1 /*
   2  * Copyright (c) 1994, 2018, 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         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     private 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 byte[] 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 byte[] 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 
 426     /**
 427      * Returns a {@code String} object representing the
 428      * specified integer. The argument is converted to signed decimal
 429      * representation and returned as a string, exactly as if the
 430      * argument and radix 10 were given as arguments to the {@link
 431      * #toString(int, int)} method.
 432      *
 433      * @param   i   an integer to be converted.
 434      * @return  a string representation of the argument in base&nbsp;10.
 435      */
 436     @HotSpotIntrinsicCandidate
 437     public static String toString(int i) {
 438         int size = stringSize(i);
 439         if (COMPACT_STRINGS) {
 440             byte[] buf = new byte[size];
 441             getChars(i, size, buf);
 442             return new String(buf, LATIN1);
 443         } else {
 444             byte[] buf = new byte[size * 2];
 445             StringUTF16.getChars(i, size, buf);
 446             return new String(buf, UTF16);
 447         }
 448     }
 449 
 450     /**
 451      * Returns a string representation of the argument as an unsigned
 452      * decimal value.
 453      *
 454      * The argument is converted to unsigned decimal representation
 455      * and returned as a string exactly as if the argument and radix
 456      * 10 were given as arguments to the {@link #toUnsignedString(int,
 457      * int)} method.
 458      *
 459      * @param   i  an integer to be converted to an unsigned string.
 460      * @return  an unsigned string representation of the argument.
 461      * @see     #toUnsignedString(int, int)
 462      * @since 1.8
 463      */
 464     public static String toUnsignedString(int i) {
 465         return Long.toString(toUnsignedLong(i));
 466     }
 467 
 468     /**
 469      * Places characters representing the integer i into the
 470      * character array buf. The characters are placed into
 471      * the buffer backwards starting with the least significant
 472      * digit at the specified index (exclusive), and working
 473      * backwards from there.
 474      *
 475      * @implNote This method converts positive inputs into negative
 476      * values, to cover the Integer.MIN_VALUE case. Converting otherwise
 477      * (negative to positive) will expose -Integer.MIN_VALUE that overflows
 478      * integer.
 479      *
 480      * @param i     value to convert
 481      * @param index next index, after the least significant digit
 482      * @param buf   target buffer, Latin1-encoded
 483      * @return index of the most significant digit or minus sign, if present
 484      */
 485     static int getChars(int i, int index, byte[] buf) {
 486         int q, r;
 487         int charPos = index;
 488 
 489         boolean negative = i < 0;
 490         if (!negative) {
 491             i = -i;
 492         }
 493 
 494         // Generate two digits per iteration
 495         while (i <= -100) {
 496             q = i / 100;
 497             r = (q * 100) - i;
 498             i = q;
 499             buf[--charPos] = DigitOnes[r];
 500             buf[--charPos] = DigitTens[r];
 501         }
 502 
 503         // We know there are at most two digits left at this point.
 504         q = i / 10;
 505         r = (q * 10) - i;
 506         buf[--charPos] = (byte)('0' + r);
 507 
 508         // Whatever left is the remaining digit.
 509         if (q < 0) {
 510             buf[--charPos] = (byte)('0' - q);
 511         }
 512 
 513         if (negative) {
 514             buf[--charPos] = (byte)'-';
 515         }
 516         return charPos;
 517     }
 518 
 519     // Left here for compatibility reasons, see JDK-8143900.
 520     static final int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
 521                                       99999999, 999999999, Integer.MAX_VALUE };
 522 
 523     /**
 524      * Returns the string representation size for a given int value.
 525      *
 526      * @param x int value
 527      * @return string size
 528      *
 529      * @implNote There are other ways to compute this: e.g. binary search,
 530      * but values are biased heavily towards zero, and therefore linear search
 531      * wins. The iteration results are also routinely inlined in the generated
 532      * code after loop unrolling.
 533      */
 534     static int stringSize(int x) {
 535         int d = 1;
 536         if (x >= 0) {
 537             d = 0;
 538             x = -x;
 539         }
 540         int p = -10;
 541         for (int i = 1; i < 10; i++) {
 542             if (x > p)
 543                 return i + d;
 544             p = 10 * p;
 545         }
 546         return 10 + d;
 547     }
 548 
 549     /**
 550      * Parses the string argument as a signed integer in the radix
 551      * specified by the second argument. The characters in the string
 552      * must all be digits of the specified radix (as determined by
 553      * whether {@link java.lang.Character#digit(char, int)} returns a
 554      * nonnegative value), except that the first character may be an
 555      * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
 556      * indicate a negative value or an ASCII plus sign {@code '+'}
 557      * ({@code '\u005Cu002B'}) to indicate a positive value. The
 558      * resulting integer value is returned.
 559      *
 560      * <p>An exception of type {@code NumberFormatException} is
 561      * thrown if any of the following situations occurs:
 562      * <ul>
 563      * <li>The first argument is {@code null} or is a string of
 564      * length zero.
 565      *
 566      * <li>The radix is either smaller than
 567      * {@link java.lang.Character#MIN_RADIX} or
 568      * larger than {@link java.lang.Character#MAX_RADIX}.
 569      *
 570      * <li>Any character of the string is not a digit of the specified
 571      * radix, except that the first character may be a minus sign
 572      * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
 573      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 574      * string is longer than length 1.
 575      *
 576      * <li>The value represented by the string is not a value of type
 577      * {@code int}.
 578      * </ul>
 579      *
 580      * <p>Examples:
 581      * <blockquote><pre>
 582      * parseInt("0", 10) returns 0
 583      * parseInt("473", 10) returns 473
 584      * parseInt("+42", 10) returns 42
 585      * parseInt("-0", 10) returns 0
 586      * parseInt("-FF", 16) returns -255
 587      * parseInt("1100110", 2) returns 102
 588      * parseInt("2147483647", 10) returns 2147483647
 589      * parseInt("-2147483648", 10) returns -2147483648
 590      * parseInt("2147483648", 10) throws a NumberFormatException
 591      * parseInt("99", 8) throws a NumberFormatException
 592      * parseInt("Kona", 10) throws a NumberFormatException
 593      * parseInt("Kona", 27) returns 411787
 594      * </pre></blockquote>
 595      *
 596      * @param      s   the {@code String} containing the integer
 597      *                  representation to be parsed
 598      * @param      radix   the radix to be used while parsing {@code s}.
 599      * @return     the integer represented by the string argument in the
 600      *             specified radix.
 601      * @exception  NumberFormatException if the {@code String}
 602      *             does not contain a parsable {@code int}.
 603      */
 604     public static int parseInt(String s, int radix)
 605                 throws NumberFormatException
 606     {
 607         /*
 608          * WARNING: This method may be invoked early during VM initialization
 609          * before IntegerCache is initialized. Care must be taken to not use
 610          * the valueOf method.
 611          */
 612 
 613         if (s == null) {
 614             throw new NumberFormatException("null");
 615         }
 616 
 617         if (radix < Character.MIN_RADIX) {
 618             throw new NumberFormatException("radix " + radix +
 619                                             " less than Character.MIN_RADIX");
 620         }
 621 
 622         if (radix > Character.MAX_RADIX) {
 623             throw new NumberFormatException("radix " + radix +
 624                                             " greater than Character.MAX_RADIX");
 625         }
 626 
 627         boolean negative = false;
 628         int i = 0, len = s.length();
 629         int limit = -Integer.MAX_VALUE;
 630 
 631         if (len > 0) {
 632             char firstChar = s.charAt(0);
 633             if (firstChar < '0') { // Possible leading "+" or "-"
 634                 if (firstChar == '-') {
 635                     negative = true;
 636                     limit = Integer.MIN_VALUE;
 637                 } else if (firstChar != '+') {
 638                     throw NumberFormatException.forInputString(s, radix);
 639                 }
 640 
 641                 if (len == 1) { // Cannot have lone "+" or "-"
 642                     throw NumberFormatException.forInputString(s, radix);
 643                 }
 644                 i++;
 645             }
 646             int multmin = limit / radix;
 647             int result = 0;
 648             while (i < len) {
 649                 // Accumulating negatively avoids surprises near MAX_VALUE
 650                 int digit = Character.digit(s.charAt(i++), radix);
 651                 if (digit < 0 || result < multmin) {
 652                     throw NumberFormatException.forInputString(s, radix);
 653                 }
 654                 result *= radix;
 655                 if (result < limit + digit) {
 656                     throw NumberFormatException.forInputString(s, radix);
 657                 }
 658                 result -= digit;
 659             }
 660             return negative ? result : -result;
 661         } else {
 662             throw NumberFormatException.forInputString(s, radix);
 663         }
 664     }
 665 
 666     /**
 667      * Parses the {@link CharSequence} argument as a signed {@code int} in the
 668      * specified {@code radix}, beginning at the specified {@code beginIndex}
 669      * and extending to {@code endIndex - 1}.
 670      *
 671      * <p>The method does not take steps to guard against the
 672      * {@code CharSequence} being mutated while parsing.
 673      *
 674      * @param      s   the {@code CharSequence} containing the {@code int}
 675      *                  representation to be parsed
 676      * @param      beginIndex   the beginning index, inclusive.
 677      * @param      endIndex     the ending index, exclusive.
 678      * @param      radix   the radix to be used while parsing {@code s}.
 679      * @return     the signed {@code int} represented by the subsequence in
 680      *             the specified radix.
 681      * @throws     NullPointerException  if {@code s} is null.
 682      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 683      *             negative, or if {@code beginIndex} is greater than
 684      *             {@code endIndex} or if {@code endIndex} is greater than
 685      *             {@code s.length()}.
 686      * @throws     NumberFormatException  if the {@code CharSequence} does not
 687      *             contain a parsable {@code int} in the specified
 688      *             {@code radix}, or if {@code radix} is either smaller than
 689      *             {@link java.lang.Character#MIN_RADIX} or larger than
 690      *             {@link java.lang.Character#MAX_RADIX}.
 691      * @since  9
 692      */
 693     public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix)
 694                 throws NumberFormatException {
 695         s = Objects.requireNonNull(s);
 696 
 697         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 698             throw new IndexOutOfBoundsException();
 699         }
 700         if (radix < Character.MIN_RADIX) {
 701             throw new NumberFormatException("radix " + radix +
 702                                             " less than Character.MIN_RADIX");
 703         }
 704         if (radix > Character.MAX_RADIX) {
 705             throw new NumberFormatException("radix " + radix +
 706                                             " greater than Character.MAX_RADIX");
 707         }
 708 
 709         boolean negative = false;
 710         int i = beginIndex;
 711         int limit = -Integer.MAX_VALUE;
 712 
 713         if (i < endIndex) {
 714             char firstChar = s.charAt(i);
 715             if (firstChar < '0') { // Possible leading "+" or "-"
 716                 if (firstChar == '-') {
 717                     negative = true;
 718                     limit = Integer.MIN_VALUE;
 719                 } else if (firstChar != '+') {
 720                     throw NumberFormatException.forCharSequence(s, beginIndex,
 721                             endIndex, i);
 722                 }
 723                 i++;
 724                 if (i == endIndex) { // Cannot have lone "+" or "-"
 725                     throw NumberFormatException.forCharSequence(s, beginIndex,
 726                             endIndex, i);
 727                 }
 728             }
 729             int multmin = limit / radix;
 730             int result = 0;
 731             while (i < endIndex) {
 732                 // Accumulating negatively avoids surprises near MAX_VALUE
 733                 int digit = Character.digit(s.charAt(i), radix);
 734                 if (digit < 0 || result < multmin) {
 735                     throw NumberFormatException.forCharSequence(s, beginIndex,
 736                             endIndex, i);
 737                 }
 738                 result *= radix;
 739                 if (result < limit + digit) {
 740                     throw NumberFormatException.forCharSequence(s, beginIndex,
 741                             endIndex, i);
 742                 }
 743                 i++;
 744                 result -= digit;
 745             }
 746             return negative ? result : -result;
 747         } else {
 748             throw NumberFormatException.forInputString("", radix);
 749         }
 750     }
 751 
 752     /**
 753      * Parses the string argument as a signed decimal integer. The
 754      * characters in the string must all be decimal digits, except
 755      * that the first character may be an ASCII minus sign {@code '-'}
 756      * ({@code '\u005Cu002D'}) to indicate a negative value or an
 757      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
 758      * indicate a positive value. The resulting integer value is
 759      * returned, exactly as if the argument and the radix 10 were
 760      * given as arguments to the {@link #parseInt(java.lang.String,
 761      * int)} method.
 762      *
 763      * @param s    a {@code String} containing the {@code int}
 764      *             representation to be parsed
 765      * @return     the integer value represented by the argument in decimal.
 766      * @exception  NumberFormatException  if the string does not contain a
 767      *               parsable integer.
 768      */
 769     public static int parseInt(String s) throws NumberFormatException {
 770         return parseInt(s,10);
 771     }
 772 
 773     /**
 774      * Parses the string argument as an unsigned integer in the radix
 775      * specified by the second argument.  An unsigned integer maps the
 776      * values usually associated with negative numbers to positive
 777      * numbers larger than {@code MAX_VALUE}.
 778      *
 779      * The characters in the string must all be digits of the
 780      * specified radix (as determined by whether {@link
 781      * java.lang.Character#digit(char, int)} returns a nonnegative
 782      * value), except that the first character may be an ASCII plus
 783      * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
 784      * integer value is returned.
 785      *
 786      * <p>An exception of type {@code NumberFormatException} is
 787      * thrown if any of the following situations occurs:
 788      * <ul>
 789      * <li>The first argument is {@code null} or is a string of
 790      * length zero.
 791      *
 792      * <li>The radix is either smaller than
 793      * {@link java.lang.Character#MIN_RADIX} or
 794      * larger than {@link java.lang.Character#MAX_RADIX}.
 795      *
 796      * <li>Any character of the string is not a digit of the specified
 797      * radix, except that the first character may be a plus sign
 798      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
 799      * string is longer than length 1.
 800      *
 801      * <li>The value represented by the string is larger than the
 802      * largest unsigned {@code int}, 2<sup>32</sup>-1.
 803      *
 804      * </ul>
 805      *
 806      *
 807      * @param      s   the {@code String} containing the unsigned integer
 808      *                  representation to be parsed
 809      * @param      radix   the radix to be used while parsing {@code s}.
 810      * @return     the integer represented by the string argument in the
 811      *             specified radix.
 812      * @throws     NumberFormatException if the {@code String}
 813      *             does not contain a parsable {@code int}.
 814      * @since 1.8
 815      */
 816     public static int parseUnsignedInt(String s, int radix)
 817                 throws NumberFormatException {
 818         if (s == null)  {
 819             throw new NumberFormatException("null");
 820         }
 821 
 822         int len = s.length();
 823         if (len > 0) {
 824             char firstChar = s.charAt(0);
 825             if (firstChar == '-') {
 826                 throw new
 827                     NumberFormatException(String.format("Illegal leading minus sign " +
 828                                                        "on unsigned string %s.", s));
 829             } else {
 830                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 831                     (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
 832                     return parseInt(s, radix);
 833                 } else {
 834                     long ell = Long.parseLong(s, radix);
 835                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 836                         return (int) ell;
 837                     } else {
 838                         throw new
 839                             NumberFormatException(String.format("String value %s exceeds " +
 840                                                                 "range of unsigned int.", s));
 841                     }
 842                 }
 843             }
 844         } else {
 845             throw NumberFormatException.forInputString(s, radix);
 846         }
 847     }
 848 
 849     /**
 850      * Parses the {@link CharSequence} argument as an unsigned {@code int} in
 851      * the specified {@code radix}, beginning at the specified
 852      * {@code beginIndex} and extending to {@code endIndex - 1}.
 853      *
 854      * <p>The method does not take steps to guard against the
 855      * {@code CharSequence} being mutated while parsing.
 856      *
 857      * @param      s   the {@code CharSequence} containing the unsigned
 858      *                 {@code int} representation to be parsed
 859      * @param      beginIndex   the beginning index, inclusive.
 860      * @param      endIndex     the ending index, exclusive.
 861      * @param      radix   the radix to be used while parsing {@code s}.
 862      * @return     the unsigned {@code int} represented by the subsequence in
 863      *             the specified radix.
 864      * @throws     NullPointerException  if {@code s} is null.
 865      * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
 866      *             negative, or if {@code beginIndex} is greater than
 867      *             {@code endIndex} or if {@code endIndex} is greater than
 868      *             {@code s.length()}.
 869      * @throws     NumberFormatException  if the {@code CharSequence} does not
 870      *             contain a parsable unsigned {@code int} in the specified
 871      *             {@code radix}, or if {@code radix} is either smaller than
 872      *             {@link java.lang.Character#MIN_RADIX} or larger than
 873      *             {@link java.lang.Character#MAX_RADIX}.
 874      * @since  9
 875      */
 876     public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix)
 877                 throws NumberFormatException {
 878         s = Objects.requireNonNull(s);
 879 
 880         if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
 881             throw new IndexOutOfBoundsException();
 882         }
 883         int start = beginIndex, len = endIndex - beginIndex;
 884 
 885         if (len > 0) {
 886             char firstChar = s.charAt(start);
 887             if (firstChar == '-') {
 888                 throw new
 889                     NumberFormatException(String.format("Illegal leading minus sign " +
 890                                                        "on unsigned string %s.", s));
 891             } else {
 892                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
 893                         (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits
 894                     return parseInt(s, start, start + len, radix);
 895                 } else {
 896                     long ell = Long.parseLong(s, start, start + len, radix);
 897                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
 898                         return (int) ell;
 899                     } else {
 900                         throw new
 901                             NumberFormatException(String.format("String value %s exceeds " +
 902                                                                 "range of unsigned int.", s));
 903                     }
 904                 }
 905             }
 906         } else {
 907             throw new NumberFormatException("");
 908         }
 909     }
 910 
 911     /**
 912      * Parses the string argument as an unsigned decimal integer. The
 913      * characters in the string must all be decimal digits, except
 914      * that the first character may be an ASCII plus sign {@code
 915      * '+'} ({@code '\u005Cu002B'}). The resulting integer value
 916      * is returned, exactly as if the argument and the radix 10 were
 917      * given as arguments to the {@link
 918      * #parseUnsignedInt(java.lang.String, int)} method.
 919      *
 920      * @param s   a {@code String} containing the unsigned {@code int}
 921      *            representation to be parsed
 922      * @return    the unsigned integer value represented by the argument in decimal.
 923      * @throws    NumberFormatException  if the string does not contain a
 924      *            parsable unsigned integer.
 925      * @since 1.8
 926      */
 927     public static int parseUnsignedInt(String s) throws NumberFormatException {
 928         return parseUnsignedInt(s, 10);
 929     }
 930 
 931     /**
 932      * Returns an {@code Integer} object holding the value
 933      * extracted from the specified {@code String} when parsed
 934      * with the radix given by the second argument. The first argument
 935      * is interpreted as representing a signed integer in the radix
 936      * specified by the second argument, exactly as if the arguments
 937      * were given to the {@link #parseInt(java.lang.String, int)}
 938      * method. The result is an {@code Integer} object that
 939      * represents the integer value specified by the string.
 940      *
 941      * <p>In other words, this method returns an {@code Integer}
 942      * object equal to the value of:
 943      *
 944      * <blockquote>
 945      *  {@code new Integer(Integer.parseInt(s, radix))}
 946      * </blockquote>
 947      *
 948      * @param      s   the string to be parsed.
 949      * @param      radix the radix to be used in interpreting {@code s}
 950      * @return     an {@code Integer} object holding the value
 951      *             represented by the string argument in the specified
 952      *             radix.
 953      * @exception NumberFormatException if the {@code String}
 954      *            does not contain a parsable {@code int}.
 955      */
 956     public static Integer valueOf(String s, int radix) throws NumberFormatException {
 957         return Integer.valueOf(parseInt(s,radix));
 958     }
 959 
 960     /**
 961      * Returns an {@code Integer} object holding the
 962      * value of the specified {@code String}. The argument is
 963      * interpreted as representing a signed decimal integer, exactly
 964      * as if the argument were given to the {@link
 965      * #parseInt(java.lang.String)} method. The result is an
 966      * {@code Integer} object that represents the integer value
 967      * 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))}
 974      * </blockquote>
 975      *
 976      * @param      s   the string to be parsed.
 977      * @return     an {@code Integer} object holding the value
 978      *             represented by the string argument.
 979      * @exception  NumberFormatException  if the string cannot be parsed
 980      *             as an integer.
 981      */
 982     public static Integer valueOf(String s) throws NumberFormatException {
 983         return Integer.valueOf(parseInt(s, 10));
 984     }
 985 
 986     /**
 987      * Cache to support the object identity semantics of autoboxing for values between
 988      * -128 and 127 (inclusive) as required by JLS.
 989      *
 990      * The cache is initialized on first usage.  The size of the cache
 991      * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
 992      * During VM initialization, java.lang.Integer.IntegerCache.high property
 993      * may be set and saved in the private system properties in the
 994      * jdk.internal.misc.VM class.
 995      *
 996      * WARNING: The cache is archived with CDS and reloaded from the shared
 997      * archive at runtime. The archived cache (Integer[]) and Integer objects
 998      * reside in the closed archive heap regions. Care should be taken when
 999      * changing the implementation and the cache array should not be assigned
1000      * with new Integer object(s) after initialization.
1001      */
1002 
1003     private static class IntegerCache {
1004         static final int low = -128;
1005         static final int high;
1006         static final Integer[] cache;
1007         static Integer[] archivedCache;
1008 
1009         static {
1010             // high value may be configured by property
1011             int h = 127;
1012             String integerCacheHighPropValue =
1013                 VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
1014             if (integerCacheHighPropValue != null) {
1015                 try {
1016                     h = Math.max(parseInt(integerCacheHighPropValue), 127);
1017                     // Maximum array size is Integer.MAX_VALUE
1018                     h = Math.min(h, Integer.MAX_VALUE - (-low) -1);
1019                 } catch( NumberFormatException nfe) {
1020                     // If the property cannot be parsed into an int, ignore it.
1021                 }
1022             }
1023             high = h;
1024 
1025             // Load IntegerCache.archivedCache from archive, if possible
1026             VM.initializeFromArchive(IntegerCache.class);
1027             int size = (high - low) + 1;
1028 
1029             // Use the archived cache if it exists and is large enough
1030             if (archivedCache == null || size > archivedCache.length) {
1031                 Integer[] c = new Integer[size];
1032                 int j = low;
1033                 for(int i = 0; i < c.length; i++) {
1034                     c[i] = new Integer(j++);
1035                 }
1036                 archivedCache = c;
1037             }
1038             cache = archivedCache;
1039             // range [-128, 127] must be interned (JLS7 5.1.7)
1040             assert IntegerCache.high >= 127;
1041         }
1042 
1043         private IntegerCache() {}
1044     }
1045 
1046     /**
1047      * Returns an {@code Integer} instance representing the specified
1048      * {@code int} value.  If a new {@code Integer} instance is not
1049      * required, this method should generally be used in preference to
1050      * the constructor {@link #Integer(int)}, as this method is likely
1051      * to yield significantly better space and time performance by
1052      * caching frequently requested values.
1053      *
1054      * This method will always cache values in the range -128 to 127,
1055      * inclusive, and may cache other values outside of this range.
1056      *
1057      * @param  i an {@code int} value.
1058      * @return an {@code Integer} instance representing {@code i}.
1059      * @since  1.5
1060      */
1061     @HotSpotIntrinsicCandidate
1062     public static Integer valueOf(int i) {
1063         if (i >= IntegerCache.low && i <= IntegerCache.high)
1064             return IntegerCache.cache[i + (-IntegerCache.low)];
1065         return new Integer(i);
1066     }
1067 
1068     /**
1069      * The value of the {@code Integer}.
1070      *
1071      * @serial
1072      */
1073     private final int value;
1074 
1075     /**
1076      * Constructs a newly allocated {@code Integer} object that
1077      * represents the specified {@code int} value.
1078      *
1079      * @param   value   the value to be represented by the
1080      *                  {@code Integer} object.
1081      *
1082      * @deprecated
1083      * It is rarely appropriate to use this constructor. The static factory
1084      * {@link #valueOf(int)} is generally a better choice, as it is
1085      * likely to yield significantly better space and time performance.
1086      */
1087     @Deprecated(since="9")
1088     public Integer(int value) {
1089         this.value = value;
1090     }
1091 
1092     /**
1093      * Constructs a newly allocated {@code Integer} object that
1094      * represents the {@code int} value indicated by the
1095      * {@code String} parameter. The string is converted to an
1096      * {@code int} value in exactly the manner used by the
1097      * {@code parseInt} method for radix 10.
1098      *
1099      * @param   s   the {@code String} to be converted to an {@code Integer}.
1100      * @throws      NumberFormatException if the {@code String} does not
1101      *              contain a parsable integer.
1102      *
1103      * @deprecated
1104      * It is rarely appropriate to use this constructor.
1105      * Use {@link #parseInt(String)} to convert a string to a
1106      * {@code int} primitive, or use {@link #valueOf(String)}
1107      * to convert a string to an {@code Integer} object.
1108      */
1109     @Deprecated(since="9")
1110     public Integer(String s) throws NumberFormatException {
1111         this.value = parseInt(s, 10);
1112     }
1113 
1114     /**
1115      * Returns the value of this {@code Integer} as a {@code byte}
1116      * after a narrowing primitive conversion.
1117      * @jls 5.1.3 Narrowing Primitive Conversions
1118      */
1119     public byte byteValue() {
1120         return (byte)value;
1121     }
1122 
1123     /**
1124      * Returns the value of this {@code Integer} as a {@code short}
1125      * after a narrowing primitive conversion.
1126      * @jls 5.1.3 Narrowing Primitive Conversions
1127      */
1128     public short shortValue() {
1129         return (short)value;
1130     }
1131 
1132     /**
1133      * Returns the value of this {@code Integer} as an
1134      * {@code int}.
1135      */
1136     @HotSpotIntrinsicCandidate
1137     public int intValue() {
1138         return value;
1139     }
1140 
1141     /**
1142      * Returns the value of this {@code Integer} as a {@code long}
1143      * after a widening primitive conversion.
1144      * @jls 5.1.2 Widening Primitive Conversions
1145      * @see Integer#toUnsignedLong(int)
1146      */
1147     public long longValue() {
1148         return (long)value;
1149     }
1150 
1151     /**
1152      * Returns the value of this {@code Integer} as a {@code float}
1153      * after a widening primitive conversion.
1154      * @jls 5.1.2 Widening Primitive Conversions
1155      */
1156     public float floatValue() {
1157         return (float)value;
1158     }
1159 
1160     /**
1161      * Returns the value of this {@code Integer} as a {@code double}
1162      * after a widening primitive conversion.
1163      * @jls 5.1.2 Widening Primitive Conversions
1164      */
1165     public double doubleValue() {
1166         return (double)value;
1167     }
1168 
1169     /**
1170      * Returns a {@code String} object representing this
1171      * {@code Integer}'s value. The value is converted to signed
1172      * decimal representation and returned as a string, exactly as if
1173      * the integer value were given as an argument to the {@link
1174      * java.lang.Integer#toString(int)} method.
1175      *
1176      * @return  a string representation of the value of this object in
1177      *          base&nbsp;10.
1178      */
1179     public String toString() {
1180         return toString(value);
1181     }
1182 
1183     /**
1184      * Returns a hash code for this {@code Integer}.
1185      *
1186      * @return  a hash code value for this object, equal to the
1187      *          primitive {@code int} value represented by this
1188      *          {@code Integer} object.
1189      */
1190     @Override
1191     public int hashCode() {
1192         return Integer.hashCode(value);
1193     }
1194 
1195     /**
1196      * Returns a hash code for an {@code int} value; compatible with
1197      * {@code Integer.hashCode()}.
1198      *
1199      * @param value the value to hash
1200      * @since 1.8
1201      *
1202      * @return a hash code value for an {@code int} value.
1203      */
1204     public static int hashCode(int value) {
1205         return value;
1206     }
1207 
1208     /**
1209      * Compares this object to the specified object.  The result is
1210      * {@code true} if and only if the argument is not
1211      * {@code null} and is an {@code Integer} object that
1212      * contains the same {@code int} value as this object.
1213      *
1214      * @param   obj   the object to compare with.
1215      * @return  {@code true} if the objects are the same;
1216      *          {@code false} otherwise.
1217      */
1218     public boolean equals(Object obj) {
1219         if (obj instanceof Integer) {
1220             return value == ((Integer)obj).intValue();
1221         }
1222         return false;
1223     }
1224 
1225     /**
1226      * Determines the integer value of the system property with the
1227      * specified name.
1228      *
1229      * <p>The first argument is treated as the name of a system
1230      * property.  System properties are accessible through the {@link
1231      * java.lang.System#getProperty(java.lang.String)} method. The
1232      * string value of this property is then interpreted as an integer
1233      * value using the grammar supported by {@link Integer#decode decode} and
1234      * an {@code Integer} object representing this value is returned.
1235      *
1236      * <p>If there is no property with the specified name, if the
1237      * specified name is empty or {@code null}, or if the property
1238      * does not have the correct numeric format, then {@code null} is
1239      * returned.
1240      *
1241      * <p>In other words, this method returns an {@code Integer}
1242      * object equal to the value of:
1243      *
1244      * <blockquote>
1245      *  {@code getInteger(nm, null)}
1246      * </blockquote>
1247      *
1248      * @param   nm   property name.
1249      * @return  the {@code Integer} value of the property.
1250      * @throws  SecurityException for the same reasons as
1251      *          {@link System#getProperty(String) System.getProperty}
1252      * @see     java.lang.System#getProperty(java.lang.String)
1253      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1254      */
1255     public static Integer getInteger(String nm) {
1256         return getInteger(nm, null);
1257     }
1258 
1259     /**
1260      * Determines the integer value of the system property with the
1261      * specified name.
1262      *
1263      * <p>The first argument is treated as the name of a system
1264      * property.  System properties are accessible through the {@link
1265      * java.lang.System#getProperty(java.lang.String)} method. The
1266      * string value of this property is then interpreted as an integer
1267      * value using the grammar supported by {@link Integer#decode decode} and
1268      * an {@code Integer} object representing this value is returned.
1269      *
1270      * <p>The second argument is the default value. An {@code Integer} object
1271      * that represents the value of the second argument is returned if there
1272      * is no property of the specified name, if the property does not have
1273      * the correct numeric format, or if the specified name is empty or
1274      * {@code null}.
1275      *
1276      * <p>In other words, this method returns an {@code Integer} object
1277      * equal to the value of:
1278      *
1279      * <blockquote>
1280      *  {@code getInteger(nm, new Integer(val))}
1281      * </blockquote>
1282      *
1283      * but in practice it may be implemented in a manner such as:
1284      *
1285      * <blockquote><pre>
1286      * Integer result = getInteger(nm, null);
1287      * return (result == null) ? new Integer(val) : result;
1288      * </pre></blockquote>
1289      *
1290      * to avoid the unnecessary allocation of an {@code Integer}
1291      * object when the default value is not needed.
1292      *
1293      * @param   nm   property name.
1294      * @param   val   default value.
1295      * @return  the {@code Integer} value of the property.
1296      * @throws  SecurityException for the same reasons as
1297      *          {@link System#getProperty(String) System.getProperty}
1298      * @see     java.lang.System#getProperty(java.lang.String)
1299      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)
1300      */
1301     public static Integer getInteger(String nm, int val) {
1302         Integer result = getInteger(nm, null);
1303         return (result == null) ? Integer.valueOf(val) : result;
1304     }
1305 
1306     /**
1307      * Returns the integer value of the system property with the
1308      * specified name.  The first argument is treated as the name of a
1309      * system property.  System properties are accessible through the
1310      * {@link java.lang.System#getProperty(java.lang.String)} method.
1311      * The string value of this property is then interpreted as an
1312      * integer value, as per the {@link Integer#decode decode} method,
1313      * and an {@code Integer} object representing this value is
1314      * returned; in summary:
1315      *
1316      * <ul><li>If the property value begins with the two ASCII characters
1317      *         {@code 0x} or the ASCII character {@code #}, not
1318      *      followed by a minus sign, then the rest of it is parsed as a
1319      *      hexadecimal integer exactly as by the method
1320      *      {@link #valueOf(java.lang.String, int)} with radix 16.
1321      * <li>If the property value begins with the ASCII character
1322      *     {@code 0} followed by another character, it is parsed as an
1323      *     octal integer exactly as by the method
1324      *     {@link #valueOf(java.lang.String, int)} with radix 8.
1325      * <li>Otherwise, the property value is parsed as a decimal integer
1326      * exactly as by the method {@link #valueOf(java.lang.String, int)}
1327      * with radix 10.
1328      * </ul>
1329      *
1330      * <p>The second argument is the default value. The default value is
1331      * returned if there is no property of the specified name, if the
1332      * property does not have the correct numeric format, or if the
1333      * specified name is empty or {@code null}.
1334      *
1335      * @param   nm   property name.
1336      * @param   val   default value.
1337      * @return  the {@code Integer} value of the property.
1338      * @throws  SecurityException for the same reasons as
1339      *          {@link System#getProperty(String) System.getProperty}
1340      * @see     System#getProperty(java.lang.String)
1341      * @see     System#getProperty(java.lang.String, java.lang.String)
1342      */
1343     public static Integer getInteger(String nm, Integer val) {
1344         String v = null;
1345         try {
1346             v = System.getProperty(nm);
1347         } catch (IllegalArgumentException | NullPointerException e) {
1348         }
1349         if (v != null) {
1350             try {
1351                 return Integer.decode(v);
1352             } catch (NumberFormatException e) {
1353             }
1354         }
1355         return val;
1356     }
1357 
1358     /**
1359      * Decodes a {@code String} into an {@code Integer}.
1360      * Accepts decimal, hexadecimal, and octal numbers given
1361      * by the following grammar:
1362      *
1363      * <blockquote>
1364      * <dl>
1365      * <dt><i>DecodableString:</i>
1366      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1367      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1368      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1369      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1370      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1371      *
1372      * <dt><i>Sign:</i>
1373      * <dd>{@code -}
1374      * <dd>{@code +}
1375      * </dl>
1376      * </blockquote>
1377      *
1378      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1379      * are as defined in section 3.10.1 of
1380      * <cite>The Java&trade; Language Specification</cite>,
1381      * except that underscores are not accepted between digits.
1382      *
1383      * <p>The sequence of characters following an optional
1384      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1385      * "{@code #}", or leading zero) is parsed as by the {@code
1386      * Integer.parseInt} method with the indicated radix (10, 16, or
1387      * 8).  This sequence of characters must represent a positive
1388      * value or a {@link NumberFormatException} will be thrown.  The
1389      * result is negated if first character of the specified {@code
1390      * String} is the minus sign.  No whitespace characters are
1391      * permitted in the {@code String}.
1392      *
1393      * @param     nm the {@code String} to decode.
1394      * @return    an {@code Integer} object holding the {@code int}
1395      *             value represented by {@code nm}
1396      * @exception NumberFormatException  if the {@code String} does not
1397      *            contain a parsable integer.
1398      * @see java.lang.Integer#parseInt(java.lang.String, int)
1399      */
1400     public static Integer decode(String nm) throws NumberFormatException {
1401         int radix = 10;
1402         int index = 0;
1403         boolean negative = false;
1404         Integer result;
1405 
1406         if (nm.length() == 0)
1407             throw new NumberFormatException("Zero length string");
1408         char firstChar = nm.charAt(0);
1409         // Handle sign, if present
1410         if (firstChar == '-') {
1411             negative = true;
1412             index++;
1413         } else if (firstChar == '+')
1414             index++;
1415 
1416         // Handle radix specifier, if present
1417         if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1418             index += 2;
1419             radix = 16;
1420         }
1421         else if (nm.startsWith("#", index)) {
1422             index ++;
1423             radix = 16;
1424         }
1425         else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1426             index ++;
1427             radix = 8;
1428         }
1429 
1430         if (nm.startsWith("-", index) || nm.startsWith("+", index))
1431             throw new NumberFormatException("Sign character in wrong position");
1432 
1433         try {
1434             result = Integer.valueOf(nm.substring(index), radix);
1435             result = negative ? Integer.valueOf(-result.intValue()) : result;
1436         } catch (NumberFormatException e) {
1437             // If number is Integer.MIN_VALUE, we'll end up here. The next line
1438             // handles this case, and causes any genuine format error to be
1439             // rethrown.
1440             String constant = negative ? ("-" + nm.substring(index))
1441                                        : nm.substring(index);
1442             result = Integer.valueOf(constant, radix);
1443         }
1444         return result;
1445     }
1446 
1447     /**
1448      * Compares two {@code Integer} objects numerically.
1449      *
1450      * @param   anotherInteger   the {@code Integer} to be compared.
1451      * @return  the value {@code 0} if this {@code Integer} is
1452      *          equal to the argument {@code Integer}; a value less than
1453      *          {@code 0} if this {@code Integer} is numerically less
1454      *          than the argument {@code Integer}; and a value greater
1455      *          than {@code 0} if this {@code Integer} is numerically
1456      *           greater than the argument {@code Integer} (signed
1457      *           comparison).
1458      * @since   1.2
1459      */
1460     public int compareTo(Integer anotherInteger) {
1461         return compare(this.value, anotherInteger.value);
1462     }
1463 
1464     /**
1465      * Compares two {@code int} values numerically.
1466      * The value returned is identical to what would be returned by:
1467      * <pre>
1468      *    Integer.valueOf(x).compareTo(Integer.valueOf(y))
1469      * </pre>
1470      *
1471      * @param  x the first {@code int} to compare
1472      * @param  y the second {@code int} to compare
1473      * @return the value {@code 0} if {@code x == y};
1474      *         a value less than {@code 0} if {@code x < y}; and
1475      *         a value greater than {@code 0} if {@code x > y}
1476      * @since 1.7
1477      */
1478     public static int compare(int x, int y) {
1479         return (x < y) ? -1 : ((x == y) ? 0 : 1);
1480     }
1481 
1482     /**
1483      * Compares two {@code int} values numerically treating the values
1484      * as unsigned.
1485      *
1486      * @param  x the first {@code int} to compare
1487      * @param  y the second {@code int} to compare
1488      * @return the value {@code 0} if {@code x == y}; a value less
1489      *         than {@code 0} if {@code x < y} as unsigned values; and
1490      *         a value greater than {@code 0} if {@code x > y} as
1491      *         unsigned values
1492      * @since 1.8
1493      */
1494     public static int compareUnsigned(int x, int y) {
1495         return compare(x + MIN_VALUE, y + MIN_VALUE);
1496     }
1497 
1498     /**
1499      * Converts the argument to a {@code long} by an unsigned
1500      * conversion.  In an unsigned conversion to a {@code long}, the
1501      * high-order 32 bits of the {@code long} are zero and the
1502      * low-order 32 bits are equal to the bits of the integer
1503      * argument.
1504      *
1505      * Consequently, zero and positive {@code int} values are mapped
1506      * to a numerically equal {@code long} value and negative {@code
1507      * int} values are mapped to a {@code long} value equal to the
1508      * input plus 2<sup>32</sup>.
1509      *
1510      * @param  x the value to convert to an unsigned {@code long}
1511      * @return the argument converted to {@code long} by an unsigned
1512      *         conversion
1513      * @since 1.8
1514      */
1515     public static long toUnsignedLong(int x) {
1516         return ((long) x) & 0xffffffffL;
1517     }
1518 
1519     /**
1520      * Returns the unsigned quotient of dividing the first argument by
1521      * the second where each argument and the result is interpreted as
1522      * an unsigned value.
1523      *
1524      * <p>Note that in two's complement arithmetic, the three other
1525      * basic arithmetic operations of add, subtract, and multiply are
1526      * bit-wise identical if the two operands are regarded as both
1527      * being signed or both being unsigned.  Therefore separate {@code
1528      * addUnsigned}, etc. methods are not provided.
1529      *
1530      * @param dividend the value to be divided
1531      * @param divisor the value doing the dividing
1532      * @return the unsigned quotient of the first argument divided by
1533      * the second argument
1534      * @see #remainderUnsigned
1535      * @since 1.8
1536      */
1537     public static int divideUnsigned(int dividend, int divisor) {
1538         // In lieu of tricky code, for now just use long arithmetic.
1539         return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1540     }
1541 
1542     /**
1543      * Returns the unsigned remainder from dividing the first argument
1544      * by the second where each argument and the result is interpreted
1545      * as an unsigned value.
1546      *
1547      * @param dividend the value to be divided
1548      * @param divisor the value doing the dividing
1549      * @return the unsigned remainder of the first argument divided by
1550      * the second argument
1551      * @see #divideUnsigned
1552      * @since 1.8
1553      */
1554     public static int remainderUnsigned(int dividend, int divisor) {
1555         // In lieu of tricky code, for now just use long arithmetic.
1556         return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1557     }
1558 
1559 
1560     // Bit twiddling
1561 
1562     /**
1563      * The number of bits used to represent an {@code int} value in two's
1564      * complement binary form.
1565      *
1566      * @since 1.5
1567      */
1568     @Native public static final int SIZE = 32;
1569 
1570     /**
1571      * The number of bytes used to represent an {@code int} value in two's
1572      * complement binary form.
1573      *
1574      * @since 1.8
1575      */
1576     public static final int BYTES = SIZE / Byte.SIZE;
1577 
1578     /**
1579      * Returns an {@code int} value with at most a single one-bit, in the
1580      * position of the highest-order ("leftmost") one-bit in the specified
1581      * {@code int} value.  Returns zero if the specified value has no
1582      * one-bits in its two's complement binary representation, that is, if it
1583      * is equal to zero.
1584      *
1585      * @param i the value whose highest one bit is to be computed
1586      * @return an {@code int} value with a single one-bit, in the position
1587      *     of the highest-order one-bit in the specified value, or zero if
1588      *     the specified value is itself equal to zero.
1589      * @since 1.5
1590      */
1591     public static int highestOneBit(int i) {
1592         return i & (MIN_VALUE >>> numberOfLeadingZeros(i));
1593     }
1594 
1595     /**
1596      * Returns an {@code int} value with at most a single one-bit, in the
1597      * position of the lowest-order ("rightmost") one-bit in the specified
1598      * {@code int} value.  Returns zero if the specified value has no
1599      * one-bits in its two's complement binary representation, that is, if it
1600      * is equal to zero.
1601      *
1602      * @param i the value whose lowest one bit is to be computed
1603      * @return an {@code int} value with a single one-bit, in the position
1604      *     of the lowest-order one-bit in the specified value, or zero if
1605      *     the specified value is itself equal to zero.
1606      * @since 1.5
1607      */
1608     public static int lowestOneBit(int i) {
1609         // HD, Section 2-1
1610         return i & -i;
1611     }
1612 
1613     /**
1614      * Returns the number of zero bits preceding the highest-order
1615      * ("leftmost") one-bit in the two's complement binary representation
1616      * of the specified {@code int} value.  Returns 32 if the
1617      * specified value has no one-bits in its two's complement representation,
1618      * in other words if it is equal to zero.
1619      *
1620      * <p>Note that this method is closely related to the logarithm base 2.
1621      * For all positive {@code int} values x:
1622      * <ul>
1623      * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1624      * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1625      * </ul>
1626      *
1627      * @param i the value whose number of leading zeros is to be computed
1628      * @return the number of zero bits preceding the highest-order
1629      *     ("leftmost") one-bit in the two's complement binary representation
1630      *     of the specified {@code int} value, or 32 if the value
1631      *     is equal to zero.
1632      * @since 1.5
1633      */
1634     @HotSpotIntrinsicCandidate
1635     public static int numberOfLeadingZeros(int i) {
1636         // HD, Count leading 0's
1637         if (i <= 0)
1638             return i == 0 ? 32 : 0;
1639         int n = 31;
1640         if (i >= 1 << 16) { n -= 16; i >>>= 16; }
1641         if (i >= 1 <<  8) { n -=  8; i >>>=  8; }
1642         if (i >= 1 <<  4) { n -=  4; i >>>=  4; }
1643         if (i >= 1 <<  2) { n -=  2; i >>>=  2; }
1644         return n - (i >>> 1);
1645     }
1646 
1647     /**
1648      * Returns the number of zero bits following the lowest-order ("rightmost")
1649      * one-bit in the two's complement binary representation of the specified
1650      * {@code int} value.  Returns 32 if the specified value has no
1651      * one-bits in its two's complement representation, in other words if it is
1652      * equal to zero.
1653      *
1654      * @param i the value whose number of trailing zeros is to be computed
1655      * @return the number of zero bits following the lowest-order ("rightmost")
1656      *     one-bit in the two's complement binary representation of the
1657      *     specified {@code int} value, or 32 if the value is equal
1658      *     to zero.
1659      * @since 1.5
1660      */
1661     @HotSpotIntrinsicCandidate
1662     public static int numberOfTrailingZeros(int i) {
1663         // HD, Count trailing 0's
1664         i = ~i & (i - 1);
1665         if (i <= 0) return i & 32;
1666         int n = 1;
1667         if (i > 1 << 16) { n += 16; i >>>= 16; }
1668         if (i > 1 <<  8) { n +=  8; i >>>=  8; }
1669         if (i > 1 <<  4) { n +=  4; i >>>=  4; }
1670         if (i > 1 <<  2) { n +=  2; i >>>=  2; }
1671         return n + (i >>> 1);
1672     }
1673 
1674     /**
1675      * Returns the number of one-bits in the two's complement binary
1676      * representation of the specified {@code int} value.  This function is
1677      * sometimes referred to as the <i>population count</i>.
1678      *
1679      * @param i the value whose bits are to be counted
1680      * @return the number of one-bits in the two's complement binary
1681      *     representation of the specified {@code int} value.
1682      * @since 1.5
1683      */
1684     @HotSpotIntrinsicCandidate
1685     public static int bitCount(int i) {
1686         // HD, Figure 5-2
1687         i = i - ((i >>> 1) & 0x55555555);
1688         i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1689         i = (i + (i >>> 4)) & 0x0f0f0f0f;
1690         i = i + (i >>> 8);
1691         i = i + (i >>> 16);
1692         return i & 0x3f;
1693     }
1694 
1695     /**
1696      * Returns the value obtained by rotating the two's complement binary
1697      * representation of the specified {@code int} value left by the
1698      * specified number of bits.  (Bits shifted out of the left hand, or
1699      * high-order, side reenter on the right, or low-order.)
1700      *
1701      * <p>Note that left rotation with a negative distance is equivalent to
1702      * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1703      * distance)}.  Note also that rotation by any multiple of 32 is a
1704      * no-op, so all but the last five bits of the rotation distance can be
1705      * ignored, even if the distance is negative: {@code rotateLeft(val,
1706      * distance) == rotateLeft(val, distance & 0x1F)}.
1707      *
1708      * @param i the value whose bits are to be rotated left
1709      * @param distance the number of bit positions to rotate left
1710      * @return the value obtained by rotating the two's complement binary
1711      *     representation of the specified {@code int} value left by the
1712      *     specified number of bits.
1713      * @since 1.5
1714      */
1715     public static int rotateLeft(int i, int distance) {
1716         return (i << distance) | (i >>> -distance);
1717     }
1718 
1719     /**
1720      * Returns the value obtained by rotating the two's complement binary
1721      * representation of the specified {@code int} value right by the
1722      * specified number of bits.  (Bits shifted out of the right hand, or
1723      * low-order, side reenter on the left, or high-order.)
1724      *
1725      * <p>Note that right rotation with a negative distance is equivalent to
1726      * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1727      * distance)}.  Note also that rotation by any multiple of 32 is a
1728      * no-op, so all but the last five bits of the rotation distance can be
1729      * ignored, even if the distance is negative: {@code rotateRight(val,
1730      * distance) == rotateRight(val, distance & 0x1F)}.
1731      *
1732      * @param i the value whose bits are to be rotated right
1733      * @param distance the number of bit positions to rotate right
1734      * @return the value obtained by rotating the two's complement binary
1735      *     representation of the specified {@code int} value right by the
1736      *     specified number of bits.
1737      * @since 1.5
1738      */
1739     public static int rotateRight(int i, int distance) {
1740         return (i >>> distance) | (i << -distance);
1741     }
1742 
1743     /**
1744      * Returns the value obtained by reversing the order of the bits in the
1745      * two's complement binary representation of the specified {@code int}
1746      * value.
1747      *
1748      * @param i the value to be reversed
1749      * @return the value obtained by reversing order of the bits in the
1750      *     specified {@code int} value.
1751      * @since 1.5
1752      */
1753     public static int reverse(int i) {
1754         // HD, Figure 7-1
1755         i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1756         i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1757         i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1758 
1759         return reverseBytes(i);
1760     }
1761 
1762     /**
1763      * Returns the signum function of the specified {@code int} value.  (The
1764      * return value is -1 if the specified value is negative; 0 if the
1765      * specified value is zero; and 1 if the specified value is positive.)
1766      *
1767      * @param i the value whose signum is to be computed
1768      * @return the signum function of the specified {@code int} value.
1769      * @since 1.5
1770      */
1771     public static int signum(int i) {
1772         // HD, Section 2-7
1773         return (i >> 31) | (-i >>> 31);
1774     }
1775 
1776     /**
1777      * Returns the value obtained by reversing the order of the bytes in the
1778      * two's complement representation of the specified {@code int} value.
1779      *
1780      * @param i the value whose bytes are to be reversed
1781      * @return the value obtained by reversing the bytes in the specified
1782      *     {@code int} value.
1783      * @since 1.5
1784      */
1785     @HotSpotIntrinsicCandidate
1786     public static int reverseBytes(int i) {
1787         return (i << 24)            |
1788                ((i & 0xff00) << 8)  |
1789                ((i >>> 8) & 0xff00) |
1790                (i >>> 24);
1791     }
1792 
1793     /**
1794      * Adds two integers together as per the + operator.
1795      *
1796      * @param a the first operand
1797      * @param b the second operand
1798      * @return the sum of {@code a} and {@code b}
1799      * @see java.util.function.BinaryOperator
1800      * @since 1.8
1801      */
1802     public static int sum(int a, int b) {
1803         return a + b;
1804     }
1805 
1806     /**
1807      * Returns the greater of two {@code int} values
1808      * as if by calling {@link Math#max(int, int) Math.max}.
1809      *
1810      * @param a the first operand
1811      * @param b the second operand
1812      * @return the greater of {@code a} and {@code b}
1813      * @see java.util.function.BinaryOperator
1814      * @since 1.8
1815      */
1816     public static int max(int a, int b) {
1817         return Math.max(a, b);
1818     }
1819 
1820     /**
1821      * Returns the smaller of two {@code int} values
1822      * as if by calling {@link Math#min(int, int) Math.min}.
1823      *
1824      * @param a the first operand
1825      * @param b the second operand
1826      * @return the smaller of {@code a} and {@code b}
1827      * @see java.util.function.BinaryOperator
1828      * @since 1.8
1829      */
1830     public static int min(int a, int b) {
1831         return Math.min(a, b);
1832     }
1833 
1834     /** use serialVersionUID from JDK 1.0.2 for interoperability */
1835     @Native private static final long serialVersionUID = 1360826667806852920L;
1836 }