1 /*
2 * Copyright (c) 1994, 2012, 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.Properties;
30
31 /**
32 * The {@code Integer} class wraps a value of the primitive type
33 * {@code int} in an object. An object of type {@code Integer}
34 * contains a single field whose type is {@code int}.
35 *
36 * <p>In addition, this class provides several methods for converting
37 * an {@code int} to a {@code String} and a {@code String} to an
38 * {@code int}, as well as other constants and methods useful when
39 * dealing with an {@code int}.
40 *
41 * <p>Implementation note: The implementations of the "bit twiddling"
42 * methods (such as {@link #highestOneBit(int) highestOneBit} and
43 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
44 * based on material from Henry S. Warren, Jr.'s <i>Hacker's
45 * Delight</i>, (Addison Wesley, 2002).
46 *
47 * @author Lee Boynton
48 * @author Arthur van Hoff
49 * @author Josh Bloch
50 * @author Joseph D. Darcy
51 * @since JDK1.0
52 */
53 public final class Integer extends Number implements Comparable<Integer> {
54 /**
55 * A constant holding the minimum value an {@code int} can
56 * have, -2<sup>31</sup>.
57 */
58 @Native public static final int MIN_VALUE = 0x80000000;
59
60 /**
61 * A constant holding the maximum value an {@code int} can
62 * have, 2<sup>31</sup>-1.
63 */
64 @Native public static final int MAX_VALUE = 0x7fffffff;
65
66 /**
67 * The {@code Class} instance representing the primitive type
68 * {@code int}.
69 *
70 * @since JDK1.1
71 */
72 @SuppressWarnings("unchecked")
73 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
74
75 /**
76 * All possible chars for representing a number as a String
77 */
78 final static char[] digits = {
79 '0' , '1' , '2' , '3' , '4' , '5' ,
80 '6' , '7' , '8' , '9' , 'a' , 'b' ,
81 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
82 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
83 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
84 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
85 };
86
87 /**
88 * Returns a string representation of the first argument in the
89 * radix specified by the second argument.
90 *
91 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
92 * or larger than {@code Character.MAX_RADIX}, then the radix
93 * {@code 10} is used instead.
94 *
95 * <p>If the first argument is negative, the first element of the
96 * result is the ASCII minus character {@code '-'}
97 * ({@code '\u005Cu002D'}). If the first argument is not
98 * negative, no sign character appears in the result.
99 *
100 * <p>The remaining characters of the result represent the magnitude
101 * of the first argument. If the magnitude is zero, it is
102 * represented by a single zero character {@code '0'}
103 * ({@code '\u005Cu0030'}); otherwise, the first character of
104 * the representation of the magnitude will not be the zero
105 * character. The following ASCII characters are used as digits:
106 *
107 * <blockquote>
108 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
109 * </blockquote>
110 *
111 * These are {@code '\u005Cu0030'} through
112 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
113 * {@code '\u005Cu007A'}. If {@code radix} is
114 * <var>N</var>, then the first <var>N</var> of these characters
115 * are used as radix-<var>N</var> digits in the order shown. Thus,
116 * the digits for hexadecimal (radix 16) are
117 * {@code 0123456789abcdef}. If uppercase letters are
118 * desired, the {@link java.lang.String#toUpperCase()} method may
119 * be called on the result:
120 *
121 * <blockquote>
122 * {@code Integer.toString(n, 16).toUpperCase()}
123 * </blockquote>
124 *
125 * @param i an integer to be converted to a string.
126 * @param radix the radix to use in the string representation.
127 * @return a string representation of the argument in the specified radix.
128 * @see java.lang.Character#MAX_RADIX
129 * @see java.lang.Character#MIN_RADIX
130 */
131 public static String toString(int i, int radix) {
132 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
133 radix = 10;
134
135 /* Use the faster version */
136 if (radix == 10) {
137 return toString(i);
138 }
139
140 char buf[] = new char[33];
141 boolean negative = (i < 0);
142 int charPos = 32;
143
144 if (!negative) {
145 i = -i;
146 }
147
148 while (i <= -radix) {
149 buf[charPos--] = digits[-(i % radix)];
150 i = i / radix;
151 }
152 buf[charPos] = digits[-i];
153
154 if (negative) {
155 buf[--charPos] = '-';
156 }
157
158 return new String(buf, charPos, (33 - charPos));
159 }
160
161 /**
162 * Returns a string representation of the first argument as an
163 * unsigned integer value in the radix specified by the second
164 * argument.
165 *
166 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
167 * or larger than {@code Character.MAX_RADIX}, then the radix
168 * {@code 10} is used instead.
169 *
170 * <p>Note that since the first argument is treated as an unsigned
171 * value, no leading sign character is printed.
172 *
173 * <p>If the magnitude is zero, it is represented by a single zero
174 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
175 * the first character of the representation of the magnitude will
176 * not be the zero character.
177 *
178 * <p>The behavior of radixes and the characters used as digits
179 * are the same as {@link #toString(int, int) toString}.
180 *
181 * @param i an integer to be converted to an unsigned string.
182 * @param radix the radix to use in the string representation.
183 * @return an unsigned string representation of the argument in the specified radix.
184 * @see #toString(int, int)
185 * @since 1.8
186 */
187 public static String toUnsignedString(int i, int radix) {
188 return Long.toString(toUnsignedLong(i), radix);
189 }
190
191 /**
192 * Returns a string representation of the integer argument as an
193 * unsigned integer in base 16.
194 *
195 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
196 * if the argument is negative; otherwise, it is equal to the
197 * argument. This value is converted to a string of ASCII digits
198 * in hexadecimal (base 16) with no extra leading
199 * {@code 0}s.
200 *
201 * <p>The value of the argument can be recovered from the returned
202 * string {@code s} by calling {@link
203 * Integer#parseUnsignedInt(String, int)
204 * Integer.parseUnsignedInt(s, 16)}.
205 *
206 * <p>If the unsigned magnitude is zero, it is represented by a
207 * single zero character {@code '0'} ({@code '\u005Cu0030'});
208 * otherwise, the first character of the representation of the
209 * unsigned magnitude will not be the zero character. The
210 * following characters are used as hexadecimal digits:
211 *
212 * <blockquote>
213 * {@code 0123456789abcdef}
214 * </blockquote>
215 *
216 * These are the characters {@code '\u005Cu0030'} through
217 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
218 * {@code '\u005Cu0066'}. If uppercase letters are
219 * desired, the {@link java.lang.String#toUpperCase()} method may
220 * be called on the result:
221 *
222 * <blockquote>
223 * {@code Integer.toHexString(n).toUpperCase()}
224 * </blockquote>
225 *
226 * @param i an integer to be converted to a string.
227 * @return the string representation of the unsigned integer value
228 * represented by the argument in hexadecimal (base 16).
229 * @see #parseUnsignedInt(String, int)
230 * @see #toUnsignedString(int, int)
231 * @since JDK1.0.2
232 */
233 public static String toHexString(int i) {
234 return toUnsignedString0(i, 4);
235 }
236
237 /**
238 * Returns a string representation of the integer argument as an
239 * unsigned integer in base 8.
240 *
241 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
242 * if the argument is negative; otherwise, it is equal to the
243 * argument. This value is converted to a string of ASCII digits
244 * in octal (base 8) with no extra leading {@code 0}s.
245 *
246 * <p>The value of the argument can be recovered from the returned
247 * string {@code s} by calling {@link
248 * Integer#parseUnsignedInt(String, int)
249 * Integer.parseUnsignedInt(s, 8)}.
250 *
251 * <p>If the unsigned magnitude is zero, it is represented by a
252 * single zero character {@code '0'} ({@code '\u005Cu0030'});
253 * otherwise, the first character of the representation of the
254 * unsigned magnitude will not be the zero character. The
255 * following characters are used as octal digits:
256 *
257 * <blockquote>
258 * {@code 01234567}
259 * </blockquote>
260 *
261 * These are the characters {@code '\u005Cu0030'} through
262 * {@code '\u005Cu0037'}.
263 *
264 * @param i an integer to be converted to a string.
265 * @return the string representation of the unsigned integer value
266 * represented by the argument in octal (base 8).
267 * @see #parseUnsignedInt(String, int)
268 * @see #toUnsignedString(int, int)
269 * @since JDK1.0.2
270 */
271 public static String toOctalString(int i) {
272 return toUnsignedString0(i, 3);
273 }
274
275 /**
276 * Returns a string representation of the integer argument as an
277 * unsigned integer in base 2.
278 *
279 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
280 * if the argument is negative; otherwise it is equal to the
281 * argument. This value is converted to a string of ASCII digits
282 * in binary (base 2) with no extra leading {@code 0}s.
283 *
284 * <p>The value of the argument can be recovered from the returned
285 * string {@code s} by calling {@link
286 * Integer#parseUnsignedInt(String, int)
287 * Integer.parseUnsignedInt(s, 2)}.
288 *
289 * <p>If the unsigned magnitude is zero, it is represented by a
290 * single zero character {@code '0'} ({@code '\u005Cu0030'});
291 * otherwise, the first character of the representation of the
292 * unsigned magnitude will not be the zero character. The
293 * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
294 * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
295 *
296 * @param i an integer to be converted to a string.
297 * @return the string representation of the unsigned integer value
298 * represented by the argument in binary (base 2).
299 * @see #parseUnsignedInt(String, int)
300 * @see #toUnsignedString(int, int)
301 * @since JDK1.0.2
302 */
303 public static String toBinaryString(int i) {
304 return toUnsignedString0(i, 1);
305 }
306
307 /**
308 * Convert the integer to an unsigned number.
309 */
310 private static String toUnsignedString0(int i, int shift) {
311 char[] buf = new char[32];
312 int charPos = 32;
313 int radix = 1 << shift;
314 int mask = radix - 1;
315 do {
316 buf[--charPos] = digits[i & mask];
317 i >>>= shift;
318 } while (i != 0);
319
320 return new String(buf, charPos, (32 - charPos));
321 }
322
323
324 final static char [] DigitTens = {
325 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
326 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
327 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
328 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
329 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
330 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
331 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
332 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
333 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
334 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
335 } ;
336
337 final static char [] DigitOnes = {
338 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
339 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
340 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
341 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
342 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
343 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
344 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
345 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
346 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
347 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
348 } ;
349
350 // I use the "invariant division by multiplication" trick to
351 // accelerate Integer.toString. In particular we want to
352 // avoid division by 10.
353 //
354 // The "trick" has roughly the same performance characteristics
355 // as the "classic" Integer.toString code on a non-JIT VM.
356 // The trick avoids .rem and .div calls but has a longer code
357 // path and is thus dominated by dispatch overhead. In the
358 // JIT case the dispatch overhead doesn't exist and the
359 // "trick" is considerably faster than the classic code.
360 //
361 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
362 // sequence.
363 //
364 // RE: Division by Invariant Integers using Multiplication
365 // T Gralund, P Montgomery
366 // ACM PLDI 1994
367 //
368
369 /**
370 * Returns a {@code String} object representing the
371 * specified integer. The argument is converted to signed decimal
372 * representation and returned as a string, exactly as if the
373 * argument and radix 10 were given as arguments to the {@link
374 * #toString(int, int)} method.
375 *
376 * @param i an integer to be converted.
377 * @return a string representation of the argument in base 10.
378 */
379 public static String toString(int i) {
380 if (i == Integer.MIN_VALUE)
381 return "-2147483648";
382 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
383 char[] buf = new char[size];
384 getChars(i, size, buf);
385 return new String(buf, true);
386 }
387
388 /**
389 * Returns a string representation of the argument as an unsigned
390 * decimal value.
391 *
392 * The argument is converted to unsigned decimal representation
393 * and returned as a string exactly as if the argument and radix
394 * 10 were given as arguments to the {@link #toUnsignedString(int,
395 * int)} method.
396 *
397 * @param i an integer to be converted to an unsigned string.
398 * @return an unsigned string representation of the argument.
399 * @see #toUnsignedString(int, int)
400 * @since 1.8
401 */
402 public static String toUnsignedString(int i) {
403 return Long.toString(toUnsignedLong(i));
404 }
405
406 /**
407 * Places characters representing the integer i into the
408 * character array buf. The characters are placed into
409 * the buffer backwards starting with the least significant
410 * digit at the specified index (exclusive), and working
411 * backwards from there.
412 *
413 * Will fail if i == Integer.MIN_VALUE
414 */
415 static void getChars(int i, int index, char[] buf) {
416 int q, r;
417 int charPos = index;
418 char sign = 0;
419
420 if (i < 0) {
421 sign = '-';
422 i = -i;
423 }
424
425 // Generate two digits per iteration
426 while (i >= 65536) {
427 q = i / 100;
428 // really: r = i - (q * 100);
429 r = i - ((q << 6) + (q << 5) + (q << 2));
430 i = q;
431 buf [--charPos] = DigitOnes[r];
432 buf [--charPos] = DigitTens[r];
433 }
434
435 // Fall thru to fast mode for smaller numbers
436 // assert(i <= 65536, i);
437 for (;;) {
438 q = (i * 52429) >>> (16+3);
439 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
440 buf [--charPos] = digits [r];
441 i = q;
442 if (i == 0) break;
443 }
444 if (sign != 0) {
445 buf [--charPos] = sign;
446 }
447 }
448
449 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
450 99999999, 999999999, Integer.MAX_VALUE };
451
452 // Requires positive x
453 static int stringSize(int x) {
454 for (int i=0; ; i++)
455 if (x <= sizeTable[i])
456 return i+1;
457 }
458
459 /**
460 * Parses the string argument as a signed integer in the radix
461 * specified by the second argument. The characters in the string
462 * must all be digits of the specified radix (as determined by
463 * whether {@link java.lang.Character#digit(char, int)} returns a
464 * nonnegative value), except that the first character may be an
465 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
466 * indicate a negative value or an ASCII plus sign {@code '+'}
467 * ({@code '\u005Cu002B'}) to indicate a positive value. The
468 * resulting integer value is returned.
469 *
470 * <p>An exception of type {@code NumberFormatException} is
471 * thrown if any of the following situations occurs:
472 * <ul>
473 * <li>The first argument is {@code null} or is a string of
474 * length zero.
475 *
476 * <li>The radix is either smaller than
477 * {@link java.lang.Character#MIN_RADIX} or
478 * larger than {@link java.lang.Character#MAX_RADIX}.
479 *
480 * <li>Any character of the string is not a digit of the specified
481 * radix, except that the first character may be a minus sign
482 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
483 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
484 * string is longer than length 1.
485 *
486 * <li>The value represented by the string is not a value of type
487 * {@code int}.
488 * </ul>
489 *
490 * <p>Examples:
491 * <blockquote><pre>
492 * parseInt("0", 10) returns 0
493 * parseInt("473", 10) returns 473
494 * parseInt("+42", 10) returns 42
495 * parseInt("-0", 10) returns 0
496 * parseInt("-FF", 16) returns -255
497 * parseInt("1100110", 2) returns 102
498 * parseInt("2147483647", 10) returns 2147483647
499 * parseInt("-2147483648", 10) returns -2147483648
500 * parseInt("2147483648", 10) throws a NumberFormatException
501 * parseInt("99", 8) throws a NumberFormatException
502 * parseInt("Kona", 10) throws a NumberFormatException
503 * parseInt("Kona", 27) returns 411787
504 * </pre></blockquote>
505 *
506 * @param s the {@code String} containing the integer
507 * representation to be parsed
508 * @param radix the radix to be used while parsing {@code s}.
509 * @return the integer represented by the string argument in the
510 * specified radix.
511 * @exception NumberFormatException if the {@code String}
512 * does not contain a parsable {@code int}.
513 */
514 public static int parseInt(String s, int radix)
515 throws NumberFormatException
516 {
517 /*
518 * WARNING: This method may be invoked early during VM initialization
519 * before IntegerCache is initialized. Care must be taken to not use
520 * the valueOf method.
521 */
522
523 if (s == null) {
524 throw new NumberFormatException("null");
525 }
526
527 if (radix < Character.MIN_RADIX) {
528 throw new NumberFormatException("radix " + radix +
529 " less than Character.MIN_RADIX");
530 }
531
532 if (radix > Character.MAX_RADIX) {
533 throw new NumberFormatException("radix " + radix +
534 " greater than Character.MAX_RADIX");
535 }
536
537 int result = 0;
538 boolean negative = false;
539 int i = 0, len = s.length();
540 int limit = -Integer.MAX_VALUE;
541 int multmin;
542 int digit;
543
544 if (len > 0) {
545 char firstChar = s.charAt(0);
546 if (firstChar < '0') { // Possible leading "+" or "-"
547 if (firstChar == '-') {
548 negative = true;
549 limit = Integer.MIN_VALUE;
550 } else if (firstChar != '+')
551 throw NumberFormatException.forInputString(s);
552
553 if (len == 1) // Cannot have lone "+" or "-"
554 throw NumberFormatException.forInputString(s);
555 i++;
556 }
557 multmin = limit / radix;
558 while (i < len) {
559 // Accumulating negatively avoids surprises near MAX_VALUE
560 digit = Character.digit(s.charAt(i++),radix);
561 if (digit < 0) {
562 throw NumberFormatException.forInputString(s);
563 }
564 if (result < multmin) {
565 throw NumberFormatException.forInputString(s);
566 }
567 result *= radix;
568 if (result < limit + digit) {
569 throw NumberFormatException.forInputString(s);
570 }
571 result -= digit;
572 }
573 } else {
574 throw NumberFormatException.forInputString(s);
575 }
576 return negative ? result : -result;
577 }
578
579 /**
580 * Parses the string argument as a signed decimal integer. The
581 * characters in the string must all be decimal digits, except
582 * that the first character may be an ASCII minus sign {@code '-'}
583 * ({@code '\u005Cu002D'}) to indicate a negative value or an
584 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
585 * indicate a positive value. The resulting integer value is
586 * returned, exactly as if the argument and the radix 10 were
587 * given as arguments to the {@link #parseInt(java.lang.String,
588 * int)} method.
589 *
590 * @param s a {@code String} containing the {@code int}
591 * representation to be parsed
592 * @return the integer value represented by the argument in decimal.
593 * @exception NumberFormatException if the string does not contain a
594 * parsable integer.
595 */
596 public static int parseInt(String s) throws NumberFormatException {
597 return parseInt(s,10);
598 }
599
600 /**
601 * Parses the string argument as an unsigned integer in the radix
602 * specified by the second argument. An unsigned integer maps the
603 * values usually associated with negative numbers to positive
604 * numbers larger than {@code MAX_VALUE}.
605 *
606 * The characters in the string must all be digits of the
607 * specified radix (as determined by whether {@link
608 * java.lang.Character#digit(char, int)} returns a nonnegative
609 * value), except that the first character may be an ASCII plus
610 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
611 * integer value is returned.
612 *
613 * <p>An exception of type {@code NumberFormatException} is
614 * thrown if any of the following situations occurs:
615 * <ul>
616 * <li>The first argument is {@code null} or is a string of
617 * length zero.
618 *
619 * <li>The radix is either smaller than
620 * {@link java.lang.Character#MIN_RADIX} or
621 * larger than {@link java.lang.Character#MAX_RADIX}.
622 *
623 * <li>Any character of the string is not a digit of the specified
624 * radix, except that the first character may be a plus sign
625 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
626 * string is longer than length 1.
627 *
628 * <li>The value represented by the string is larger than the
629 * largest unsigned {@code int}, 2<sup>32</sup>-1.
630 *
631 * </ul>
632 *
633 *
634 * @param s the {@code String} containing the unsigned integer
635 * representation to be parsed
636 * @param radix the radix to be used while parsing {@code s}.
637 * @return the integer represented by the string argument in the
638 * specified radix.
639 * @throws NumberFormatException if the {@code String}
640 * does not contain a parsable {@code int}.
641 * @since 1.8
642 */
643 public static int parseUnsignedInt(String s, int radix)
644 throws NumberFormatException {
645 if (s == null) {
646 throw new NumberFormatException("null");
647 }
648
649 int len = s.length();
650 if (len > 0) {
651 char firstChar = s.charAt(0);
652 if (firstChar == '-') {
653 throw new
654 NumberFormatException(String.format("Illegal leading minus sign " +
655 "on unsigned string %s.", s));
656 } else {
657 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
658 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
659 return parseInt(s, radix);
660 } else {
661 long ell = Long.parseLong(s, radix);
662 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
663 return (int) ell;
664 } else {
665 throw new
666 NumberFormatException(String.format("String value %s exceeds " +
667 "range of unsigned int.", s));
668 }
669 }
670 }
671 } else {
672 throw NumberFormatException.forInputString(s);
673 }
674 }
675
676 /**
677 * Parses the string argument as an unsigned decimal integer. The
678 * characters in the string must all be decimal digits, except
679 * that the first character may be an an ASCII plus sign {@code
680 * '+'} ({@code '\u005Cu002B'}). The resulting integer value
681 * is returned, exactly as if the argument and the radix 10 were
682 * given as arguments to the {@link
683 * #parseUnsignedInt(java.lang.String, int)} method.
684 *
685 * @param s a {@code String} containing the unsigned {@code int}
686 * representation to be parsed
687 * @return the unsigned integer value represented by the argument in decimal.
688 * @throws NumberFormatException if the string does not contain a
689 * parsable unsigned integer.
690 * @since 1.8
691 */
692 public static int parseUnsignedInt(String s) throws NumberFormatException {
693 return parseUnsignedInt(s, 10);
694 }
695
696 /**
697 * Returns an {@code Integer} object holding the value
698 * extracted from the specified {@code String} when parsed
699 * with the radix given by the second argument. The first argument
700 * is interpreted as representing a signed integer in the radix
701 * specified by the second argument, exactly as if the arguments
702 * were given to the {@link #parseInt(java.lang.String, int)}
703 * method. The result is an {@code Integer} object that
704 * represents the integer value specified by the string.
705 *
706 * <p>In other words, this method returns an {@code Integer}
707 * object equal to the value of:
708 *
709 * <blockquote>
710 * {@code new Integer(Integer.parseInt(s, radix))}
711 * </blockquote>
712 *
713 * @param s the string to be parsed.
714 * @param radix the radix to be used in interpreting {@code s}
715 * @return an {@code Integer} object holding the value
716 * represented by the string argument in the specified
717 * radix.
718 * @exception NumberFormatException if the {@code String}
719 * does not contain a parsable {@code int}.
720 */
721 public static Integer valueOf(String s, int radix) throws NumberFormatException {
722 return Integer.valueOf(parseInt(s,radix));
723 }
724
725 /**
726 * Returns an {@code Integer} object holding the
727 * value of the specified {@code String}. The argument is
728 * interpreted as representing a signed decimal integer, exactly
729 * as if the argument were given to the {@link
730 * #parseInt(java.lang.String)} method. The result is an
731 * {@code Integer} object that represents the integer value
732 * specified by the string.
733 *
734 * <p>In other words, this method returns an {@code Integer}
735 * object equal to the value of:
736 *
737 * <blockquote>
738 * {@code new Integer(Integer.parseInt(s))}
739 * </blockquote>
740 *
741 * @param s the string to be parsed.
742 * @return an {@code Integer} object holding the value
743 * represented by the string argument.
744 * @exception NumberFormatException if the string cannot be parsed
745 * as an integer.
746 */
747 public static Integer valueOf(String s) throws NumberFormatException {
748 return Integer.valueOf(parseInt(s, 10));
749 }
750
751 /**
752 * Cache to support the object identity semantics of autoboxing for values between
753 * -128 and 127 (inclusive) as required by JLS.
754 *
755 * The cache is initialized on first usage. The size of the cache
756 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
757 * During VM initialization, java.lang.Integer.IntegerCache.high property
758 * may be set and saved in the private system properties in the
759 * sun.misc.VM class.
760 */
761
762 private static class IntegerCache {
763 static final int low = -128;
764 static final int high;
765 static final Integer cache[];
766
767 static {
768 // high value may be configured by property
769 int h = 127;
770 String integerCacheHighPropValue =
771 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
772 if (integerCacheHighPropValue != null) {
773 int i = parseInt(integerCacheHighPropValue);
774 i = Math.max(i, 127);
775 // Maximum array size is Integer.MAX_VALUE
776 h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
777 }
778 high = h;
779
780 cache = new Integer[(high - low) + 1];
781 int j = low;
782 for(int k = 0; k < cache.length; k++)
783 cache[k] = new Integer(j++);
784
785 // range [-128, 127] must be interned (JLS7 5.1.7)
786 assert IntegerCache.high >= 127;
787 }
788
789 private IntegerCache() {}
790 }
791
792 /**
793 * Returns an {@code Integer} instance representing the specified
794 * {@code int} value. If a new {@code Integer} instance is not
795 * required, this method should generally be used in preference to
796 * the constructor {@link #Integer(int)}, as this method is likely
797 * to yield significantly better space and time performance by
798 * caching frequently requested values.
799 *
800 * This method will always cache values in the range -128 to 127,
801 * inclusive, and may cache other values outside of this range.
802 *
803 * @param i an {@code int} value.
804 * @return an {@code Integer} instance representing {@code i}.
805 * @since 1.5
806 */
807 public static Integer valueOf(int i) {
808 if (i >= IntegerCache.low && i <= IntegerCache.high)
809 return IntegerCache.cache[i + (-IntegerCache.low)];
810 return new Integer(i);
811 }
812
813 /**
814 * The value of the {@code Integer}.
815 *
816 * @serial
817 */
818 private final int value;
819
820 /**
821 * Constructs a newly allocated {@code Integer} object that
822 * represents the specified {@code int} value.
823 *
824 * @param value the value to be represented by the
825 * {@code Integer} object.
826 */
827 public Integer(int value) {
828 this.value = value;
829 }
830
831 /**
832 * Constructs a newly allocated {@code Integer} object that
833 * represents the {@code int} value indicated by the
834 * {@code String} parameter. The string is converted to an
835 * {@code int} value in exactly the manner used by the
836 * {@code parseInt} method for radix 10.
837 *
838 * @param s the {@code String} to be converted to an
839 * {@code Integer}.
840 * @exception NumberFormatException if the {@code String} does not
841 * contain a parsable integer.
842 * @see java.lang.Integer#parseInt(java.lang.String, int)
843 */
844 public Integer(String s) throws NumberFormatException {
845 this.value = parseInt(s, 10);
846 }
847
848 /**
849 * Returns the value of this {@code Integer} as a {@code byte}
850 * after a narrowing primitive conversion.
851 * @jls 5.1.3 Narrowing Primitive Conversions
852 */
853 public byte byteValue() {
854 return (byte)value;
855 }
856
857 /**
858 * Returns the value of this {@code Integer} as a {@code short}
859 * after a narrowing primitive conversion.
860 * @jls 5.1.3 Narrowing Primitive Conversions
861 */
862 public short shortValue() {
863 return (short)value;
864 }
865
866 /**
867 * Returns the value of this {@code Integer} as an
868 * {@code int}.
869 */
870 public int intValue() {
871 return value;
872 }
873
874 /**
875 * Returns the value of this {@code Integer} as a {@code long}
876 * after a widening primitive conversion.
877 * @jls 5.1.2 Widening Primitive Conversions
878 */
879 public long longValue() {
880 return (long)value;
881 }
882
883 /**
884 * Returns the value of this {@code Integer} as a {@code float}
885 * after a widening primitive conversion.
886 * @jls 5.1.2 Widening Primitive Conversions
887 */
888 public float floatValue() {
889 return (float)value;
890 }
891
892 /**
893 * Returns the value of this {@code Integer} as a {@code double}
894 * after a widening primitive conversion.
895 * @jls 5.1.2 Widening Primitive Conversions
896 */
897 public double doubleValue() {
898 return (double)value;
899 }
900
901 /**
902 * Returns a {@code String} object representing this
903 * {@code Integer}'s value. The value is converted to signed
904 * decimal representation and returned as a string, exactly as if
905 * the integer value were given as an argument to the {@link
906 * java.lang.Integer#toString(int)} method.
907 *
908 * @return a string representation of the value of this object in
909 * base 10.
910 */
911 public String toString() {
912 return toString(value);
913 }
914
915 /**
916 * Returns a hash code for this {@code Integer}.
917 *
918 * @return a hash code value for this object, equal to the
919 * primitive {@code int} value represented by this
920 * {@code Integer} object.
921 */
922 @Override
923 public int hashCode() {
924 return Integer.hashCode(value);
925 }
926
927 /**
928 * Returns a hash code for a {@code int} value; compatible with
929 * {@code Integer.hashCode()}.
930 *
931 * @since 1.8
932 *
933 * @return a hash code value for a {@code int} value.
934 */
935 public static int hashCode(int value) {
936 return value;
937 }
938
939 /**
940 * Compares this object to the specified object. The result is
941 * {@code true} if and only if the argument is not
942 * {@code null} and is an {@code Integer} object that
943 * contains the same {@code int} value as this object.
944 *
945 * @param obj the object to compare with.
946 * @return {@code true} if the objects are the same;
947 * {@code false} otherwise.
948 */
949 public boolean equals(Object obj) {
950 if (obj instanceof Integer) {
951 return value == ((Integer)obj).intValue();
952 }
953 return false;
954 }
955
956 /**
957 * Determines the integer value of the system property with the
958 * specified name.
959 *
960 * <p>The first argument is treated as the name of a system
961 * property. System properties are accessible through the {@link
962 * java.lang.System#getProperty(java.lang.String)} method. The
963 * string value of this property is then interpreted as an integer
964 * value using the grammar supported by {@link Integer#decode decode} and
965 * an {@code Integer} object representing this value is returned.
966 *
967 * <p>If there is no property with the specified name, if the
968 * specified name is empty or {@code null}, or if the property
969 * does not have the correct numeric format, then {@code null} is
970 * returned.
971 *
972 * <p>In other words, this method returns an {@code Integer}
973 * object equal to the value of:
974 *
975 * <blockquote>
976 * {@code getInteger(nm, null)}
977 * </blockquote>
978 *
979 * @param nm property name.
980 * @return the {@code Integer} value of the property.
981 * @throws SecurityException for the same reasons as
982 * {@link System#getProperty(String) System.getProperty}
983 * @see java.lang.System#getProperty(java.lang.String)
984 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
985 */
986 public static Integer getInteger(String nm) {
987 return getInteger(nm, null);
988 }
989
990 /**
991 * Determines the integer value of the system property with the
992 * specified name.
993 *
994 * <p>The first argument is treated as the name of a system
995 * property. System properties are accessible through the {@link
996 * java.lang.System#getProperty(java.lang.String)} method. The
997 * string value of this property is then interpreted as an integer
998 * value using the grammar supported by {@link Integer#decode decode} and
999 * an {@code Integer} object representing this value is returned.
1000 *
1001 * <p>The second argument is the default value. An {@code Integer} object
1002 * that represents the value of the second argument is returned if there
1003 * is no property of the specified name, if the property does not have
1004 * the correct numeric format, or if the specified name is empty or
1005 * {@code null}.
1006 *
1007 * <p>In other words, this method returns an {@code Integer} object
1008 * equal to the value of:
1009 *
1010 * <blockquote>
1011 * {@code getInteger(nm, new Integer(val))}
1012 * </blockquote>
1013 *
1014 * but in practice it may be implemented in a manner such as:
1015 *
1016 * <blockquote><pre>
1017 * Integer result = getInteger(nm, null);
1018 * return (result == null) ? new Integer(val) : result;
1019 * </pre></blockquote>
1020 *
1021 * to avoid the unnecessary allocation of an {@code Integer}
1022 * object when the default value is not needed.
1023 *
1024 * @param nm property name.
1025 * @param val default value.
1026 * @return the {@code Integer} value of the property.
1027 * @throws SecurityException for the same reasons as
1028 * {@link System#getProperty(String) System.getProperty}
1029 * @see java.lang.System#getProperty(java.lang.String)
1030 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1031 */
1032 public static Integer getInteger(String nm, int val) {
1033 Integer result = getInteger(nm, null);
1034 return (result == null) ? Integer.valueOf(val) : result;
1035 }
1036
1037 /**
1038 * Returns the integer value of the system property with the
1039 * specified name. The first argument is treated as the name of a
1040 * system property. System properties are accessible through the
1041 * {@link java.lang.System#getProperty(java.lang.String)} method.
1042 * The string value of this property is then interpreted as an
1043 * integer value, as per the {@link Integer#decode decode} method,
1044 * and an {@code Integer} object representing this value is
1045 * returned; in summary:
1046 *
1047 * <ul><li>If the property value begins with the two ASCII characters
1048 * {@code 0x} or the ASCII character {@code #}, not
1049 * followed by a minus sign, then the rest of it is parsed as a
1050 * hexadecimal integer exactly as by the method
1051 * {@link #valueOf(java.lang.String, int)} with radix 16.
1052 * <li>If the property value begins with the ASCII character
1053 * {@code 0} followed by another character, it is parsed as an
1054 * octal integer exactly as by the method
1055 * {@link #valueOf(java.lang.String, int)} with radix 8.
1056 * <li>Otherwise, the property value is parsed as a decimal integer
1057 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1058 * with radix 10.
1059 * </ul>
1060 *
1061 * <p>The second argument is the default value. The default value is
1062 * returned if there is no property of the specified name, if the
1063 * property does not have the correct numeric format, or if the
1064 * specified name is empty or {@code null}.
1065 *
1066 * @param nm property name.
1067 * @param val default value.
1068 * @return the {@code Integer} value of the property.
1069 * @throws SecurityException for the same reasons as
1070 * {@link System#getProperty(String) System.getProperty}
1071 * @see System#getProperty(java.lang.String)
1072 * @see System#getProperty(java.lang.String, java.lang.String)
1073 */
1074 public static Integer getInteger(String nm, Integer val) {
1075 String v = null;
1076 try {
1077 v = System.getProperty(nm);
1078 } catch (IllegalArgumentException | NullPointerException e) {
1079 }
1080 if (v != null) {
1081 try {
1082 return Integer.decode(v);
1083 } catch (NumberFormatException e) {
1084 }
1085 }
1086 return val;
1087 }
1088
1089 /**
1090 * Decodes a {@code String} into an {@code Integer}.
1091 * Accepts decimal, hexadecimal, and octal numbers given
1092 * by the following grammar:
1093 *
1094 * <blockquote>
1095 * <dl>
1096 * <dt><i>DecodableString:</i>
1097 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1098 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1099 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1100 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1101 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1102 * <p>
1103 * <dt><i>Sign:</i>
1104 * <dd>{@code -}
1105 * <dd>{@code +}
1106 * </dl>
1107 * </blockquote>
1108 *
1109 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1110 * are as defined in section 3.10.1 of
1111 * <cite>The Java™ Language Specification</cite>,
1112 * except that underscores are not accepted between digits.
1113 *
1114 * <p>The sequence of characters following an optional
1115 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1116 * "{@code #}", or leading zero) is parsed as by the {@code
1117 * Integer.parseInt} method with the indicated radix (10, 16, or
1118 * 8). This sequence of characters must represent a positive
1119 * value or a {@link NumberFormatException} will be thrown. The
1120 * result is negated if first character of the specified {@code
1121 * String} is the minus sign. No whitespace characters are
1122 * permitted in the {@code String}.
1123 *
1124 * @param nm the {@code String} to decode.
1125 * @return an {@code Integer} object holding the {@code int}
1126 * value represented by {@code nm}
1127 * @exception NumberFormatException if the {@code String} does not
1128 * contain a parsable integer.
1129 * @see java.lang.Integer#parseInt(java.lang.String, int)
1130 */
1131 public static Integer decode(String nm) throws NumberFormatException {
1132 int radix = 10;
1133 int index = 0;
1134 boolean negative = false;
1135 Integer result;
1136
1137 if (nm.length() == 0)
1138 throw new NumberFormatException("Zero length string");
1139 char firstChar = nm.charAt(0);
1140 // Handle sign, if present
1141 if (firstChar == '-') {
1142 negative = true;
1143 index++;
1144 } else if (firstChar == '+')
1145 index++;
1146
1147 // Handle radix specifier, if present
1148 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1149 index += 2;
1150 radix = 16;
1151 }
1152 else if (nm.startsWith("#", index)) {
1153 index ++;
1154 radix = 16;
1155 }
1156 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1157 index ++;
1158 radix = 8;
1159 }
1160
1161 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1162 throw new NumberFormatException("Sign character in wrong position");
1163
1164 try {
1165 result = Integer.valueOf(nm.substring(index), radix);
1166 result = negative ? Integer.valueOf(-result.intValue()) : result;
1167 } catch (NumberFormatException e) {
1168 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1169 // handles this case, and causes any genuine format error to be
1170 // rethrown.
1171 String constant = negative ? ("-" + nm.substring(index))
1172 : nm.substring(index);
1173 result = Integer.valueOf(constant, radix);
1174 }
1175 return result;
1176 }
1177
1178 /**
1179 * Compares two {@code Integer} objects numerically.
1180 *
1181 * @param anotherInteger the {@code Integer} to be compared.
1182 * @return the value {@code 0} if this {@code Integer} is
1183 * equal to the argument {@code Integer}; a value less than
1184 * {@code 0} if this {@code Integer} is numerically less
1185 * than the argument {@code Integer}; and a value greater
1186 * than {@code 0} if this {@code Integer} is numerically
1187 * greater than the argument {@code Integer} (signed
1188 * comparison).
1189 * @since 1.2
1190 */
1191 public int compareTo(Integer anotherInteger) {
1192 return compare(this.value, anotherInteger.value);
1193 }
1194
1195 /**
1196 * Compares two {@code int} values numerically.
1197 * The value returned is identical to what would be returned by:
1198 * <pre>
1199 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1200 * </pre>
1201 *
1202 * @param x the first {@code int} to compare
1203 * @param y the second {@code int} to compare
1204 * @return the value {@code 0} if {@code x == y};
1205 * a value less than {@code 0} if {@code x < y}; and
1206 * a value greater than {@code 0} if {@code x > y}
1207 * @since 1.7
1208 */
1209 public static int compare(int x, int y) {
1210 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1211 }
1212
1213 /**
1214 * Compares two {@code int} values numerically treating the values
1215 * as unsigned.
1216 *
1217 * @param x the first {@code int} to compare
1218 * @param y the second {@code int} to compare
1219 * @return the value {@code 0} if {@code x == y}; a value less
1220 * than {@code 0} if {@code x < y} as unsigned values; and
1221 * a value greater than {@code 0} if {@code x > y} as
1222 * unsigned values
1223 * @since 1.8
1224 */
1225 public static int compareUnsigned(int x, int y) {
1226 return compare(x + MIN_VALUE, y + MIN_VALUE);
1227 }
1228
1229 /**
1230 * Converts the argument to a {@code long} by an unsigned
1231 * conversion. In an unsigned conversion to a {@code long}, the
1232 * high-order 32 bits of the {@code long} are zero and the
1233 * low-order 32 bits are equal to the bits of the integer
1234 * argument.
1235 *
1236 * Consequently, zero and positive {@code int} values are mapped
1237 * to a numerically equal {@code long} value and negative {@code
1238 * int} values are mapped to a {@code long} value equal to the
1239 * input plus 2<sup>32</sup>.
1240 *
1241 * @param x the value to convert to an unsigned {@code long}
1242 * @return the argument converted to {@code long} by an unsigned
1243 * conversion
1244 * @since 1.8
1245 */
1246 public static long toUnsignedLong(int x) {
1247 return ((long) x) & 0xffffffffL;
1248 }
1249
1250 /**
1251 * Returns the unsigned quotient of dividing the first argument by
1252 * the second where each argument and the result is interpreted as
1253 * an unsigned value.
1254 *
1255 * <p>Note that in two's complement arithmetic, the three other
1256 * basic arithmetic operations of add, subtract, and multiply are
1257 * bit-wise identical if the two operands are regarded as both
1258 * being signed or both being unsigned. Therefore separate {@code
1259 * addUnsigned}, etc. methods are not provided.
1260 *
1261 * @param dividend the value to be divided
1262 * @param divisor the value doing the dividing
1263 * @return the unsigned quotient of the first argument divided by
1264 * the second argument
1265 * @see #remainderUnsigned
1266 * @since 1.8
1267 */
1268 public static int divideUnsigned(int dividend, int divisor) {
1269 // In lieu of tricky code, for now just use long arithmetic.
1270 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1271 }
1272
1273 /**
1274 * Returns the unsigned remainder from dividing the first argument
1275 * by the second where each argument and the result is interpreted
1276 * as an unsigned value.
1277 *
1278 * @param dividend the value to be divided
1279 * @param divisor the value doing the dividing
1280 * @return the unsigned remainder of the first argument divided by
1281 * the second argument
1282 * @see #divideUnsigned
1283 * @since 1.8
1284 */
1285 public static int remainderUnsigned(int dividend, int divisor) {
1286 // In lieu of tricky code, for now just use long arithmetic.
1287 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1288 }
1289
1290
1291 // Bit twiddling
1292
1293 /**
1294 * The number of bits used to represent an {@code int} value in two's
1295 * complement binary form.
1296 *
1297 * @since 1.5
1298 */
1299 @Native public static final int SIZE = 32;
1300
1301 /**
1302 * The number of bytes used to represent a {@code int} value in two's
1303 * complement binary form.
1304 *
1305 * @since 1.8
1306 */
1307 public static final int BYTES = SIZE / Byte.SIZE;
1308
1309 /**
1310 * Returns an {@code int} value with at most a single one-bit, in the
1311 * position of the highest-order ("leftmost") one-bit in the specified
1312 * {@code int} value. Returns zero if the specified value has no
1313 * one-bits in its two's complement binary representation, that is, if it
1314 * is equal to zero.
1315 *
1316 * @return an {@code int} value with a single one-bit, in the position
1317 * of the highest-order one-bit in the specified value, or zero if
1318 * the specified value is itself equal to zero.
1319 * @since 1.5
1320 */
1321 public static int highestOneBit(int i) {
1322 // HD, Figure 3-1
1323 i |= (i >> 1);
1324 i |= (i >> 2);
1325 i |= (i >> 4);
1326 i |= (i >> 8);
1327 i |= (i >> 16);
1328 return i - (i >>> 1);
1329 }
1330
1331 /**
1332 * Returns an {@code int} value with at most a single one-bit, in the
1333 * position of the lowest-order ("rightmost") one-bit in the specified
1334 * {@code int} value. Returns zero if the specified value has no
1335 * one-bits in its two's complement binary representation, that is, if it
1336 * is equal to zero.
1337 *
1338 * @return an {@code int} value with a single one-bit, in the position
1339 * of the lowest-order one-bit in the specified value, or zero if
1340 * the specified value is itself equal to zero.
1341 * @since 1.5
1342 */
1343 public static int lowestOneBit(int i) {
1344 // HD, Section 2-1
1345 return i & -i;
1346 }
1347
1348 /**
1349 * Returns the number of zero bits preceding the highest-order
1350 * ("leftmost") one-bit in the two's complement binary representation
1351 * of the specified {@code int} value. Returns 32 if the
1352 * specified value has no one-bits in its two's complement representation,
1353 * in other words if it is equal to zero.
1354 *
1355 * <p>Note that this method is closely related to the logarithm base 2.
1356 * For all positive {@code int} values x:
1357 * <ul>
1358 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1359 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1360 * </ul>
1361 *
1362 * @return the number of zero bits preceding the highest-order
1363 * ("leftmost") one-bit in the two's complement binary representation
1364 * of the specified {@code int} value, or 32 if the value
1365 * is equal to zero.
1366 * @since 1.5
1367 */
1368 public static int numberOfLeadingZeros(int i) {
1369 // HD, Figure 5-6
1370 if (i == 0)
1371 return 32;
1372 int n = 1;
1373 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1374 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1375 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1376 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1377 n -= i >>> 31;
1378 return n;
1379 }
1380
1381 /**
1382 * Returns the number of zero bits following the lowest-order ("rightmost")
1383 * one-bit in the two's complement binary representation of the specified
1384 * {@code int} value. Returns 32 if the specified value has no
1385 * one-bits in its two's complement representation, in other words if it is
1386 * equal to zero.
1387 *
1388 * @return the number of zero bits following the lowest-order ("rightmost")
1389 * one-bit in the two's complement binary representation of the
1390 * specified {@code int} value, or 32 if the value is equal
1391 * to zero.
1392 * @since 1.5
1393 */
1394 public static int numberOfTrailingZeros(int i) {
1395 // HD, Figure 5-14
1396 int y;
1397 if (i == 0) return 32;
1398 int n = 31;
1399 y = i <<16; if (y != 0) { n = n -16; i = y; }
1400 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1401 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1402 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1403 return n - ((i << 1) >>> 31);
1404 }
1405
1406 /**
1407 * Returns the number of one-bits in the two's complement binary
1408 * representation of the specified {@code int} value. This function is
1409 * sometimes referred to as the <i>population count</i>.
1410 *
1411 * @return the number of one-bits in the two's complement binary
1412 * representation of the specified {@code int} value.
1413 * @since 1.5
1414 */
1415 public static int bitCount(int i) {
1416 // HD, Figure 5-2
1417 i = i - ((i >>> 1) & 0x55555555);
1418 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1419 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1420 i = i + (i >>> 8);
1421 i = i + (i >>> 16);
1422 return i & 0x3f;
1423 }
1424
1425 /**
1426 * Returns the value obtained by rotating the two's complement binary
1427 * representation of the specified {@code int} value left by the
1428 * specified number of bits. (Bits shifted out of the left hand, or
1429 * high-order, side reenter on the right, or low-order.)
1430 *
1431 * <p>Note that left rotation with a negative distance is equivalent to
1432 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1433 * distance)}. Note also that rotation by any multiple of 32 is a
1434 * no-op, so all but the last five bits of the rotation distance can be
1435 * ignored, even if the distance is negative: {@code rotateLeft(val,
1436 * distance) == rotateLeft(val, distance & 0x1F)}.
1437 *
1438 * @return the value obtained by rotating the two's complement binary
1439 * representation of the specified {@code int} value left by the
1440 * specified number of bits.
1441 * @since 1.5
1442 */
1443 public static int rotateLeft(int i, int distance) {
1444 return (i << distance) | (i >>> -distance);
1445 }
1446
1447 /**
1448 * Returns the value obtained by rotating the two's complement binary
1449 * representation of the specified {@code int} value right by the
1450 * specified number of bits. (Bits shifted out of the right hand, or
1451 * low-order, side reenter on the left, or high-order.)
1452 *
1453 * <p>Note that right rotation with a negative distance is equivalent to
1454 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1455 * distance)}. Note also that rotation by any multiple of 32 is a
1456 * no-op, so all but the last five bits of the rotation distance can be
1457 * ignored, even if the distance is negative: {@code rotateRight(val,
1458 * distance) == rotateRight(val, distance & 0x1F)}.
1459 *
1460 * @return the value obtained by rotating the two's complement binary
1461 * representation of the specified {@code int} value right by the
1462 * specified number of bits.
1463 * @since 1.5
1464 */
1465 public static int rotateRight(int i, int distance) {
1466 return (i >>> distance) | (i << -distance);
1467 }
1468
1469 /**
1470 * Returns the value obtained by reversing the order of the bits in the
1471 * two's complement binary representation of the specified {@code int}
1472 * value.
1473 *
1474 * @return the value obtained by reversing order of the bits in the
1475 * specified {@code int} value.
1476 * @since 1.5
1477 */
1478 public static int reverse(int i) {
1479 // HD, Figure 7-1
1480 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1481 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1482 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1483 i = (i << 24) | ((i & 0xff00) << 8) |
1484 ((i >>> 8) & 0xff00) | (i >>> 24);
1485 return i;
1486 }
1487
1488 /**
1489 * Returns the signum function of the specified {@code int} value. (The
1490 * return value is -1 if the specified value is negative; 0 if the
1491 * specified value is zero; and 1 if the specified value is positive.)
1492 *
1493 * @return the signum function of the specified {@code int} value.
1494 * @since 1.5
1495 */
1496 public static int signum(int i) {
1497 // HD, Section 2-7
1498 return (i >> 31) | (-i >>> 31);
1499 }
1500
1501 /**
1502 * Returns the value obtained by reversing the order of the bytes in the
1503 * two's complement representation of the specified {@code int} value.
1504 *
1505 * @return the value obtained by reversing the bytes in the specified
1506 * {@code int} value.
1507 * @since 1.5
1508 */
1509 public static int reverseBytes(int i) {
1510 return ((i >>> 24) ) |
1511 ((i >> 8) & 0xFF00) |
1512 ((i << 8) & 0xFF0000) |
1513 ((i << 24));
1514 }
1515
1516 /**
1517 * Adds two integers together as per the + operator.
1518 *
1519 * @param a the first operand
1520 * @param b the second operand
1521 * @return the sum of {@code a} and {@code b}
1522 * @see java.util.function.BinaryOperator
1523 * @since 1.8
1524 */
1525 public static int sum(int a, int b) {
1526 return a + b;
1527 }
1528
1529 /**
1530 * Returns the greater of two {@code int} values
1531 * as if by calling {@link Math#max(int, int) Math.max}.
1532 *
1533 * @param a the first operand
1534 * @param b the second operand
1535 * @return the greater of {@code a} and {@code b}
1536 * @see java.util.function.BinaryOperator
1537 * @since 1.8
1538 */
1539 public static int max(int a, int b) {
1540 return Math.max(a, b);
1541 }
1542
1543 /**
1544 * Returns the smaller of two {@code int} values
1545 * as if by calling {@link Math#min(int, int) Math.min}.
1546 *
1547 * @param a the first operand
1548 * @param b the second operand
1549 * @return the smaller of {@code a} and {@code b}
1550 * @see java.util.function.BinaryOperator
1551 * @since 1.8
1552 */
1553 public static int min(int a, int b) {
1554 return Math.min(a, b);
1555 }
1556
1557 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1558 @Native private static final long serialVersionUID = 1360826667806852920L;
1559 }