed
1606      * @return an {@code int} value with a single one-bit, in the position
1607      *     of the lowest-order one-bit in the specified value, or zero if
1608      *     the specified value is itself equal to zero.
1609      * @since 1.5
1610      */
1611     public static int lowestOneBit(int i) {
1612         // HD, Section 2-1
1613         return i & -i;
1614     }
1615 
1616     /**
1617      * Returns the number of zero bits preceding the highest-order
1618      * ("leftmost") one-bit in the two's complement binary representation
1619      * of the specified {@code int} value.  Returns 32 if the
1620      * specified value has no one-bits in its two's complement representation,
1621      * in other words if it is equal to zero.
1622      *
1623      * <p>Note that this method is closely related to the logarithm base 2.
1624      * For all positive {@code int} values x:
1625      * <ul>
1626      * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1627      * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1628      * </ul>
1629      *
1630      * @param i the value whose number of leading zeros is to be computed
1631      * @return the number of zero bits preceding the highest-order
1632      *     ("leftmost") one-bit in the two's complement binary representation
1633      *     of the specified {@code int} value, or 32 if the value
1634      *     is equal to zero.
1635      * @since 1.5
1636      */
1637     @HotSpotIntrinsicCandidate
1638     public static int numberOfLeadingZeros(int i) {
1639         // HD, Figure 5-6
1640         if (i == 0)
1641             return 32;
1642         int n = 1;
1643         if (i >>> 16 == 0) { n += 16; i <<= 16; }
1644         if (i >>> 24 == 0) { n +=  8; i <<=  8; }
1645         if (i >>> 28 == 0) { n +=  4; i <<=  4; }
1646         if (i >>> 30 == 0) { n +=  2; i <<=  2; }
1647         n -= i >>> 31;
1648         return n;
1649     }
1650 
1651     /**
1652      * Returns the number of zero bits following the lowest-order ("rightmost")
1653      * one-bit in the two's complement binary representation of the specified
1654      * {@code int} value.  Returns 32 if the specified value has no
1655      * one-bits in its two's complement representation, in other words if it is
1656      * equal to zero.
1657      *
1658      * @param i the value whose number of trailing zeros is to be computed
1659      * @return the number of zero bits following the lowest-order ("rightmost")
1660      *     one-bit in the two's complement binary representation of the
1661      *     specified {@code int} value, or 32 if the value is equal
1662      *     to zero.
1663      * @since 1.5
1664      */
1665     @HotSpotIntrinsicCandidate
1666     public static int numberOfTrailingZeros(int i) {
1667         // HD, Figure 5-14
1668         int y;
1669         if (i == 0) return 32;
1670         int n = 31;
1671         y = i <<16; if (y != 0) { n = n -16; i = y; }
1672         y = i << 8; if (y != 0) { n = n - 8; i = y; }
1673         y = i << 4; if (y != 0) { n = n - 4; i = y; }
1674         y = i << 2; if (y != 0) { n = n - 2; i = y; }
1675         return n - ((i << 1) >>> 31);
1676     }
1677 
1678     /**
1679      * Returns the number of one-bits in the two's complement binary
1680      * representation of the specified {@code int} value.  This function is
1681      * sometimes referred to as the <i>population count</i>.
1682      *
1683      * @param i the value whose bits are to be counted
1684      * @return the number of one-bits in the two's complement binary
1685      *     representation of the specified {@code int} value.
1686      * @since 1.5
1687      */
1688     @HotSpotIntrinsicCandidate
1689     public static int bitCount(int i) {
1690         // HD, Figure 5-2
1691         i = i - ((i >>> 1) & 0x55555555);
1692         i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1693         i = (i + (i >>> 4)) & 0x0f0f0f0f;
1694         i = i + (i >>> 8);
1695         i = i + (i >>> 16);
1696         return i & 0x3f;
1697     }
1698 
1699     /**
1700      * Returns the value obtained by rotating the two's complement binary
1701      * representation of the specified {@code int} value left by the
1702      * specified number of bits.  (Bits shifted out of the left hand, or
1703      * high-order, side reenter on the right, or low-order.)
1704      *
1705      * <p>Note that left rotation with a negative distance is equivalent to
1706      * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1707      * distance)}.  Note also that rotation by any multiple of 32 is a
1708      * no-op, so all but the last five bits of the rotation distance can be
1709      * ignored, even if the distance is negative: {@code rotateLeft(val,
1710      * distance) == rotateLeft(val, distance & 0x1F)}.
1711      *
1712      * @param i the value whose bits are to be rotated left
1713      * @param distance the number of bit positions to rotate left
1714      * @return the value obtained by rotating the two's complement binary
1715      *     representation of the specified {@code int} value left by the
1716      *     specified number of bits.
1717      * @since 1.5
1718      */
1719     public static int rotateLeft(int i, int distance) {
1720         return (i << distance) | (i >>> -distance);
1721     }
1722 
1723     /**
1724      * Returns the value obtained by rotating the two's complement binary
1725      * representation of the specified {@code int} value right by the
1726      * specified number of bits.  (Bits shifted out of the right hand, or
1727      * low-order, side reenter on the left, or high-order.)
1728      *
1729      * <p>Note that right rotation with a negative distance is equivalent to
1730      * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1731      * distance)}.  Note also that rotation by any multiple of 32 is a
1732      * no-op, so all but the last five bits of the rotation distance can be
1733      * ignored, even if the distance is negative: {@code rotateRight(val,
1734      * distance) == rotateRight(val, distance & 0x1F)}.
1735      *
1736      * @param i the value whose bits are to be rotated right
1737      * @param distance the number of bit positions to rotate right
1738      * @return the value obtained by rotating the two's complement binary
1739      *     representation of the specified {@code int} value right by the
1740      *     specified number of bits.
1741      * @since 1.5
1742      */
1743     public static int rotateRight(int i, int distance) {
1744         return (i >>> distance) | (i << -distance);
1745     }
1746 
1747     /**
1748      * Returns the value obtained by reversing the order of the bits in the
1749      * two's complement binary representation of the specified {@code int}
1750      * value.
1751      *
1752      * @param i the value to be reversed
1753      * @return the value obtained by reversing order of the bits in the
1754      *     specified {@code int} value.
1755      * @since 1.5
1756      */
1757     public static int reverse(int i) {
1758         // HD, Figure 7-1
1759         i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1760         i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1761         i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1762         i = (i << 24) | ((i & 0xff00) << 8) |
1763             ((i >>> 8) & 0xff00) | (i >>> 24);
1764         return i;
1765     }
1766 
1767     /**
1768      * Returns the signum function of the specified {@code int} value.  (The
1769      * return value is -1 if the specified value is negative; 0 if the
1770      * specified value is zero; and 1 if the specified value is positive.)
1771      *
1772      * @param i the value whose signum is to be computed
1773      * @return the signum function of the specified {@code int} value.
1774      * @since 1.5
1775      */
1776     public static int signum(int i) {
1777         // HD, Section 2-7
1778         return (i >> 31) | (-i >>> 31);
1779     }
1780 
1781     /**
1782      * Returns the value obtained by reversing the order of the bytes in the
1783      * two's complement representation of the specified {@code int} value.
1784      *
1785      * @param i the value whose bytes are to be reversed
1786      * @return the value obtained by reversing the bytes in the specified
1787      *     {@code int} value.
1788      * @since 1.5
1789      */
1790     @HotSpotIntrinsicCandidate
1791     public static int reverseBytes(int i) {
1792         return ((i >>> 24)           ) |
1793                ((i >>   8) &   0xFF00) |
1794                ((i <<   8) & 0xFF0000) |
1795                ((i << 24));
1796     }
1797 
1798     /**
1799      * Adds two integers together as per the + operator.
1800      *
1801      * @param a the first operand
1802      * @param b the second operand
1803      * @return the sum of {@code a} and {@code b}
1804      * @see java.util.function.BinaryOperator
1805      * @since 1.8
1806      */
1807     public static int sum(int a, int b) {
1808         return a + b;
1809     }
1810 
1811     /**
1812      * Returns the greater of two {@code int} values
1813      * as if by calling {@link Math#max(int, int) Math.max}.
1814      *
1815      * @param a the first operand
1816      * @param b the second operand
1817      * @return the greater of {@code a} and {@code b}
1818      * @see java.util.function.BinaryOperator
1819      * @since 1.8
1820      */
1821     public static int max(int a, int b) {
1822         return Math.max(a, b);
1823     }
1824 
1825     /**
1826      * Returns the smaller of two {@code int} values
1827      * as if by calling {@link Math#min(int, int) Math.min}.
1828      *
1829      * @param a the first operand
1830      * @param b the second operand
1831      * @return the smaller of {@code a} and {@code b}
1832      * @see java.util.function.BinaryOperator
1833      * @since 1.8
1834      */
1835     public static int min(int a, int b) {
1836         return Math.min(a, b);
1837     }
1838 
1839     /** use serialVersionUID from JDK 1.0.2 for interoperability */
1840     @Native private static final long serialVersionUID = 1360826667806852920L;
1841 }