rev 14560 : Merge

   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 import jdk.internal.misc.VM;
  32 
  33 import static java.lang.String.COMPACT_STRINGS;
  34 import static java.lang.String.LATIN1;
  35 import static java.lang.String.UTF16;
  36 
  37 /**
  38  * The {@code Integer} class wraps a value of the primitive type
  39  * {@code int} in an object. An object of type {@code Integer}
  40  * contains a single field whose type is {@code int}.
  41  *
  42  * <p>In addition, this class provides several methods for converting
  43  * an {@code int} to a {@code String} and a {@code String} to an
  44  * {@code int}, as well as other constants and methods useful when
  45  * dealing with an {@code int}.
  46  *
  47  * <p>Implementation note: The implementations of the "bit twiddling"
  48  * methods (such as {@link #highestOneBit(int) highestOneBit} and
  49  * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
  50  * based on material from Henry S. Warren, Jr.'s <i>Hacker's
  51  * Delight</i>, (Addison Wesley, 2002).
  52  *
  53  * @author  Lee Boynton
  54  * @author  Arthur van Hoff
  55  * @author  Josh Bloch
  56  * @author  Joseph D. Darcy
  57  * @since 1.0
  58  */
  59 public final class Integer extends Number implements Comparable<Integer> {
  60     /**
  61      * A constant holding the minimum value an {@code int} can
  62      * have, -2<sup>31</sup>.
  63      */
  64     @Native public static final int   MIN_VALUE = 0x80000000;
  65 
  66     /**
  67      * A constant holding the maximum value an {@code int} can
  68      * have, 2<sup>31</sup>-1.
  69      */
  70     @Native public static final int   MAX_VALUE = 0x7fffffff;
  71 
  72     /**
  73      * The {@code Class} instance representing the primitive type
  74      * {@code int}.
  75      *
  76      * @since   1.1
  77      */
  78     @SuppressWarnings("unchecked")
  79     public static final Class<Integer>  TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
  80 
  81     /**
  82      * All possible chars for representing a number as a String
  83      */
  84     static final char[] digits = {
  85         '0' , '1' , '2' , '3' , '4' , '5' ,
  86         '6' , '7' , '8' , '9' , 'a' , 'b' ,
  87         'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
  88         'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
  89         'o' , 'p' , 'q' , 'r' , 's' , 't' ,
  90         'u' , 'v' , 'w' , 'x' , 'y' , 'z'
  91     };
  92 
  93     /**
  94      * Returns a string representation of the first argument in the
  95      * radix specified by the second argument.
  96      *
  97      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
  98      * or larger than {@code Character.MAX_RADIX}, then the radix
  99      * {@code 10} is used instead.
 100      *
 101      * <p>If the first argument is negative, the first element of the
 102      * result is the ASCII minus character {@code '-'}
 103      * ({@code '\u005Cu002D'}). If the first argument is not
 104      * negative, no sign character appears in the result.
 105      *
 106      * <p>The remaining characters of the result represent the magnitude
 107      * of the first argument. If the magnitude is zero, it is
 108      * represented by a single zero character {@code '0'}
 109      * ({@code '\u005Cu0030'}); otherwise, the first character of
 110      * the representation of the magnitude will not be the zero
 111      * character.  The following ASCII characters are used as digits:
 112      *
 113      * <blockquote>
 114      *   {@code 0123456789abcdefghijklmnopqrstuvwxyz}
 115      * </blockquote>
 116      *
 117      * These are {@code '\u005Cu0030'} through
 118      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 119      * {@code '\u005Cu007A'}. If {@code radix} is
 120      * <var>N</var>, then the first <var>N</var> of these characters
 121      * are used as radix-<var>N</var> digits in the order shown. Thus,
 122      * the digits for hexadecimal (radix 16) are
 123      * {@code 0123456789abcdef}. If uppercase letters are
 124      * desired, the {@link java.lang.String#toUpperCase()} method may
 125      * be called on the result:
 126      *
 127      * <blockquote>
 128      *  {@code Integer.toString(n, 16).toUpperCase()}
 129      * </blockquote>
 130      *
 131      * @param   i       an integer to be converted to a string.
 132      * @param   radix   the radix to use in the string representation.
 133      * @return  a string representation of the argument in the specified radix.
 134      * @see     java.lang.Character#MAX_RADIX
 135      * @see     java.lang.Character#MIN_RADIX
 136      */
 137     public static String toString(int i, int radix) {
 138         if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
 139             radix = 10;
 140 
 141         /* Use the faster version */
 142         if (radix == 10) {
 143             return toString(i);
 144         }
 145 
 146         if (COMPACT_STRINGS) {
 147             byte[] buf = new byte[33];
 148             boolean negative = (i < 0);
 149             int charPos = 32;
 150 
 151             if (!negative) {
 152                 i = -i;
 153             }
 154 
 155             while (i <= -radix) {
 156                 buf[charPos--] = (byte)digits[-(i % radix)];
 157                 i = i / radix;
 158             }
 159             buf[charPos] = (byte)digits[-i];
 160 
 161             if (negative) {
 162                 buf[--charPos] = '-';
 163             }
 164 
 165             return StringLatin1.newString(buf, charPos, (33 - charPos));
 166         }
 167         return toStringUTF16(i, radix);
 168     }
 169 
 170     private static String toStringUTF16(int i, int radix) {
 171         byte[] buf = new byte[33 * 2];
 172         boolean negative = (i < 0);
 173         int charPos = 32;
 174         if (!negative) {
 175             i = -i;
 176         }
 177         while (i <= -radix) {
 178             StringUTF16.putChar(buf, charPos--, digits[-(i % radix)]);
 179             i = i / radix;
 180         }
 181         StringUTF16.putChar(buf, charPos, digits[-i]);
 182 
 183         if (negative) {
 184             StringUTF16.putChar(buf, --charPos, '-');
 185         }
 186         return StringUTF16.newString(buf, charPos, (33 - charPos));
 187     }
 188 
 189     /**
 190      * Returns a string representation of the first argument as an
 191      * unsigned integer value in the radix specified by the second
 192      * argument.
 193      *
 194      * <p>If the radix is smaller than {@code Character.MIN_RADIX}
 195      * or larger than {@code Character.MAX_RADIX}, then the radix
 196      * {@code 10} is used instead.
 197      *
 198      * <p>Note that since the first argument is treated as an unsigned
 199      * value, no leading sign character is printed.
 200      *
 201      * <p>If the magnitude is zero, it is represented by a single zero
 202      * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
 203      * the first character of the representation of the magnitude will
 204      * not be the zero character.
 205      *
 206      * <p>The behavior of radixes and the characters used as digits
 207      * are the same as {@link #toString(int, int) toString}.
 208      *
 209      * @param   i       an integer to be converted to an unsigned string.
 210      * @param   radix   the radix to use in the string representation.
 211      * @return  an unsigned string representation of the argument in the specified radix.
 212      * @see     #toString(int, int)
 213      * @since 1.8
 214      */
 215     public static String toUnsignedString(int i, int radix) {
 216         return Long.toUnsignedString(toUnsignedLong(i), radix);
 217     }
 218 
 219     /**
 220      * Returns a string representation of the integer argument as an
 221      * unsigned integer in base&nbsp;16.
 222      *
 223      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 224      * if the argument is negative; otherwise, it is equal to the
 225      * argument.  This value is converted to a string of ASCII digits
 226      * in hexadecimal (base&nbsp;16) with no extra leading
 227      * {@code 0}s.
 228      *
 229      * <p>The value of the argument can be recovered from the returned
 230      * string {@code s} by calling {@link
 231      * Integer#parseUnsignedInt(String, int)
 232      * Integer.parseUnsignedInt(s, 16)}.
 233      *
 234      * <p>If the unsigned magnitude is zero, it is represented by a
 235      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 236      * otherwise, the first character of the representation of the
 237      * unsigned magnitude will not be the zero character. The
 238      * following characters are used as hexadecimal digits:
 239      *
 240      * <blockquote>
 241      *  {@code 0123456789abcdef}
 242      * </blockquote>
 243      *
 244      * These are the characters {@code '\u005Cu0030'} through
 245      * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
 246      * {@code '\u005Cu0066'}. If uppercase letters are
 247      * desired, the {@link java.lang.String#toUpperCase()} method may
 248      * be called on the result:
 249      *
 250      * <blockquote>
 251      *  {@code Integer.toHexString(n).toUpperCase()}
 252      * </blockquote>
 253      *
 254      * @param   i   an integer to be converted to a string.
 255      * @return  the string representation of the unsigned integer value
 256      *          represented by the argument in hexadecimal (base&nbsp;16).
 257      * @see #parseUnsignedInt(String, int)
 258      * @see #toUnsignedString(int, int)
 259      * @since   1.0.2
 260      */
 261     public static String toHexString(int i) {
 262         return toUnsignedString0(i, 4);
 263     }
 264 
 265     /**
 266      * Returns a string representation of the integer argument as an
 267      * unsigned integer in base&nbsp;8.
 268      *
 269      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 270      * if the argument is negative; otherwise, it is equal to the
 271      * argument.  This value is converted to a string of ASCII digits
 272      * in octal (base&nbsp;8) with no extra leading {@code 0}s.
 273      *
 274      * <p>The value of the argument can be recovered from the returned
 275      * string {@code s} by calling {@link
 276      * Integer#parseUnsignedInt(String, int)
 277      * Integer.parseUnsignedInt(s, 8)}.
 278      *
 279      * <p>If the unsigned magnitude is zero, it is represented by a
 280      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 281      * otherwise, the first character of the representation of the
 282      * unsigned magnitude will not be the zero character. The
 283      * following characters are used as octal digits:
 284      *
 285      * <blockquote>
 286      * {@code 01234567}
 287      * </blockquote>
 288      *
 289      * These are the characters {@code '\u005Cu0030'} through
 290      * {@code '\u005Cu0037'}.
 291      *
 292      * @param   i   an integer to be converted to a string.
 293      * @return  the string representation of the unsigned integer value
 294      *          represented by the argument in octal (base&nbsp;8).
 295      * @see #parseUnsignedInt(String, int)
 296      * @see #toUnsignedString(int, int)
 297      * @since   1.0.2
 298      */
 299     public static String toOctalString(int i) {
 300         return toUnsignedString0(i, 3);
 301     }
 302 
 303     /**
 304      * Returns a string representation of the integer argument as an
 305      * unsigned integer in base&nbsp;2.
 306      *
 307      * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
 308      * if the argument is negative; otherwise it is equal to the
 309      * argument.  This value is converted to a string of ASCII digits
 310      * in binary (base&nbsp;2) with no extra leading {@code 0}s.
 311      *
 312      * <p>The value of the argument can be recovered from the returned
 313      * string {@code s} by calling {@link
 314      * Integer#parseUnsignedInt(String, int)
 315      * Integer.parseUnsignedInt(s, 2)}.
 316      *
 317      * <p>If the unsigned magnitude is zero, it is represented by a
 318      * single zero character {@code '0'} ({@code '\u005Cu0030'});
 319      * otherwise, the first character of the representation of the
 320      * unsigned magnitude will not be the zero character. The
 321      * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
 322      * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
 323      *
 324      * @param   i   an integer to be converted to a string.
 325      * @return  the string representation of the unsigned integer value
 326      *          represented by the argument in binary (base&nbsp;2).
 327      * @see #parseUnsignedInt(String, int)
 328      * @see #toUnsignedString(int, int)
 329      * @since   1.0.2
 330      */
 331     public static String toBinaryString(int i) {
 332         return toUnsignedString0(i, 1);
 333     }
 334 
 335     /**
 336      * Convert the integer to an unsigned number.
 337      */
 338     private static String toUnsignedString0(int val, int shift) {
 339         // assert shift > 0 && shift <=5 : "Illegal shift value";
 340         int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
 341         int chars = Math.max(((mag + (shift - 1)) / shift), 1);
 342 
 343         if (COMPACT_STRINGS) {
 344             byte[] buf = new byte[chars];
 345             formatUnsignedInt(val, shift, buf, 0, chars);
 346             return new String(buf, LATIN1);
 347         } else {
 348             byte[] buf = new byte[chars * 2];
 349             formatUnsignedIntUTF16(val, shift, buf, 0, chars);
 350             return new String(buf, UTF16);
 351         }
 352     }
 353 
 354     /**
 355      * Format an {@code int} (treated as unsigned) into a character buffer. If
 356      * {@code len} exceeds the formatted ASCII representation of {@code val},
 357      * {@code buf} will be padded with leading zeroes.
 358      *
 359      * @param val the unsigned int to format
 360      * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
 361      * @param buf the character buffer to write to
 362      * @param offset the offset in the destination buffer to start at
 363      * @param len the number of characters to write
 364      */
 365     static void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
 366         // assert shift > 0 && shift <=5 : "Illegal shift value";
 367         // assert offset >= 0 && offset < buf.length : "illegal offset";
 368         // assert len > 0 && (offset + len) <= buf.length : "illegal length";
 369         int charPos = offset + len;
 370         int radix = 1 << shift;
 371         int mask = radix - 1;
 372         do {
 373             buf[--charPos] = Integer.digits[val & mask];
 374             val >>>= shift;
 375         } while (charPos > offset);
 376     }
 377 
 378     /** byte[]/LATIN1 version    */
 379     static void formatUnsignedInt(int val, int shift, byte[] buf, int offset, int len) {
 380         int charPos = offset + len;
 381         int radix = 1 << shift;
 382         int mask = radix - 1;
 383         do {
 384             buf[--charPos] = (byte)Integer.digits[val & mask];
 385             val >>>= shift;
 386         } while (charPos > offset);
 387     }
 388 
 389     /** byte[]/UTF16 version    */
 390     static void formatUnsignedIntUTF16(int val, int shift, byte[] buf, int offset, int len) {
 391         int charPos = offset + len;
 392         int radix = 1 << shift;
 393         int mask = radix - 1;
 394         do {
 395             StringUTF16.putChar(buf, --charPos, Integer.digits[val & mask]);
 396             val >>>= shift;
 397         } while (charPos > offset);
 398     }
 399 
 400     static final byte[] DigitTens = {
 401         '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
 402         '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
 403         '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
 404         '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
 405         '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
 406         '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
 407         '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
 408         '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
 409         '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
 410         '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
 411         } ;
 412 
 413     static final byte[] DigitOnes = {
 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         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 424         } ;
 425 
 426 
 427     /**
 428      * Returns a {@code String} object representing the
 429      * specified integer. The argument is converted to signed decimal
 430      * representation and returned as a string, exactly as if the
 431      * argument and radix 10 were given as arguments to the {@link
 432      * #toString(int, int)} method.
 433      *
 434      * @param   i   an integer to be converted.
 435      * @return  a string representation of the argument in base&nbsp;10.
 436      */
 437     @HotSpotIntrinsicCandidate
 438     public static String toString(int i) {
 439         int size = stringSize(i);
 440         if (COMPACT_STRINGS) {
 441             byte[] buf = new byte[size];
 442             getChars(i, size, buf);
 443             return new String(buf, LATIN1);
 444         } else {
 445             byte[] buf = new byte[size * 2];
 446             getCharsUTF16(i, size, buf);
 447             return new String(buf, UTF16);
 448         }
 449     }
 450 
 451     /**
 452      * Returns a string representation of the argument as an unsigned
 453      * decimal value.
 454      *
 455      * The argument is converted to unsigned decimal representation
 456      * and returned as a string exactly as if the argument and radix
 457      * 10 were given as arguments to the {@link #toUnsignedString(int,
 458      * int)} method.
 459      *
 460      * @param   i  an integer to be converted to an unsigned string.
 461      * @return  an unsigned string representation of the argument.
 462      * @see     #toUnsignedString(int, int)
 463      * @since 1.8
 464      */
 465     public static String toUnsignedString(int i) {
 466         return Long.toString(toUnsignedLong(i));
 467     }
 468 
 469     /**
 470      * Places characters representing the integer i into the
 471      * character array buf. The characters are placed into
 472      * the buffer backwards starting with the least significant
 473      * digit at the specified index (exclusive), and working
 474      * backwards from there.
 475      *
 476      * @implNote This method converts positive inputs into negative
 477      * values, to cover the Integer.MIN_VALUE case. Converting otherwise
 478      * (negative to positive) will expose -Integer.MIN_VALUE that overflows
 479      * integer.





 480      */
 481     static void getChars(int i, int index, byte[] buf) {
 482         int q, r;
 483         int charPos = index;
 484 
 485         boolean negative = i < 0;
 486         if (!negative) {
 487             i = -i;
 488         }
 489 
 490         // Generate two digits per iteration
 491         while (i <= -100) {
 492             q = i / 100;
 493             r = (q * 100) - i;
 494             i = q;
 495             buf[--charPos] = DigitOnes[r];
 496             buf[--charPos] = DigitTens[r];
 497         }
 498 
 499         // We know there are at most two digits left at this point.
 500         q = i / 10;
 501         r = (q * 10) - i;
 502         buf[--charPos] = (byte)('0' + r);
 503 
 504         // Whatever left is the remaining digit.
 505         if (q < 0) {
 506             buf[--charPos] = (byte)('0' - q);
 507         }
 508 
 509         if (negative) {
 510             buf[--charPos] = (byte)'-';
 511         }

 512     }
 513 
 514     static void getCharsUTF16(int i, int index, byte[] buf) {









 515         int q, r;
 516         int charPos = index;
 517 
 518         boolean negative = (i < 0);
 519         if (!negative) {
 520             i = -i;
 521         }
 522 
 523         // Get 2 digits/iteration using ints
 524         while (i <= -100) {
 525             q = i / 100;
 526             r = (q * 100) - i;
 527             i = q;
 528             StringUTF16.putChar(buf, --charPos, DigitOnes[r]);
 529             StringUTF16.putChar(buf, --charPos, DigitTens[r]);
 530         }
 531 
 532         // We know there are at most two digits left at this point.
 533         q = i / 10;
 534         r = (q * 10) - i;
 535         StringUTF16.putChar(buf, --charPos, '0' + r);
 536 
 537         // Whatever left is the remaining digit.
 538         if (q < 0) {
 539             StringUTF16.putChar(buf, --charPos, '0' - q);
 540         }
 541 
 542         if (negative) {
 543             StringUTF16.putChar(buf, --charPos, '-');
 544         }

 545     }
 546 
 547     // Left here for compatibility reasons, see JDK-8143900.
 548     static final int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
 549                                       99999999, 999999999, Integer.MAX_VALUE };
 550 
 551     /**
 552      * Returns the string representation size for a given int value.
 553      *
 554      * @param x int value
 555      * @return string size
 556      *
 557      * @implNote There are other ways to compute this: e.g. binary search,
 558      * but values are biased heavily towards zero, and therefore linear search
 559      * wins. The iteration results are also routinely inlined in the generated
 560      * code after loop unrolling.
 561      */
 562     static int stringSize(int x) {
 563         int d = 1;
 564         if (x >= 0) {
 565             d = 0;
 566             x = -x;
 567         }
 568         int p = -10;
 569         for (int i = 1; i < 10; i++) {
 570             if (x > p)
 571                 return i + d;
 572             p = 10 * p;
 573         }
 574         return 10 + d;
 575     }
 576 
 577     /**
 578      * Parses the string argument as a signed integer in the radix
 579      * specified by the second argument. The characters in the string
 580      * must all be digits of the specified radix (as determined by
 581      * whether {@link java.lang.Character#digit(char, int)} returns a
 582      * nonnegative value), except that the first character may be an
 583      * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
 584      * indicate a negative value or an ASCII plus sign {@code '+'}
 585      * ({@code '\u005Cu002B'}) to indicate a positive value. The
 586      * resulting integer value is returned.
 587      *
 588      * <p>An exception of type {@code NumberFormatException} is
 589      * thrown if any of the following situations occurs:
 590      * <ul>
 591      * <li>The first argument is {@code null} or is a string of
 592      * length zero.
 593      *
 594      * <li>The radix is either smaller than
 595      * {@link java.lang.Character#MIN_RADIX} or
 596      * larger than {@link java.lang.Character#MAX_RADIX}.
 597      *
 598      * <li>Any character of the string is not a digit of the specified
 599      * radix, except that the first character may be a minus sign
 600      * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
 601      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 602      * string is longer than length 1.
 603      *
 604      * <li>The value represented by the string is not a value of type
 605      * {@code int}.
 606      * </ul>
 607      *
 608      * <p>Examples:
 609      * <blockquote><pre>
 610      * parseInt("0", 10) returns 0
 611      * parseInt("473", 10) returns 473
 612      * parseInt("+42", 10) returns 42
 613      * parseInt("-0", 10) returns 0
 614      * parseInt("-FF", 16) returns -255
 615      * parseInt("1100110", 2) returns 102
 616      * parseInt("2147483647", 10) returns 2147483647
 617      * parseInt("-2147483648", 10) returns -2147483648
 618      * parseInt("2147483648", 10) throws a NumberFormatException
 619      * parseInt("99", 8) throws a NumberFormatException
 620      * parseInt("Kona", 10) throws a NumberFormatException
 621      * parseInt("Kona", 27) returns 411787
 622      * </pre></blockquote>
 623      *
 624      * @param      s   the {@code String} containing the integer
 625      *                  representation to be parsed
 626      * @param      radix   the radix to be used while parsing {@code s}.
 627      * @return     the integer represented by the string argument in the
 628      *             specified radix.
 629      * @exception  NumberFormatException if the {@code String}
 630      *             does not contain a parsable {@code int}.
 631      */
 632     public static int parseInt(String s, int radix)
 633                 throws NumberFormatException
 634     {
 635         /*
 636          * WARNING: This method may be invoked early during VM initialization
 637          * before IntegerCache is initialized. Care must be taken to not use
 638          * the valueOf method.
 639          */
 640 
 641         if (s == null) {
 642             throw new NumberFormatException("null");
 643         }
 644 
 645         if (radix < Character.MIN_RADIX) {
 646             throw new NumberFormatException("radix " + radix +
 647                                             " less than Character.MIN_RADIX");
 648         }
 649 
 650         if (radix > Character.MAX_RADIX) {
 651             throw new NumberFormatException("radix " + radix +
 652                                             " greater than Character.MAX_RADIX");
 653         }
 654 
 655         boolean negative = false;
 656         int i = 0, len = s.length();
 657         int limit = -Integer.MAX_VALUE;
 658 
 659         if (len > 0) {
 660             char firstChar = s.charAt(0);
 661             if (firstChar < '0') { // Possible leading "+" or "-"
 662                 if (firstChar == '-') {
 663                     negative = true;
 664                     limit = Integer.MIN_VALUE;
 665                 } else if (firstChar != '+') {
 666                     throw NumberFormatException.forInputString(s);
 667                 }
 668 
 669                 if (len == 1) { // Cannot have lone "+" or "-"
 670                     throw NumberFormatException.forInputString(s);
 671                 }
 672                 i++;
 673             }
 674             int multmin = limit / radix;
 675             int result = 0;
 676             while (i < len) {
 677                 // Accumulating negatively avoids surprises near MAX_VALUE
 678                 int digit = Character.digit(s.charAt(i++), radix);
 679                 if (digit < 0 || result < multmin) {
 680                     throw NumberFormatException.forInputString(s);
 681                 }
 682                 result *= radix;
 683                 if (result < limit + digit) {
 684                     throw NumberFormatException.forInputString(s);
 685                 }
 686                 result -= digit;
 687             }
 688             return negative ? result : -result;
 689         } else {
 690             throw NumberFormatException.forInputString(s);
 691         }
 692     }
 693 
 694     /**
 695      * Parses the {@link CharSequence} argument as a signed {@code int} in the
 696      * specified {@code radix}, beginning at the specified {@code beginIndex}
 697      * and extending to {@code endIndex - 1}.
 698      *
 699      * <p>The method does not take steps to guard against the
 700      * {@code CharSequence} being mutated while parsing.
 701      *
 702      * @param      s   the {@code CharSequence} containing the {@code int}
 703      *                  representation to be parsed
 704      * @param      beginIndex   the beginning index, inclusive.
 705      * @param      endIndex     the ending index, exclusive.
 706      * @param      radix   the radix to be used while parsing {@code s}.
 707      * @return     the signed {@code int} represented by the subsequence in
 708      *             the specified radix.
 709      * @throws     NullPointerException  if {@code s} is null.
 710      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 711      *             negative, or if {@code beginIndex} is greater than
 712      *             {@code endIndex} or if {@code endIndex} is greater than
 713      *             {@code s.length()}.
 714      * @throws     NumberFormatException  if the {@code CharSequence} does not
 715      *             contain a parsable {@code int} in the specified
 716      *             {@code radix}, or if {@code radix} is either smaller than
 717      *             {@link java.lang.Character#MIN_RADIX} or larger than
 718      *             {@link java.lang.Character#MAX_RADIX}.
 719      * @since  9
 720      */
 721     public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix)
 722                 throws NumberFormatException {
 723         s = Objects.requireNonNull(s);
 724 
 725         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 726             throw new IndexOutOfBoundsException();
 727         }
 728         if (radix < Character.MIN_RADIX) {
 729             throw new NumberFormatException("radix " + radix +
 730                                             " less than Character.MIN_RADIX");
 731         }
 732         if (radix > Character.MAX_RADIX) {
 733             throw new NumberFormatException("radix " + radix +
 734                                             " greater than Character.MAX_RADIX");
 735         }
 736 
 737         boolean negative = false;
 738         int i = beginIndex;
 739         int limit = -Integer.MAX_VALUE;
 740 
 741         if (i < endIndex) {
 742             char firstChar = s.charAt(i);
 743             if (firstChar < '0') { // Possible leading "+" or "-"
 744                 if (firstChar == '-') {
 745                     negative = true;
 746                     limit = Integer.MIN_VALUE;
 747                 } else if (firstChar != '+') {
 748                     throw NumberFormatException.forCharSequence(s, beginIndex,
 749                             endIndex, i);
 750                 }
 751                 i++;
 752                 if (i == endIndex) { // Cannot have lone "+" or "-"
 753                     throw NumberFormatException.forCharSequence(s, beginIndex,
 754                             endIndex, i);
 755                 }
 756             }
 757             int multmin = limit / radix;
 758             int result = 0;
 759             while (i < endIndex) {
 760                 // Accumulating negatively avoids surprises near MAX_VALUE
 761                 int digit = Character.digit(s.charAt(i), radix);
 762                 if (digit < 0 || result < multmin) {
 763                     throw NumberFormatException.forCharSequence(s, beginIndex,
 764                             endIndex, i);
 765                 }
 766                 result *= radix;
 767                 if (result < limit + digit) {
 768                     throw NumberFormatException.forCharSequence(s, beginIndex,
 769                             endIndex, i);
 770                 }
 771                 i++;
 772                 result -= digit;
 773             }
 774             return negative ? result : -result;
 775         } else {
 776             throw NumberFormatException.forInputString("");
 777         }
 778     }
 779 
 780     /**
 781      * Parses the string argument as a signed decimal integer. The
 782      * characters in the string must all be decimal digits, except
 783      * that the first character may be an ASCII minus sign {@code '-'}
 784      * ({@code '\u005Cu002D'}) to indicate a negative value or an
 785      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
 786      * indicate a positive value. The resulting integer value is
 787      * returned, exactly as if the argument and the radix 10 were
 788      * given as arguments to the {@link #parseInt(java.lang.String,
 789      * int)} method.
 790      *
 791      * @param s    a {@code String} containing the {@code int}
 792      *             representation to be parsed
 793      * @return     the integer value represented by the argument in decimal.
 794      * @exception  NumberFormatException  if the string does not contain a
 795      *               parsable integer.
 796      */
 797     public static int parseInt(String s) throws NumberFormatException {
 798         return parseInt(s,10);
 799     }
 800 
 801     /**
 802      * Parses the string argument as an unsigned integer in the radix
 803      * specified by the second argument.  An unsigned integer maps the
 804      * values usually associated with negative numbers to positive
 805      * numbers larger than {@code MAX_VALUE}.
 806      *
 807      * The characters in the string must all be digits of the
 808      * specified radix (as determined by whether {@link
 809      * java.lang.Character#digit(char, int)} returns a nonnegative
 810      * value), except that the first character may be an ASCII plus
 811      * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
 812      * integer value is returned.
 813      *
 814      * <p>An exception of type {@code NumberFormatException} is
 815      * thrown if any of the following situations occurs:
 816      * <ul>
 817      * <li>The first argument is {@code null} or is a string of
 818      * length zero.
 819      *
 820      * <li>The radix is either smaller than
 821      * {@link java.lang.Character#MIN_RADIX} or
 822      * larger than {@link java.lang.Character#MAX_RADIX}.
 823      *
 824      * <li>Any character of the string is not a digit of the specified
 825      * radix, except that the first character may be a plus sign
 826      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 827      * string is longer than length 1.
 828      *
 829      * <li>The value represented by the string is larger than the
 830      * largest unsigned {@code int}, 2<sup>32</sup>-1.
 831      *
 832      * </ul>
 833      *
 834      *
 835      * @param      s   the {@code String} containing the unsigned integer
 836      *                  representation to be parsed
 837      * @param      radix   the radix to be used while parsing {@code s}.
 838      * @return     the integer represented by the string argument in the
 839      *             specified radix.
 840      * @throws     NumberFormatException if the {@code String}
 841      *             does not contain a parsable {@code int}.
 842      * @since 1.8
 843      */
 844     public static int parseUnsignedInt(String s, int radix)
 845                 throws NumberFormatException {
 846         if (s == null)  {
 847             throw new NumberFormatException("null");
 848         }
 849 
 850         int len = s.length();
 851         if (len > 0) {
 852             char firstChar = s.charAt(0);
 853             if (firstChar == '-') {
 854                 throw new
 855                     NumberFormatException(String.format("Illegal leading minus sign " +
 856                                                        "on unsigned string %s.", s));
 857             } else {
 858                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 859                     (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
 860                     return parseInt(s, radix);
 861                 } else {
 862                     long ell = Long.parseLong(s, radix);
 863                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 864                         return (int) ell;
 865                     } else {
 866                         throw new
 867                             NumberFormatException(String.format("String value %s exceeds " +
 868                                                                 "range of unsigned int.", s));
 869                     }
 870                 }
 871             }
 872         } else {
 873             throw NumberFormatException.forInputString(s);
 874         }
 875     }
 876 
 877     /**
 878      * Parses the {@link CharSequence} argument as an unsigned {@code int} in
 879      * the specified {@code radix}, beginning at the specified
 880      * {@code beginIndex} and extending to {@code endIndex - 1}.
 881      *
 882      * <p>The method does not take steps to guard against the
 883      * {@code CharSequence} being mutated while parsing.
 884      *
 885      * @param      s   the {@code CharSequence} containing the unsigned
 886      *                 {@code int} representation to be parsed
 887      * @param      beginIndex   the beginning index, inclusive.
 888      * @param      endIndex     the ending index, exclusive.
 889      * @param      radix   the radix to be used while parsing {@code s}.
 890      * @return     the unsigned {@code int} represented by the subsequence in
 891      *             the specified radix.
 892      * @throws     NullPointerException  if {@code s} is null.
 893      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 894      *             negative, or if {@code beginIndex} is greater than
 895      *             {@code endIndex} or if {@code endIndex} is greater than
 896      *             {@code s.length()}.
 897      * @throws     NumberFormatException  if the {@code CharSequence} does not
 898      *             contain a parsable unsigned {@code int} in the specified
 899      *             {@code radix}, or if {@code radix} is either smaller than
 900      *             {@link java.lang.Character#MIN_RADIX} or larger than
 901      *             {@link java.lang.Character#MAX_RADIX}.
 902      * @since  9
 903      */
 904     public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix)
 905                 throws NumberFormatException {
 906         s = Objects.requireNonNull(s);
 907 
 908         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 909             throw new IndexOutOfBoundsException();
 910         }
 911         int start = beginIndex, len = endIndex - beginIndex;
 912 
 913         if (len > 0) {
 914             char firstChar = s.charAt(start);
 915             if (firstChar == '-') {
 916                 throw new
 917                     NumberFormatException(String.format("Illegal leading minus sign " +
 918                                                        "on unsigned string %s.", s));
 919             } else {
 920                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 921                         (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits
 922                     return parseInt(s, start, start + len, radix);
 923                 } else {
 924                     long ell = Long.parseLong(s, start, start + len, radix);
 925                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 926                         return (int) ell;
 927                     } else {
 928                         throw new
 929                             NumberFormatException(String.format("String value %s exceeds " +
 930                                                                 "range of unsigned int.", s));
 931                     }
 932                 }
 933             }
 934         } else {
 935             throw new NumberFormatException("");
 936         }
 937     }
 938 
 939     /**
 940      * Parses the string argument as an unsigned decimal integer. The
 941      * characters in the string must all be decimal digits, except
 942      * that the first character may be an ASCII plus sign {@code
 943      * '+'} ({@code '\u005Cu002B'}). The resulting integer value
 944      * is returned, exactly as if the argument and the radix 10 were
 945      * given as arguments to the {@link
 946      * #parseUnsignedInt(java.lang.String, int)} method.
 947      *
 948      * @param s   a {@code String} containing the unsigned {@code int}
 949      *            representation to be parsed
 950      * @return    the unsigned integer value represented by the argument in decimal.
 951      * @throws    NumberFormatException  if the string does not contain a
 952      *            parsable unsigned integer.
 953      * @since 1.8
 954      */
 955     public static int parseUnsignedInt(String s) throws NumberFormatException {
 956         return parseUnsignedInt(s, 10);
 957     }
 958 
 959     /**
 960      * Returns an {@code Integer} object holding the value
 961      * extracted from the specified {@code String} when parsed
 962      * with the radix given by the second argument. The first argument
 963      * is interpreted as representing a signed integer in the radix
 964      * specified by the second argument, exactly as if the arguments
 965      * were given to the {@link #parseInt(java.lang.String, int)}
 966      * method. The result is an {@code Integer} object that
 967      * represents the integer value specified by the string.
 968      *
 969      * <p>In other words, this method returns an {@code Integer}
 970      * object equal to the value of:
 971      *
 972      * <blockquote>
 973      *  {@code new Integer(Integer.parseInt(s, radix))}
 974      * </blockquote>
 975      *
 976      * @param      s   the string to be parsed.
 977      * @param      radix the radix to be used in interpreting {@code s}
 978      * @return     an {@code Integer} object holding the value
 979      *             represented by the string argument in the specified
 980      *             radix.
 981      * @exception NumberFormatException if the {@code String}
 982      *            does not contain a parsable {@code int}.
 983      */
 984     public static Integer valueOf(String s, int radix) throws NumberFormatException {
 985         return Integer.valueOf(parseInt(s,radix));
 986     }
 987 
 988     /**
 989      * Returns an {@code Integer} object holding the
 990      * value of the specified {@code String}. The argument is
 991      * interpreted as representing a signed decimal integer, exactly
 992      * as if the argument were given to the {@link
 993      * #parseInt(java.lang.String)} method. The result is an
 994      * {@code Integer} object that represents the integer value
 995      * specified by the string.
 996      *
 997      * <p>In other words, this method returns an {@code Integer}
 998      * object equal to the value of:
 999      *
1000      * <blockquote>
1001      *  {@code new Integer(Integer.parseInt(s))}
1002      * </blockquote>
1003      *
1004      * @param      s   the string to be parsed.
1005      * @return     an {@code Integer} object holding the value
1006      *             represented by the string argument.
1007      * @exception  NumberFormatException  if the string cannot be parsed
1008      *             as an integer.
1009      */
1010     public static Integer valueOf(String s) throws NumberFormatException {
1011         return Integer.valueOf(parseInt(s, 10));
1012     }
1013 
1014     /**
1015      * Cache to support the object identity semantics of autoboxing for values between
1016      * -128 and 127 (inclusive) as required by JLS.
1017      *
1018      * The cache is initialized on first usage.  The size of the cache
1019      * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
1020      * During VM initialization, java.lang.Integer.IntegerCache.high property
1021      * may be set and saved in the private system properties in the
1022      * jdk.internal.misc.VM class.
1023      */
1024 
1025     private static class IntegerCache {
1026         static final int low = -128;
1027         static final int high;
1028         static final Integer cache[];
1029 
1030         static {
1031             // high value may be configured by property
1032             int h = 127;
1033             String integerCacheHighPropValue =
1034                 VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
1035             if (integerCacheHighPropValue != null) {
1036                 try {
1037                     int i = parseInt(integerCacheHighPropValue);
1038                     i = Math.max(i, 127);
1039                     // Maximum array size is Integer.MAX_VALUE
1040                     h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
1041                 } catch( NumberFormatException nfe) {
1042                     // If the property cannot be parsed into an int, ignore it.
1043                 }
1044             }
1045             high = h;
1046 
1047             cache = new Integer[(high - low) + 1];
1048             int j = low;
1049             for(int k = 0; k < cache.length; k++)
1050                 cache[k] = new Integer(j++);
1051 
1052             // range [-128, 127] must be interned (JLS7 5.1.7)
1053             assert IntegerCache.high >= 127;
1054         }
1055 
1056         private IntegerCache() {}
1057     }
1058 
1059     /**
1060      * Returns an {@code Integer} instance representing the specified
1061      * {@code int} value.  If a new {@code Integer} instance is not
1062      * required, this method should generally be used in preference to
1063      * the constructor {@link #Integer(int)}, as this method is likely
1064      * to yield significantly better space and time performance by
1065      * caching frequently requested values.
1066      *
1067      * This method will always cache values in the range -128 to 127,
1068      * inclusive, and may cache other values outside of this range.
1069      *
1070      * @param  i an {@code int} value.
1071      * @return an {@code Integer} instance representing {@code i}.
1072      * @since  1.5
1073      */
1074     @HotSpotIntrinsicCandidate
1075     public static Integer valueOf(int i) {
1076         if (i >= IntegerCache.low && i <= IntegerCache.high)
1077             return IntegerCache.cache[i + (-IntegerCache.low)];
1078         return new Integer(i);
1079     }
1080 
1081     /**
1082      * The value of the {@code Integer}.
1083      *
1084      * @serial
1085      */
1086     private final int value;
1087 
1088     /**
1089      * Constructs a newly allocated {@code Integer} object that
1090      * represents the specified {@code int} value.
1091      *
1092      * @param   value   the value to be represented by the
1093      *                  {@code Integer} object.
1094      */
1095     public Integer(int value) {
1096         this.value = value;
1097     }
1098 
1099     /**
1100      * Constructs a newly allocated {@code Integer} object that
1101      * represents the {@code int} value indicated by the
1102      * {@code String} parameter. The string is converted to an
1103      * {@code int} value in exactly the manner used by the
1104      * {@code parseInt} method for radix 10.
1105      *
1106      * @param      s   the {@code String} to be converted to an
1107      *                 {@code Integer}.
1108      * @exception  NumberFormatException  if the {@code String} does not
1109      *               contain a parsable integer.
1110      * @see        java.lang.Integer#parseInt(java.lang.String, int)
1111      */
1112     public Integer(String s) throws NumberFormatException {
1113         this.value = parseInt(s, 10);
1114     }
1115 
1116     /**
1117      * Returns the value of this {@code Integer} as a {@code byte}
1118      * after a narrowing primitive conversion.
1119      * @jls 5.1.3 Narrowing Primitive Conversions
1120      */
1121     public byte byteValue() {
1122         return (byte)value;
1123     }
1124 
1125     /**
1126      * Returns the value of this {@code Integer} as a {@code short}
1127      * after a narrowing primitive conversion.
1128      * @jls 5.1.3 Narrowing Primitive Conversions
1129      */
1130     public short shortValue() {
1131         return (short)value;
1132     }
1133 
1134     /**
1135      * Returns the value of this {@code Integer} as an
1136      * {@code int}.
1137      */
1138     @HotSpotIntrinsicCandidate
1139     public int intValue() {
1140         return value;
1141     }
1142 
1143     /**
1144      * Returns the value of this {@code Integer} as a {@code long}
1145      * after a widening primitive conversion.
1146      * @jls 5.1.2 Widening Primitive Conversions
1147      * @see Integer#toUnsignedLong(int)
1148      */
1149     public long longValue() {
1150         return (long)value;
1151     }
1152 
1153     /**
1154      * Returns the value of this {@code Integer} as a {@code float}
1155      * after a widening primitive conversion.
1156      * @jls 5.1.2 Widening Primitive Conversions
1157      */
1158     public float floatValue() {
1159         return (float)value;
1160     }
1161 
1162     /**
1163      * Returns the value of this {@code Integer} as a {@code double}
1164      * after a widening primitive conversion.
1165      * @jls 5.1.2 Widening Primitive Conversions
1166      */
1167     public double doubleValue() {
1168         return (double)value;
1169     }
1170 
1171     /**
1172      * Returns a {@code String} object representing this
1173      * {@code Integer}'s value. The value is converted to signed
1174      * decimal representation and returned as a string, exactly as if
1175      * the integer value were given as an argument to the {@link
1176      * java.lang.Integer#toString(int)} method.
1177      *
1178      * @return  a string representation of the value of this object in
1179      *          base&nbsp;10.
1180      */
1181     public String toString() {
1182         return toString(value);
1183     }
1184 
1185     /**
1186      * Returns a hash code for this {@code Integer}.
1187      *
1188      * @return  a hash code value for this object, equal to the
1189      *          primitive {@code int} value represented by this
1190      *          {@code Integer} object.
1191      */
1192     @Override
1193     public int hashCode() {
1194         return Integer.hashCode(value);
1195     }
1196 
1197     /**
1198      * Returns a hash code for a {@code int} value; compatible with
1199      * {@code Integer.hashCode()}.
1200      *
1201      * @param value the value to hash
1202      * @since 1.8
1203      *
1204      * @return a hash code value for a {@code int} value.
1205      */
1206     public static int hashCode(int value) {
1207         return value;
1208     }
1209 
1210     /**
1211      * Compares this object to the specified object.  The result is
1212      * {@code true} if and only if the argument is not
1213      * {@code null} and is an {@code Integer} object that
1214      * contains the same {@code int} value as this object.
1215      *
1216      * @param   obj   the object to compare with.
1217      * @return  {@code true} if the objects are the same;
1218      *          {@code false} otherwise.
1219      */
1220     public boolean equals(Object obj) {
1221         if (obj instanceof Integer) {
1222             return value == ((Integer)obj).intValue();
1223         }
1224         return false;
1225     }
1226 
1227     /**
1228      * Determines the integer value of the system property with the
1229      * specified name.
1230      *
1231      * <p>The first argument is treated as the name of a system
1232      * property.  System properties are accessible through the {@link
1233      * java.lang.System#getProperty(java.lang.String)} method. The
1234      * string value of this property is then interpreted as an integer
1235      * value using the grammar supported by {@link Integer#decode decode} and
1236      * an {@code Integer} object representing this value is returned.
1237      *
1238      * <p>If there is no property with the specified name, if the
1239      * specified name is empty or {@code null}, or if the property
1240      * does not have the correct numeric format, then {@code null} is
1241      * returned.
1242      *
1243      * <p>In other words, this method returns an {@code Integer}
1244      * object equal to the value of:
1245      *
1246      * <blockquote>
1247      *  {@code getInteger(nm, null)}
1248      * </blockquote>
1249      *
1250      * @param   nm   property name.
1251      * @return  the {@code Integer} value of the property.
1252      * @throws  SecurityException for the same reasons as
1253      *          {@link System#getProperty(String) System.getProperty}
1254      * @see     java.lang.System#getProperty(java.lang.String)
1255      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1256      */
1257     public static Integer getInteger(String nm) {
1258         return getInteger(nm, null);
1259     }
1260 
1261     /**
1262      * Determines the integer value of the system property with the
1263      * specified name.
1264      *
1265      * <p>The first argument is treated as the name of a system
1266      * property.  System properties are accessible through the {@link
1267      * java.lang.System#getProperty(java.lang.String)} method. The
1268      * string value of this property is then interpreted as an integer
1269      * value using the grammar supported by {@link Integer#decode decode} and
1270      * an {@code Integer} object representing this value is returned.
1271      *
1272      * <p>The second argument is the default value. An {@code Integer} object
1273      * that represents the value of the second argument is returned if there
1274      * is no property of the specified name, if the property does not have
1275      * the correct numeric format, or if the specified name is empty or
1276      * {@code null}.
1277      *
1278      * <p>In other words, this method returns an {@code Integer} object
1279      * equal to the value of:
1280      *
1281      * <blockquote>
1282      *  {@code getInteger(nm, new Integer(val))}
1283      * </blockquote>
1284      *
1285      * but in practice it may be implemented in a manner such as:
1286      *
1287      * <blockquote><pre>
1288      * Integer result = getInteger(nm, null);
1289      * return (result == null) ? new Integer(val) : result;
1290      * </pre></blockquote>
1291      *
1292      * to avoid the unnecessary allocation of an {@code Integer}
1293      * object when the default value is not needed.
1294      *
1295      * @param   nm   property name.
1296      * @param   val   default value.
1297      * @return  the {@code Integer} value of the property.
1298      * @throws  SecurityException for the same reasons as
1299      *          {@link System#getProperty(String) System.getProperty}
1300      * @see     java.lang.System#getProperty(java.lang.String)
1301      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1302      */
1303     public static Integer getInteger(String nm, int val) {
1304         Integer result = getInteger(nm, null);
1305         return (result == null) ? Integer.valueOf(val) : result;
1306     }
1307 
1308     /**
1309      * Returns the integer value of the system property with the
1310      * specified name.  The first argument is treated as the name of a
1311      * system property.  System properties are accessible through the
1312      * {@link java.lang.System#getProperty(java.lang.String)} method.
1313      * The string value of this property is then interpreted as an
1314      * integer value, as per the {@link Integer#decode decode} method,
1315      * and an {@code Integer} object representing this value is
1316      * returned; in summary:
1317      *
1318      * <ul><li>If the property value begins with the two ASCII characters
1319      *         {@code 0x} or the ASCII character {@code #}, not
1320      *      followed by a minus sign, then the rest of it is parsed as a
1321      *      hexadecimal integer exactly as by the method
1322      *      {@link #valueOf(java.lang.String, int)} with radix 16.
1323      * <li>If the property value begins with the ASCII character
1324      *     {@code 0} followed by another character, it is parsed as an
1325      *     octal integer exactly as by the method
1326      *     {@link #valueOf(java.lang.String, int)} with radix 8.
1327      * <li>Otherwise, the property value is parsed as a decimal integer
1328      * exactly as by the method {@link #valueOf(java.lang.String, int)}
1329      * with radix 10.
1330      * </ul>
1331      *
1332      * <p>The second argument is the default value. The default value is
1333      * returned if there is no property of the specified name, if the
1334      * property does not have the correct numeric format, or if the
1335      * specified name is empty or {@code null}.
1336      *
1337      * @param   nm   property name.
1338      * @param   val   default value.
1339      * @return  the {@code Integer} value of the property.
1340      * @throws  SecurityException for the same reasons as
1341      *          {@link System#getProperty(String) System.getProperty}
1342      * @see     System#getProperty(java.lang.String)
1343      * @see     System#getProperty(java.lang.String, java.lang.String)
1344      */
1345     public static Integer getInteger(String nm, Integer val) {
1346         String v = null;
1347         try {
1348             v = System.getProperty(nm);
1349         } catch (IllegalArgumentException | NullPointerException e) {
1350         }
1351         if (v != null) {
1352             try {
1353                 return Integer.decode(v);
1354             } catch (NumberFormatException e) {
1355             }
1356         }
1357         return val;
1358     }
1359 
1360     /**
1361      * Decodes a {@code String} into an {@code Integer}.
1362      * Accepts decimal, hexadecimal, and octal numbers given
1363      * by the following grammar:
1364      *
1365      * <blockquote>
1366      * <dl>
1367      * <dt><i>DecodableString:</i>
1368      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1369      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1370      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1371      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1372      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1373      *
1374      * <dt><i>Sign:</i>
1375      * <dd>{@code -}
1376      * <dd>{@code +}
1377      * </dl>
1378      * </blockquote>
1379      *
1380      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1381      * are as defined in section 3.10.1 of
1382      * <cite>The Java&trade; Language Specification</cite>,
1383      * except that underscores are not accepted between digits.
1384      *
1385      * <p>The sequence of characters following an optional
1386      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1387      * "{@code #}", or leading zero) is parsed as by the {@code
1388      * Integer.parseInt} method with the indicated radix (10, 16, or
1389      * 8).  This sequence of characters must represent a positive
1390      * value or a {@link NumberFormatException} will be thrown.  The
1391      * result is negated if first character of the specified {@code
1392      * String} is the minus sign.  No whitespace characters are
1393      * permitted in the {@code String}.
1394      *
1395      * @param     nm the {@code String} to decode.
1396      * @return    an {@code Integer} object holding the {@code int}
1397      *             value represented by {@code nm}
1398      * @exception NumberFormatException  if the {@code String} does not
1399      *            contain a parsable integer.
1400      * @see java.lang.Integer#parseInt(java.lang.String, int)
1401      */
1402     public static Integer decode(String nm) throws NumberFormatException {
1403         int radix = 10;
1404         int index = 0;
1405         boolean negative = false;
1406         Integer result;
1407 
1408         if (nm.length() == 0)
1409             throw new NumberFormatException("Zero length string");
1410         char firstChar = nm.charAt(0);
1411         // Handle sign, if present
1412         if (firstChar == '-') {
1413             negative = true;
1414             index++;
1415         } else if (firstChar == '+')
1416             index++;
1417 
1418         // Handle radix specifier, if present
1419         if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1420             index += 2;
1421             radix = 16;
1422         }
1423         else if (nm.startsWith("#", index)) {
1424             index ++;
1425             radix = 16;
1426         }
1427         else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1428             index ++;
1429             radix = 8;
1430         }
1431 
1432         if (nm.startsWith("-", index) || nm.startsWith("+", index))
1433             throw new NumberFormatException("Sign character in wrong position");
1434 
1435         try {
1436             result = Integer.valueOf(nm.substring(index), radix);
1437             result = negative ? Integer.valueOf(-result.intValue()) : result;
1438         } catch (NumberFormatException e) {
1439             // If number is Integer.MIN_VALUE, we'll end up here. The next line
1440             // handles this case, and causes any genuine format error to be
1441             // rethrown.
1442             String constant = negative ? ("-" + nm.substring(index))
1443                                        : nm.substring(index);
1444             result = Integer.valueOf(constant, radix);
1445         }
1446         return result;
1447     }
1448 
1449     /**
1450      * Compares two {@code Integer} objects numerically.
1451      *
1452      * @param   anotherInteger   the {@code Integer} to be compared.
1453      * @return  the value {@code 0} if this {@code Integer} is
1454      *          equal to the argument {@code Integer}; a value less than
1455      *          {@code 0} if this {@code Integer} is numerically less
1456      *          than the argument {@code Integer}; and a value greater
1457      *          than {@code 0} if this {@code Integer} is numerically
1458      *           greater than the argument {@code Integer} (signed
1459      *           comparison).
1460      * @since   1.2
1461      */
1462     public int compareTo(Integer anotherInteger) {
1463         return compare(this.value, anotherInteger.value);
1464     }
1465 
1466     /**
1467      * Compares two {@code int} values numerically.
1468      * The value returned is identical to what would be returned by:
1469      * <pre>
1470      *    Integer.valueOf(x).compareTo(Integer.valueOf(y))
1471      * </pre>
1472      *
1473      * @param  x the first {@code int} to compare
1474      * @param  y the second {@code int} to compare
1475      * @return the value {@code 0} if {@code x == y};
1476      *         a value less than {@code 0} if {@code x < y}; and
1477      *         a value greater than {@code 0} if {@code x > y}
1478      * @since 1.7
1479      */
1480     public static int compare(int x, int y) {
1481         return (x < y) ? -1 : ((x == y) ? 0 : 1);
1482     }
1483 
1484     /**
1485      * Compares two {@code int} values numerically treating the values
1486      * as unsigned.
1487      *
1488      * @param  x the first {@code int} to compare
1489      * @param  y the second {@code int} to compare
1490      * @return the value {@code 0} if {@code x == y}; a value less
1491      *         than {@code 0} if {@code x < y} as unsigned values; and
1492      *         a value greater than {@code 0} if {@code x > y} as
1493      *         unsigned values
1494      * @since 1.8
1495      */
1496     public static int compareUnsigned(int x, int y) {
1497         return compare(x + MIN_VALUE, y + MIN_VALUE);
1498     }
1499 
1500     /**
1501      * Converts the argument to a {@code long} by an unsigned
1502      * conversion.  In an unsigned conversion to a {@code long}, the
1503      * high-order 32 bits of the {@code long} are zero and the
1504      * low-order 32 bits are equal to the bits of the integer
1505      * argument.
1506      *
1507      * Consequently, zero and positive {@code int} values are mapped
1508      * to a numerically equal {@code long} value and negative {@code
1509      * int} values are mapped to a {@code long} value equal to the
1510      * input plus 2<sup>32</sup>.
1511      *
1512      * @param  x the value to convert to an unsigned {@code long}
1513      * @return the argument converted to {@code long} by an unsigned
1514      *         conversion
1515      * @since 1.8
1516      */
1517     public static long toUnsignedLong(int x) {
1518         return ((long) x) & 0xffffffffL;
1519     }
1520 
1521     /**
1522      * Returns the unsigned quotient of dividing the first argument by
1523      * the second where each argument and the result is interpreted as
1524      * an unsigned value.
1525      *
1526      * <p>Note that in two's complement arithmetic, the three other
1527      * basic arithmetic operations of add, subtract, and multiply are
1528      * bit-wise identical if the two operands are regarded as both
1529      * being signed or both being unsigned.  Therefore separate {@code
1530      * addUnsigned}, etc. methods are not provided.
1531      *
1532      * @param dividend the value to be divided
1533      * @param divisor the value doing the dividing
1534      * @return the unsigned quotient of the first argument divided by
1535      * the second argument
1536      * @see #remainderUnsigned
1537      * @since 1.8
1538      */
1539     public static int divideUnsigned(int dividend, int divisor) {
1540         // In lieu of tricky code, for now just use long arithmetic.
1541         return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1542     }
1543 
1544     /**
1545      * Returns the unsigned remainder from dividing the first argument
1546      * by the second where each argument and the result is interpreted
1547      * as an unsigned value.
1548      *
1549      * @param dividend the value to be divided
1550      * @param divisor the value doing the dividing
1551      * @return the unsigned remainder of the first argument divided by
1552      * the second argument
1553      * @see #divideUnsigned
1554      * @since 1.8
1555      */
1556     public static int remainderUnsigned(int dividend, int divisor) {
1557         // In lieu of tricky code, for now just use long arithmetic.
1558         return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1559     }
1560 
1561 
1562     // Bit twiddling
1563 
1564     /**
1565      * The number of bits used to represent an {@code int} value in two's
1566      * complement binary form.
1567      *
1568      * @since 1.5
1569      */
1570     @Native public static final int SIZE = 32;
1571 
1572     /**
1573      * The number of bytes used to represent a {@code int} value in two's
1574      * complement binary form.
1575      *
1576      * @since 1.8
1577      */
1578     public static final int BYTES = SIZE / Byte.SIZE;
1579 
1580     /**
1581      * Returns an {@code int} value with at most a single one-bit, in the
1582      * position of the highest-order ("leftmost") one-bit in the specified
1583      * {@code int} value.  Returns zero if the specified value has no
1584      * one-bits in its two's complement binary representation, that is, if it
1585      * is equal to zero.
1586      *
1587      * @param i the value whose highest one bit is to be computed
1588      * @return an {@code int} value with a single one-bit, in the position
1589      *     of the highest-order one-bit in the specified value, or zero if
1590      *     the specified value is itself equal to zero.
1591      * @since 1.5
1592      */
1593     public static int highestOneBit(int i) {
1594         // HD, Figure 3-1
1595         i |= (i >>  1);
1596         i |= (i >>  2);
1597         i |= (i >>  4);
1598         i |= (i >>  8);
1599         i |= (i >> 16);
1600         return i - (i >>> 1);
1601     }
1602 
1603     /**
1604      * Returns an {@code int} value with at most a single one-bit, in the
1605      * position of the lowest-order ("rightmost") one-bit in the specified
1606      * {@code int} value.  Returns zero if the specified value has no
1607      * one-bits in its two's complement binary representation, that is, if it
1608      * is equal to zero.
1609      *
1610      * @param i the value whose lowest one bit is to be computed
1611      * @return an {@code int} value with a single one-bit, in the position
1612      *     of the lowest-order one-bit in the specified value, or zero if
1613      *     the specified value is itself equal to zero.
1614      * @since 1.5
1615      */
1616     public static int lowestOneBit(int i) {
1617         // HD, Section 2-1
1618         return i & -i;
1619     }
1620 
1621     /**
1622      * Returns the number of zero bits preceding the highest-order
1623      * ("leftmost") one-bit in the two's complement binary representation
1624      * of the specified {@code int} value.  Returns 32 if the
1625      * specified value has no one-bits in its two's complement representation,
1626      * in other words if it is equal to zero.
1627      *
1628      * <p>Note that this method is closely related to the logarithm base 2.
1629      * For all positive {@code int} values x:
1630      * <ul>
1631      * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1632      * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1633      * </ul>
1634      *
1635      * @param i the value whose number of leading zeros is to be computed
1636      * @return the number of zero bits preceding the highest-order
1637      *     ("leftmost") one-bit in the two's complement binary representation
1638      *     of the specified {@code int} value, or 32 if the value
1639      *     is equal to zero.
1640      * @since 1.5
1641      */
1642     @HotSpotIntrinsicCandidate
1643     public static int numberOfLeadingZeros(int i) {
1644         // HD, Figure 5-6
1645         if (i == 0)
1646             return 32;
1647         int n = 1;
1648         if (i >>> 16 == 0) { n += 16; i <<= 16; }
1649         if (i >>> 24 == 0) { n +=  8; i <<=  8; }
1650         if (i >>> 28 == 0) { n +=  4; i <<=  4; }
1651         if (i >>> 30 == 0) { n +=  2; i <<=  2; }
1652         n -= i >>> 31;
1653         return n;
1654     }
1655 
1656     /**
1657      * Returns the number of zero bits following the lowest-order ("rightmost")
1658      * one-bit in the two's complement binary representation of the specified
1659      * {@code int} value.  Returns 32 if the specified value has no
1660      * one-bits in its two's complement representation, in other words if it is
1661      * equal to zero.
1662      *
1663      * @param i the value whose number of trailing zeros is to be computed
1664      * @return the number of zero bits following the lowest-order ("rightmost")
1665      *     one-bit in the two's complement binary representation of the
1666      *     specified {@code int} value, or 32 if the value is equal
1667      *     to zero.
1668      * @since 1.5
1669      */
1670     @HotSpotIntrinsicCandidate
1671     public static int numberOfTrailingZeros(int i) {
1672         // HD, Figure 5-14
1673         int y;
1674         if (i == 0) return 32;
1675         int n = 31;
1676         y = i <<16; if (y != 0) { n = n -16; i = y; }
1677         y = i << 8; if (y != 0) { n = n - 8; i = y; }
1678         y = i << 4; if (y != 0) { n = n - 4; i = y; }
1679         y = i << 2; if (y != 0) { n = n - 2; i = y; }
1680         return n - ((i << 1) >>> 31);
1681     }
1682 
1683     /**
1684      * Returns the number of one-bits in the two's complement binary
1685      * representation of the specified {@code int} value.  This function is
1686      * sometimes referred to as the <i>population count</i>.
1687      *
1688      * @param i the value whose bits are to be counted
1689      * @return the number of one-bits in the two's complement binary
1690      *     representation of the specified {@code int} value.
1691      * @since 1.5
1692      */
1693     @HotSpotIntrinsicCandidate
1694     public static int bitCount(int i) {
1695         // HD, Figure 5-2
1696         i = i - ((i >>> 1) & 0x55555555);
1697         i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1698         i = (i + (i >>> 4)) & 0x0f0f0f0f;
1699         i = i + (i >>> 8);
1700         i = i + (i >>> 16);
1701         return i & 0x3f;
1702     }
1703 
1704     /**
1705      * Returns the value obtained by rotating the two's complement binary
1706      * representation of the specified {@code int} value left by the
1707      * specified number of bits.  (Bits shifted out of the left hand, or
1708      * high-order, side reenter on the right, or low-order.)
1709      *
1710      * <p>Note that left rotation with a negative distance is equivalent to
1711      * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1712      * distance)}.  Note also that rotation by any multiple of 32 is a
1713      * no-op, so all but the last five bits of the rotation distance can be
1714      * ignored, even if the distance is negative: {@code rotateLeft(val,
1715      * distance) == rotateLeft(val, distance & 0x1F)}.
1716      *
1717      * @param i the value whose bits are to be rotated left
1718      * @param distance the number of bit positions to rotate left
1719      * @return the value obtained by rotating the two's complement binary
1720      *     representation of the specified {@code int} value left by the
1721      *     specified number of bits.
1722      * @since 1.5
1723      */
1724     public static int rotateLeft(int i, int distance) {
1725         return (i << distance) | (i >>> -distance);
1726     }
1727 
1728     /**
1729      * Returns the value obtained by rotating the two's complement binary
1730      * representation of the specified {@code int} value right by the
1731      * specified number of bits.  (Bits shifted out of the right hand, or
1732      * low-order, side reenter on the left, or high-order.)
1733      *
1734      * <p>Note that right rotation with a negative distance is equivalent to
1735      * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1736      * distance)}.  Note also that rotation by any multiple of 32 is a
1737      * no-op, so all but the last five bits of the rotation distance can be
1738      * ignored, even if the distance is negative: {@code rotateRight(val,
1739      * distance) == rotateRight(val, distance & 0x1F)}.
1740      *
1741      * @param i the value whose bits are to be rotated right
1742      * @param distance the number of bit positions to rotate right
1743      * @return the value obtained by rotating the two's complement binary
1744      *     representation of the specified {@code int} value right by the
1745      *     specified number of bits.
1746      * @since 1.5
1747      */
1748     public static int rotateRight(int i, int distance) {
1749         return (i >>> distance) | (i << -distance);
1750     }
1751 
1752     /**
1753      * Returns the value obtained by reversing the order of the bits in the
1754      * two's complement binary representation of the specified {@code int}
1755      * value.
1756      *
1757      * @param i the value to be reversed
1758      * @return the value obtained by reversing order of the bits in the
1759      *     specified {@code int} value.
1760      * @since 1.5
1761      */
1762     public static int reverse(int i) {
1763         // HD, Figure 7-1
1764         i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1765         i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1766         i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1767         i = (i << 24) | ((i & 0xff00) << 8) |
1768             ((i >>> 8) & 0xff00) | (i >>> 24);
1769         return i;
1770     }
1771 
1772     /**
1773      * Returns the signum function of the specified {@code int} value.  (The
1774      * return value is -1 if the specified value is negative; 0 if the
1775      * specified value is zero; and 1 if the specified value is positive.)
1776      *
1777      * @param i the value whose signum is to be computed
1778      * @return the signum function of the specified {@code int} value.
1779      * @since 1.5
1780      */
1781     public static int signum(int i) {
1782         // HD, Section 2-7
1783         return (i >> 31) | (-i >>> 31);
1784     }
1785 
1786     /**
1787      * Returns the value obtained by reversing the order of the bytes in the
1788      * two's complement representation of the specified {@code int} value.
1789      *
1790      * @param i the value whose bytes are to be reversed
1791      * @return the value obtained by reversing the bytes in the specified
1792      *     {@code int} value.
1793      * @since 1.5
1794      */
1795     @HotSpotIntrinsicCandidate
1796     public static int reverseBytes(int i) {
1797         return ((i >>> 24)           ) |
1798                ((i >>   8) &   0xFF00) |
1799                ((i <<   8) & 0xFF0000) |
1800                ((i << 24));
1801     }
1802 
1803     /**
1804      * Adds two integers together as per the + operator.
1805      *
1806      * @param a the first operand
1807      * @param b the second operand
1808      * @return the sum of {@code a} and {@code b}
1809      * @see java.util.function.BinaryOperator
1810      * @since 1.8
1811      */
1812     public static int sum(int a, int b) {
1813         return a + b;
1814     }
1815 
1816     /**
1817      * Returns the greater of two {@code int} values
1818      * as if by calling {@link Math#max(int, int) Math.max}.
1819      *
1820      * @param a the first operand
1821      * @param b the second operand
1822      * @return the greater of {@code a} and {@code b}
1823      * @see java.util.function.BinaryOperator
1824      * @since 1.8
1825      */
1826     public static int max(int a, int b) {
1827         return Math.max(a, b);
1828     }
1829 
1830     /**
1831      * Returns the smaller of two {@code int} values
1832      * as if by calling {@link Math#min(int, int) Math.min}.
1833      *
1834      * @param a the first operand
1835      * @param b the second operand
1836      * @return the smaller of {@code a} and {@code b}
1837      * @see java.util.function.BinaryOperator
1838      * @since 1.8
1839      */
1840     public static int min(int a, int b) {
1841         return Math.min(a, b);
1842     }
1843 
1844     /** use serialVersionUID from JDK 1.0.2 for interoperability */
1845     @Native private static final long serialVersionUID = 1360826667806852920L;
1846 }
--- EOF ---