1 /*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import java.lang.annotation.Native;
29
30 /**
31 * The {@code Integer} class wraps a value of the primitive type
32 * {@code int} in an object. An object of type {@code Integer}
33 * contains a single field whose type is {@code int}.
34 *
35 * <p>In addition, this class provides several methods for converting
36 * an {@code int} to a {@code String} and a {@code String} to an
37 * {@code int}, as well as other constants and methods useful when
38 * dealing with an {@code int}.
39 *
40 * <p>Implementation note: The implementations of the "bit twiddling"
41 * methods (such as {@link #highestOneBit(int) highestOneBit} and
42 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
43 * based on material from Henry S. Warren, Jr.'s <i>Hacker's
44 * Delight</i>, (Addison Wesley, 2002).
45 *
46 * @author Lee Boynton
47 * @author Arthur van Hoff
48 * @author Josh Bloch
49 * @author Joseph D. Darcy
50 * @since JDK1.0
51 */
52 public final class Integer extends Number implements Comparable<Integer> {
53 /**
54 * A constant holding the minimum value an {@code int} can
55 * have, -2<sup>31</sup>.
56 */
57 @Native public static final int MIN_VALUE = 0x80000000;
58
59 /**
60 * A constant holding the maximum value an {@code int} can
61 * have, 2<sup>31</sup>-1.
62 */
63 @Native public static final int MAX_VALUE = 0x7fffffff;
64
65 /**
66 * The {@code Class} instance representing the primitive type
67 * {@code int}.
68 *
69 * @since JDK1.1
70 */
71 @SuppressWarnings("unchecked")
72 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
73
74 /**
75 * All possible chars for representing a number as a String
76 */
77 final static char[] digits = {
78 '0' , '1' , '2' , '3' , '4' , '5' ,
79 '6' , '7' , '8' , '9' , 'a' , 'b' ,
80 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
81 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
82 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
83 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
84 };
85
86 /**
87 * Returns a string representation of the first argument in the
88 * radix specified by the second argument.
89 *
90 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
91 * or larger than {@code Character.MAX_RADIX}, then the radix
92 * {@code 10} is used instead.
93 *
94 * <p>If the first argument is negative, the first element of the
95 * result is the ASCII minus character {@code '-'}
96 * ({@code '\u005Cu002D'}). If the first argument is not
97 * negative, no sign character appears in the result.
98 *
99 * <p>The remaining characters of the result represent the magnitude
100 * of the first argument. If the magnitude is zero, it is
101 * represented by a single zero character {@code '0'}
102 * ({@code '\u005Cu0030'}); otherwise, the first character of
103 * the representation of the magnitude will not be the zero
104 * character. The following ASCII characters are used as digits:
105 *
106 * <blockquote>
107 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
108 * </blockquote>
109 *
110 * These are {@code '\u005Cu0030'} through
111 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
112 * {@code '\u005Cu007A'}. If {@code radix} is
113 * <var>N</var>, then the first <var>N</var> of these characters
114 * are used as radix-<var>N</var> digits in the order shown. Thus,
115 * the digits for hexadecimal (radix 16) are
116 * {@code 0123456789abcdef}. If uppercase letters are
117 * desired, the {@link java.lang.String#toUpperCase()} method may
118 * be called on the result:
119 *
120 * <blockquote>
121 * {@code Integer.toString(n, 16).toUpperCase()}
122 * </blockquote>
123 *
124 * @param i an integer to be converted to a string.
125 * @param radix the radix to use in the string representation.
126 * @return a string representation of the argument in the specified radix.
127 * @see java.lang.Character#MAX_RADIX
128 * @see java.lang.Character#MIN_RADIX
129 */
130 public static String toString(int i, int radix) {
131 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
132 radix = 10;
133
134 /* Use the faster version */
135 if (radix == 10) {
136 return toString(i);
137 }
138
139 char buf[] = new char[33];
140 boolean negative = (i < 0);
141 int charPos = 32;
142
143 if (!negative) {
144 i = -i;
145 }
146
147 while (i <= -radix) {
148 buf[charPos--] = digits[-(i % radix)];
149 i = i / radix;
150 }
151 buf[charPos] = digits[-i];
152
153 if (negative) {
154 buf[--charPos] = '-';
155 }
156
157 return new String(buf, charPos, (33 - charPos));
158 }
159
160 /**
161 * Returns a string representation of the first argument as an
162 * unsigned integer value in the radix specified by the second
163 * argument.
164 *
165 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
166 * or larger than {@code Character.MAX_RADIX}, then the radix
167 * {@code 10} is used instead.
168 *
169 * <p>Note that since the first argument is treated as an unsigned
170 * value, no leading sign character is printed.
171 *
172 * <p>If the magnitude is zero, it is represented by a single zero
173 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
174 * the first character of the representation of the magnitude will
175 * not be the zero character.
176 *
177 * <p>The behavior of radixes and the characters used as digits
178 * are the same as {@link #toString(int, int) toString}.
179 *
180 * @param i an integer to be converted to an unsigned string.
181 * @param radix the radix to use in the string representation.
182 * @return an unsigned string representation of the argument in the specified radix.
183 * @see #toString(int, int)
184 * @since 1.8
185 */
186 public static String toUnsignedString(int i, int radix) {
187 return Long.toUnsignedString(toUnsignedLong(i), radix);
188 }
189
190 /**
191 * Returns a string representation of the integer argument as an
192 * unsigned integer in base 16.
193 *
194 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
195 * if the argument is negative; otherwise, it is equal to the
196 * argument. This value is converted to a string of ASCII digits
197 * in hexadecimal (base 16) with no extra leading
198 * {@code 0}s.
199 *
200 * <p>The value of the argument can be recovered from the returned
201 * string {@code s} by calling {@link
202 * Integer#parseUnsignedInt(String, int)
203 * Integer.parseUnsignedInt(s, 16)}.
204 *
205 * <p>If the unsigned magnitude is zero, it is represented by a
206 * single zero character {@code '0'} ({@code '\u005Cu0030'});
207 * otherwise, the first character of the representation of the
208 * unsigned magnitude will not be the zero character. The
209 * following characters are used as hexadecimal digits:
210 *
211 * <blockquote>
212 * {@code 0123456789abcdef}
213 * </blockquote>
214 *
215 * These are the characters {@code '\u005Cu0030'} through
216 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
217 * {@code '\u005Cu0066'}. If uppercase letters are
218 * desired, the {@link java.lang.String#toUpperCase()} method may
219 * be called on the result:
220 *
221 * <blockquote>
222 * {@code Integer.toHexString(n).toUpperCase()}
223 * </blockquote>
224 *
225 * @param i an integer to be converted to a string.
226 * @return the string representation of the unsigned integer value
227 * represented by the argument in hexadecimal (base 16).
228 * @see #parseUnsignedInt(String, int)
229 * @see #toUnsignedString(int, int)
230 * @since JDK1.0.2
231 */
232 public static String toHexString(int i) {
233 return toUnsignedString0(i, 4);
234 }
235
236 /**
237 * Returns a string representation of the integer argument as an
238 * unsigned integer in base 8.
239 *
240 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
241 * if the argument is negative; otherwise, it is equal to the
242 * argument. This value is converted to a string of ASCII digits
243 * in octal (base 8) with no extra leading {@code 0}s.
244 *
245 * <p>The value of the argument can be recovered from the returned
246 * string {@code s} by calling {@link
247 * Integer#parseUnsignedInt(String, int)
248 * Integer.parseUnsignedInt(s, 8)}.
249 *
250 * <p>If the unsigned magnitude is zero, it is represented by a
251 * single zero character {@code '0'} ({@code '\u005Cu0030'});
252 * otherwise, the first character of the representation of the
253 * unsigned magnitude will not be the zero character. The
254 * following characters are used as octal digits:
255 *
256 * <blockquote>
257 * {@code 01234567}
258 * </blockquote>
259 *
260 * These are the characters {@code '\u005Cu0030'} through
261 * {@code '\u005Cu0037'}.
262 *
263 * @param i an integer to be converted to a string.
264 * @return the string representation of the unsigned integer value
265 * represented by the argument in octal (base 8).
266 * @see #parseUnsignedInt(String, int)
267 * @see #toUnsignedString(int, int)
268 * @since JDK1.0.2
269 */
270 public static String toOctalString(int i) {
271 return toUnsignedString0(i, 3);
272 }
273
274 /**
275 * Returns a string representation of the integer argument as an
276 * unsigned integer in base 2.
277 *
278 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
279 * if the argument is negative; otherwise it is equal to the
280 * argument. This value is converted to a string of ASCII digits
281 * in binary (base 2) with no extra leading {@code 0}s.
282 *
283 * <p>The value of the argument can be recovered from the returned
284 * string {@code s} by calling {@link
285 * Integer#parseUnsignedInt(String, int)
286 * Integer.parseUnsignedInt(s, 2)}.
287 *
288 * <p>If the unsigned magnitude is zero, it is represented by a
289 * single zero character {@code '0'} ({@code '\u005Cu0030'});
290 * otherwise, the first character of the representation of the
291 * unsigned magnitude will not be the zero character. The
292 * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
293 * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
294 *
295 * @param i an integer to be converted to a string.
296 * @return the string representation of the unsigned integer value
297 * represented by the argument in binary (base 2).
298 * @see #parseUnsignedInt(String, int)
299 * @see #toUnsignedString(int, int)
300 * @since JDK1.0.2
301 */
302 public static String toBinaryString(int i) {
303 return toUnsignedString0(i, 1);
304 }
305
306 /**
307 * Convert the integer to an unsigned number.
308 */
309 private static String toUnsignedString0(int val, int shift) {
310 // assert shift > 0 && shift <=5 : "Illegal shift value";
311 int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
312 int chars = Math.max(((mag + (shift - 1)) / shift), 1);
313 char[] buf = new char[chars];
314
315 formatUnsignedInt(val, shift, buf, 0, chars);
316
317 // Use special constructor which takes over "buf".
318 return new String(buf, true);
319 }
320
321 /**
322 * Format an {@code int} (treated as unsigned) into a character buffer. If
323 * {@code len} exceeds the formatted ASCII representation of {@code val},
324 * {@code buf} will be padded with leading zeroes.
325 *
326 * @param val the unsigned int to format
327 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
328 * @param buf the character buffer to write to
329 * @param offset the offset in the destination buffer to start at
330 * @param len the number of characters to write
331 */
332 static void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
333 // assert shift > 0 && shift <=5 : "Illegal shift value";
334 // assert offset >= 0 && offset < buf.length : "illegal offset";
335 // assert len > 0 && (offset + len) <= buf.length : "illegal length";
336 int charPos = offset + len;
337 int radix = 1 << shift;
338 int mask = radix - 1;
339 do {
340 buf[--charPos] = Integer.digits[val & mask];
341 val >>>= shift;
342 } while (charPos > offset);
343 }
344
345 final static char [] DigitTens = {
346 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
347 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
348 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
349 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
350 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
351 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
352 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
353 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
354 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
355 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
356 } ;
357
358 final static char [] DigitOnes = {
359 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
360 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
361 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
362 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
363 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
364 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
365 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
366 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
367 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
368 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
369 } ;
370
371 // I use the "invariant division by multiplication" trick to
372 // accelerate Integer.toString. In particular we want to
373 // avoid division by 10.
374 //
375 // The "trick" has roughly the same performance characteristics
376 // as the "classic" Integer.toString code on a non-JIT VM.
377 // The trick avoids .rem and .div calls but has a longer code
378 // path and is thus dominated by dispatch overhead. In the
379 // JIT case the dispatch overhead doesn't exist and the
380 // "trick" is considerably faster than the classic code.
381 //
382 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
383 // sequence.
384 //
385 // RE: Division by Invariant Integers using Multiplication
386 // T Gralund, P Montgomery
387 // ACM PLDI 1994
388 //
389
390 /**
391 * Returns a {@code String} object representing the
392 * specified integer. The argument is converted to signed decimal
393 * representation and returned as a string, exactly as if the
394 * argument and radix 10 were given as arguments to the {@link
395 * #toString(int, int)} method.
396 *
397 * @param i an integer to be converted.
398 * @return a string representation of the argument in base 10.
399 */
400 public static String toString(int i) {
401 if (i == Integer.MIN_VALUE)
402 return "-2147483648";
403 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
404 char[] buf = new char[size];
405 getChars(i, size, buf);
406 return new String(buf, true);
407 }
408
409 /**
410 * Returns a string representation of the argument as an unsigned
411 * decimal value.
412 *
413 * The argument is converted to unsigned decimal representation
414 * and returned as a string exactly as if the argument and radix
415 * 10 were given as arguments to the {@link #toUnsignedString(int,
416 * int)} method.
417 *
418 * @param i an integer to be converted to an unsigned string.
419 * @return an unsigned string representation of the argument.
420 * @see #toUnsignedString(int, int)
421 * @since 1.8
422 */
423 public static String toUnsignedString(int i) {
424 return Long.toString(toUnsignedLong(i));
425 }
426
427 /**
428 * Places characters representing the integer i into the
429 * character array buf. The characters are placed into
430 * the buffer backwards starting with the least significant
431 * digit at the specified index (exclusive), and working
432 * backwards from there.
433 *
434 * Will fail if i == Integer.MIN_VALUE
435 */
436 static void getChars(int i, int index, char[] buf) {
437 int q, r;
438 int charPos = index;
439 char sign = 0;
440
441 if (i < 0) {
442 sign = '-';
443 i = -i;
444 }
445
446 // Generate two digits per iteration
447 while (i >= 65536) {
448 q = i / 100;
449 // really: r = i - (q * 100);
450 r = i - ((q << 6) + (q << 5) + (q << 2));
451 i = q;
452 buf [--charPos] = DigitOnes[r];
453 buf [--charPos] = DigitTens[r];
454 }
455
456 // Fall thru to fast mode for smaller numbers
457 // assert(i <= 65536, i);
458 for (;;) {
459 q = (i * 52429) >>> (16+3);
460 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
461 buf [--charPos] = digits [r];
462 i = q;
463 if (i == 0) break;
464 }
465 if (sign != 0) {
466 buf [--charPos] = sign;
467 }
468 }
469
470 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
471 99999999, 999999999, Integer.MAX_VALUE };
472
473 // Requires positive x
474 static int stringSize(int x) {
475 for (int i=0; ; i++)
476 if (x <= sizeTable[i])
477 return i+1;
478 }
479
480 /**
481 * Parses the string argument as a signed integer in the radix
482 * specified by the second argument. The characters in the string
483 * must all be digits of the specified radix (as determined by
484 * whether {@link java.lang.Character#digit(char, int)} returns a
485 * nonnegative value), except that the first character may be an
486 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
487 * indicate a negative value or an ASCII plus sign {@code '+'}
488 * ({@code '\u005Cu002B'}) to indicate a positive value. The
489 * resulting integer value is returned.
490 *
491 * <p>An exception of type {@code NumberFormatException} is
492 * thrown if any of the following situations occurs:
493 * <ul>
494 * <li>The first argument is {@code null} or is a string of
495 * length zero.
496 *
497 * <li>The radix is either smaller than
498 * {@link java.lang.Character#MIN_RADIX} or
499 * larger than {@link java.lang.Character#MAX_RADIX}.
500 *
501 * <li>Any character of the string is not a digit of the specified
502 * radix, except that the first character may be a minus sign
503 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
504 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
505 * string is longer than length 1.
506 *
507 * <li>The value represented by the string is not a value of type
508 * {@code int}.
509 * </ul>
510 *
511 * <p>Examples:
512 * <blockquote><pre>
513 * parseInt("0", 10) returns 0
514 * parseInt("473", 10) returns 473
515 * parseInt("+42", 10) returns 42
516 * parseInt("-0", 10) returns 0
517 * parseInt("-FF", 16) returns -255
518 * parseInt("1100110", 2) returns 102
519 * parseInt("2147483647", 10) returns 2147483647
520 * parseInt("-2147483648", 10) returns -2147483648
521 * parseInt("2147483648", 10) throws a NumberFormatException
522 * parseInt("99", 8) throws a NumberFormatException
523 * parseInt("Kona", 10) throws a NumberFormatException
524 * parseInt("Kona", 27) returns 411787
525 * </pre></blockquote>
526 *
527 * @param s the {@code String} containing the integer
528 * representation to be parsed
529 * @param radix the radix to be used while parsing {@code s}.
530 * @return the integer represented by the string argument in the
531 * specified radix.
532 * @exception NumberFormatException if the {@code String}
533 * does not contain a parsable {@code int}.
534 */
535 public static int parseInt(String s, int radix)
536 throws NumberFormatException
537 {
538 /*
539 * WARNING: This method may be invoked early during VM initialization
540 * before IntegerCache is initialized. Care must be taken to not use
541 * the valueOf method.
542 */
543
544 if (s == null) {
545 throw new NumberFormatException("null");
546 }
547
548 if (radix < Character.MIN_RADIX) {
549 throw new NumberFormatException("radix " + radix +
550 " less than Character.MIN_RADIX");
551 }
552
553 if (radix > Character.MAX_RADIX) {
554 throw new NumberFormatException("radix " + radix +
555 " greater than Character.MAX_RADIX");
556 }
557
558 int result = 0;
559 boolean negative = false;
560 int i = 0, len = s.length();
561 int limit = -Integer.MAX_VALUE;
562 int multmin;
563 int digit;
564
565 if (len > 0) {
566 char firstChar = s.charAt(0);
567 if (firstChar < '0') { // Possible leading "+" or "-"
568 if (firstChar == '-') {
569 negative = true;
570 limit = Integer.MIN_VALUE;
571 } else if (firstChar != '+')
572 throw NumberFormatException.forInputString(s);
573
574 if (len == 1) // Cannot have lone "+" or "-"
575 throw NumberFormatException.forInputString(s);
576 i++;
577 }
578 multmin = limit / radix;
579 while (i < len) {
580 // Accumulating negatively avoids surprises near MAX_VALUE
581 digit = Character.digit(s.charAt(i++),radix);
582 if (digit < 0) {
583 throw NumberFormatException.forInputString(s);
584 }
585 if (result < multmin) {
586 throw NumberFormatException.forInputString(s);
587 }
588 result *= radix;
589 if (result < limit + digit) {
590 throw NumberFormatException.forInputString(s);
591 }
592 result -= digit;
593 }
594 } else {
595 throw NumberFormatException.forInputString(s);
596 }
597 return negative ? result : -result;
598 }
599
600 /**
601 * Parses the string argument as a signed decimal integer. The
602 * characters in the string must all be decimal digits, except
603 * that the first character may be an ASCII minus sign {@code '-'}
604 * ({@code '\u005Cu002D'}) to indicate a negative value or an
605 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
606 * indicate a positive value. The resulting integer value is
607 * returned, exactly as if the argument and the radix 10 were
608 * given as arguments to the {@link #parseInt(java.lang.String,
609 * int)} method.
610 *
611 * @param s a {@code String} containing the {@code int}
612 * representation to be parsed
613 * @return the integer value represented by the argument in decimal.
614 * @exception NumberFormatException if the string does not contain a
615 * parsable integer.
616 */
617 public static int parseInt(String s) throws NumberFormatException {
618 return parseInt(s,10);
619 }
620
621 /**
622 * Parses the string argument as an unsigned integer in the radix
623 * specified by the second argument. An unsigned integer maps the
624 * values usually associated with negative numbers to positive
625 * numbers larger than {@code MAX_VALUE}.
626 *
627 * The characters in the string must all be digits of the
628 * specified radix (as determined by whether {@link
629 * java.lang.Character#digit(char, int)} returns a nonnegative
630 * value), except that the first character may be an ASCII plus
631 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
632 * integer value is returned.
633 *
634 * <p>An exception of type {@code NumberFormatException} is
635 * thrown if any of the following situations occurs:
636 * <ul>
637 * <li>The first argument is {@code null} or is a string of
638 * length zero.
639 *
640 * <li>The radix is either smaller than
641 * {@link java.lang.Character#MIN_RADIX} or
642 * larger than {@link java.lang.Character#MAX_RADIX}.
643 *
644 * <li>Any character of the string is not a digit of the specified
645 * radix, except that the first character may be a plus sign
646 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
647 * string is longer than length 1.
648 *
649 * <li>The value represented by the string is larger than the
650 * largest unsigned {@code int}, 2<sup>32</sup>-1.
651 *
652 * </ul>
653 *
654 *
655 * @param s the {@code String} containing the unsigned integer
656 * representation to be parsed
657 * @param radix the radix to be used while parsing {@code s}.
658 * @return the integer represented by the string argument in the
659 * specified radix.
660 * @throws NumberFormatException if the {@code String}
661 * does not contain a parsable {@code int}.
662 * @since 1.8
663 */
664 public static int parseUnsignedInt(String s, int radix)
665 throws NumberFormatException {
666 if (s == null) {
667 throw new NumberFormatException("null");
668 }
669
670 int len = s.length();
671 if (len > 0) {
672 char firstChar = s.charAt(0);
673 if (firstChar == '-') {
674 throw new
675 NumberFormatException(String.format("Illegal leading minus sign " +
676 "on unsigned string %s.", s));
677 } else {
678 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
679 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
680 return parseInt(s, radix);
681 } else {
682 long ell = Long.parseLong(s, radix);
683 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
684 return (int) ell;
685 } else {
686 throw new
687 NumberFormatException(String.format("String value %s exceeds " +
688 "range of unsigned int.", s));
689 }
690 }
691 }
692 } else {
693 throw NumberFormatException.forInputString(s);
694 }
695 }
696
697 /**
698 * Parses the string argument as an unsigned decimal integer. The
699 * characters in the string must all be decimal digits, except
700 * that the first character may be an an ASCII plus sign {@code
701 * '+'} ({@code '\u005Cu002B'}). The resulting integer value
702 * is returned, exactly as if the argument and the radix 10 were
703 * given as arguments to the {@link
704 * #parseUnsignedInt(java.lang.String, int)} method.
705 *
706 * @param s a {@code String} containing the unsigned {@code int}
707 * representation to be parsed
708 * @return the unsigned integer value represented by the argument in decimal.
709 * @throws NumberFormatException if the string does not contain a
710 * parsable unsigned integer.
711 * @since 1.8
712 */
713 public static int parseUnsignedInt(String s) throws NumberFormatException {
714 return parseUnsignedInt(s, 10);
715 }
716
717 /**
718 * Returns an {@code Integer} object holding the value
719 * extracted from the specified {@code String} when parsed
720 * with the radix given by the second argument. The first argument
721 * is interpreted as representing a signed integer in the radix
722 * specified by the second argument, exactly as if the arguments
723 * were given to the {@link #parseInt(java.lang.String, int)}
724 * method. The result is an {@code Integer} object that
725 * represents the integer value specified by the string.
726 *
727 * <p>In other words, this method returns an {@code Integer}
728 * object equal to the value of:
729 *
730 * <blockquote>
731 * {@code new Integer(Integer.parseInt(s, radix))}
732 * </blockquote>
733 *
734 * @param s the string to be parsed.
735 * @param radix the radix to be used in interpreting {@code s}
736 * @return an {@code Integer} object holding the value
737 * represented by the string argument in the specified
738 * radix.
739 * @exception NumberFormatException if the {@code String}
740 * does not contain a parsable {@code int}.
741 */
742 public static Integer valueOf(String s, int radix) throws NumberFormatException {
743 return Integer.valueOf(parseInt(s,radix));
744 }
745
746 /**
747 * Returns an {@code Integer} object holding the
748 * value of the specified {@code String}. The argument is
749 * interpreted as representing a signed decimal integer, exactly
750 * as if the argument were given to the {@link
751 * #parseInt(java.lang.String)} method. The result is an
752 * {@code Integer} object that represents the integer value
753 * specified by the string.
754 *
755 * <p>In other words, this method returns an {@code Integer}
756 * object equal to the value of:
757 *
758 * <blockquote>
759 * {@code new Integer(Integer.parseInt(s))}
760 * </blockquote>
761 *
762 * @param s the string to be parsed.
763 * @return an {@code Integer} object holding the value
764 * represented by the string argument.
765 * @exception NumberFormatException if the string cannot be parsed
766 * as an integer.
767 */
768 public static Integer valueOf(String s) throws NumberFormatException {
769 return Integer.valueOf(parseInt(s, 10));
770 }
771
772 /**
773 * Cache to support the object identity semantics of autoboxing for values between
774 * -128 and 127 (inclusive) as required by JLS.
775 *
776 * The cache is initialized on first usage. The size of the cache
777 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
778 * During VM initialization, java.lang.Integer.IntegerCache.high property
779 * may be set and saved in the private system properties in the
780 * sun.misc.VM class.
781 */
782
783 private static class IntegerCache {
784 static final int low = -128;
785 static final int high;
786 static final Integer cache[];
787
788 static {
789 // high value may be configured by property
790 int h = 127;
791 String integerCacheHighPropValue =
792 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
793 if (integerCacheHighPropValue != null) {
794 try {
795 int i = parseInt(integerCacheHighPropValue);
796 i = Math.max(i, 127);
797 // Maximum array size is Integer.MAX_VALUE
798 h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
799 } catch( NumberFormatException nfe) {
800 // If the property cannot be parsed into an int, ignore it.
801 }
802 }
803 high = h;
804
805 cache = new Integer[(high - low) + 1];
806 int j = low;
807 for(int k = 0; k < cache.length; k++)
808 cache[k] = new Integer(j++);
809
810 // range [-128, 127] must be interned (JLS7 5.1.7)
811 assert IntegerCache.high >= 127;
812 }
813
814 private IntegerCache() {}
815 }
816
817 /**
818 * Returns an {@code Integer} instance representing the specified
819 * {@code int} value. If a new {@code Integer} instance is not
820 * required, this method should generally be used in preference to
821 * the constructor {@link #Integer(int)}, as this method is likely
822 * to yield significantly better space and time performance by
823 * caching frequently requested values.
824 *
825 * This method will always cache values in the range -128 to 127,
826 * inclusive, and may cache other values outside of this range.
827 *
828 * @param i an {@code int} value.
829 * @return an {@code Integer} instance representing {@code i}.
830 * @since 1.5
831 */
832 public static Integer valueOf(int i) {
833 if (i >= IntegerCache.low && i <= IntegerCache.high)
834 return IntegerCache.cache[i + (-IntegerCache.low)];
835 return new Integer(i);
836 }
837
838 /**
839 * The value of the {@code Integer}.
840 *
841 * @serial
842 */
843 private final int value;
844
845 /**
846 * Constructs a newly allocated {@code Integer} object that
847 * represents the specified {@code int} value.
848 *
849 * @param value the value to be represented by the
850 * {@code Integer} object.
851 */
852 public Integer(int value) {
853 this.value = value;
854 }
855
856 /**
857 * Constructs a newly allocated {@code Integer} object that
858 * represents the {@code int} value indicated by the
859 * {@code String} parameter. The string is converted to an
860 * {@code int} value in exactly the manner used by the
861 * {@code parseInt} method for radix 10.
862 *
863 * @param s the {@code String} to be converted to an
864 * {@code Integer}.
865 * @exception NumberFormatException if the {@code String} does not
866 * contain a parsable integer.
867 * @see java.lang.Integer#parseInt(java.lang.String, int)
868 */
869 public Integer(String s) throws NumberFormatException {
870 this.value = parseInt(s, 10);
871 }
872
873 /**
874 * Returns the value of this {@code Integer} as a {@code byte}
875 * after a narrowing primitive conversion.
876 * @jls 5.1.3 Narrowing Primitive Conversions
877 */
878 public byte byteValue() {
879 return (byte)value;
880 }
881
882 /**
883 * Returns the value of this {@code Integer} as a {@code short}
884 * after a narrowing primitive conversion.
885 * @jls 5.1.3 Narrowing Primitive Conversions
886 */
887 public short shortValue() {
888 return (short)value;
889 }
890
891 /**
892 * Returns the value of this {@code Integer} as an
893 * {@code int}.
894 */
895 public int intValue() {
896 return value;
897 }
898
899 /**
900 * Returns the value of this {@code Integer} as a {@code long}
901 * after a widening primitive conversion.
902 * @jls 5.1.2 Widening Primitive Conversions
903 * @see Integer#toUnsignedLong(int)
904 */
905 public long longValue() {
906 return (long)value;
907 }
908
909 /**
910 * Returns the value of this {@code Integer} as a {@code float}
911 * after a widening primitive conversion.
912 * @jls 5.1.2 Widening Primitive Conversions
913 */
914 public float floatValue() {
915 return (float)value;
916 }
917
918 /**
919 * Returns the value of this {@code Integer} as a {@code double}
920 * after a widening primitive conversion.
921 * @jls 5.1.2 Widening Primitive Conversions
922 */
923 public double doubleValue() {
924 return (double)value;
925 }
926
927 /**
928 * Returns a {@code String} object representing this
929 * {@code Integer}'s value. The value is converted to signed
930 * decimal representation and returned as a string, exactly as if
931 * the integer value were given as an argument to the {@link
932 * java.lang.Integer#toString(int)} method.
933 *
934 * @return a string representation of the value of this object in
935 * base 10.
936 */
937 public String toString() {
938 return toString(value);
939 }
940
941 /**
942 * Returns a hash code for this {@code Integer}.
943 *
944 * @return a hash code value for this object, equal to the
945 * primitive {@code int} value represented by this
946 * {@code Integer} object.
947 */
948 @Override
949 public int hashCode() {
950 return Integer.hashCode(value);
951 }
952
953 /**
954 * Returns a hash code for a {@code int} value; compatible with
955 * {@code Integer.hashCode()}.
956 *
957 * @param value the value to hash
958 * @since 1.8
959 *
960 * @return a hash code value for a {@code int} value.
961 */
962 public static int hashCode(int value) {
963 return value;
964 }
965
966 /**
967 * Compares this object to the specified object. The result is
968 * {@code true} if and only if the argument is not
969 * {@code null} and is an {@code Integer} object that
970 * contains the same {@code int} value as this object.
971 *
972 * @param obj the object to compare with.
973 * @return {@code true} if the objects are the same;
974 * {@code false} otherwise.
975 */
976 public boolean equals(Object obj) {
977 if (obj instanceof Integer) {
978 return value == ((Integer)obj).intValue();
979 }
980 return false;
981 }
982
983 /**
984 * Determines the integer value of the system property with the
985 * specified name.
986 *
987 * <p>The first argument is treated as the name of a system
988 * property. System properties are accessible through the {@link
989 * java.lang.System#getProperty(java.lang.String)} method. The
990 * string value of this property is then interpreted as an integer
991 * value using the grammar supported by {@link Integer#decode decode} and
992 * an {@code Integer} object representing this value is returned.
993 *
994 * <p>If there is no property with the specified name, if the
995 * specified name is empty or {@code null}, or if the property
996 * does not have the correct numeric format, then {@code null} is
997 * returned.
998 *
999 * <p>In other words, this method returns an {@code Integer}
1000 * object equal to the value of:
1001 *
1002 * <blockquote>
1003 * {@code getInteger(nm, null)}
1004 * </blockquote>
1005 *
1006 * @param nm property name.
1007 * @return the {@code Integer} value of the property.
1008 * @throws SecurityException for the same reasons as
1009 * {@link System#getProperty(String) System.getProperty}
1010 * @see java.lang.System#getProperty(java.lang.String)
1011 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1012 */
1013 public static Integer getInteger(String nm) {
1014 return getInteger(nm, null);
1015 }
1016
1017 /**
1018 * Determines the integer value of the system property with the
1019 * specified name.
1020 *
1021 * <p>The first argument is treated as the name of a system
1022 * property. System properties are accessible through the {@link
1023 * java.lang.System#getProperty(java.lang.String)} method. The
1024 * string value of this property is then interpreted as an integer
1025 * value using the grammar supported by {@link Integer#decode decode} and
1026 * an {@code Integer} object representing this value is returned.
1027 *
1028 * <p>The second argument is the default value. An {@code Integer} object
1029 * that represents the value of the second argument is returned if there
1030 * is no property of the specified name, if the property does not have
1031 * the correct numeric format, or if the specified name is empty or
1032 * {@code null}.
1033 *
1034 * <p>In other words, this method returns an {@code Integer} object
1035 * equal to the value of:
1036 *
1037 * <blockquote>
1038 * {@code getInteger(nm, new Integer(val))}
1039 * </blockquote>
1040 *
1041 * but in practice it may be implemented in a manner such as:
1042 *
1043 * <blockquote><pre>
1044 * Integer result = getInteger(nm, null);
1045 * return (result == null) ? new Integer(val) : result;
1046 * </pre></blockquote>
1047 *
1048 * to avoid the unnecessary allocation of an {@code Integer}
1049 * object when the default value is not needed.
1050 *
1051 * @param nm property name.
1052 * @param val default value.
1053 * @return the {@code Integer} value of the property.
1054 * @throws SecurityException for the same reasons as
1055 * {@link System#getProperty(String) System.getProperty}
1056 * @see java.lang.System#getProperty(java.lang.String)
1057 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1058 */
1059 public static Integer getInteger(String nm, int val) {
1060 Integer result = getInteger(nm, null);
1061 return (result == null) ? Integer.valueOf(val) : result;
1062 }
1063
1064 /**
1065 * Returns the integer value of the system property with the
1066 * specified name. The first argument is treated as the name of a
1067 * system property. System properties are accessible through the
1068 * {@link java.lang.System#getProperty(java.lang.String)} method.
1069 * The string value of this property is then interpreted as an
1070 * integer value, as per the {@link Integer#decode decode} method,
1071 * and an {@code Integer} object representing this value is
1072 * returned; in summary:
1073 *
1074 * <ul><li>If the property value begins with the two ASCII characters
1075 * {@code 0x} or the ASCII character {@code #}, not
1076 * followed by a minus sign, then the rest of it is parsed as a
1077 * hexadecimal integer exactly as by the method
1078 * {@link #valueOf(java.lang.String, int)} with radix 16.
1079 * <li>If the property value begins with the ASCII character
1080 * {@code 0} followed by another character, it is parsed as an
1081 * octal integer exactly as by the method
1082 * {@link #valueOf(java.lang.String, int)} with radix 8.
1083 * <li>Otherwise, the property value is parsed as a decimal integer
1084 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1085 * with radix 10.
1086 * </ul>
1087 *
1088 * <p>The second argument is the default value. The default value is
1089 * returned if there is no property of the specified name, if the
1090 * property does not have the correct numeric format, or if the
1091 * specified name is empty or {@code null}.
1092 *
1093 * @param nm property name.
1094 * @param val default value.
1095 * @return the {@code Integer} value of the property.
1096 * @throws SecurityException for the same reasons as
1097 * {@link System#getProperty(String) System.getProperty}
1098 * @see System#getProperty(java.lang.String)
1099 * @see System#getProperty(java.lang.String, java.lang.String)
1100 */
1101 public static Integer getInteger(String nm, Integer val) {
1102 String v = null;
1103 try {
1104 v = System.getProperty(nm);
1105 } catch (IllegalArgumentException | NullPointerException e) {
1106 }
1107 if (v != null) {
1108 try {
1109 return Integer.decode(v);
1110 } catch (NumberFormatException e) {
1111 }
1112 }
1113 return val;
1114 }
1115
1116 /**
1117 * Decodes a {@code String} into an {@code Integer}.
1118 * Accepts decimal, hexadecimal, and octal numbers given
1119 * by the following grammar:
1120 *
1121 * <blockquote>
1122 * <dl>
1123 * <dt><i>DecodableString:</i>
1124 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1125 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1126 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1127 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1128 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1129 *
1130 * <dt><i>Sign:</i>
1131 * <dd>{@code -}
1132 * <dd>{@code +}
1133 * </dl>
1134 * </blockquote>
1135 *
1136 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1137 * are as defined in section 3.10.1 of
1138 * <cite>The Java™ Language Specification</cite>,
1139 * except that underscores are not accepted between digits.
1140 *
1141 * <p>The sequence of characters following an optional
1142 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1143 * "{@code #}", or leading zero) is parsed as by the {@code
1144 * Integer.parseInt} method with the indicated radix (10, 16, or
1145 * 8). This sequence of characters must represent a positive
1146 * value or a {@link NumberFormatException} will be thrown. The
1147 * result is negated if first character of the specified {@code
1148 * String} is the minus sign. No whitespace characters are
1149 * permitted in the {@code String}.
1150 *
1151 * @param nm the {@code String} to decode.
1152 * @return an {@code Integer} object holding the {@code int}
1153 * value represented by {@code nm}
1154 * @exception NumberFormatException if the {@code String} does not
1155 * contain a parsable integer.
1156 * @see java.lang.Integer#parseInt(java.lang.String, int)
1157 */
1158 public static Integer decode(String nm) throws NumberFormatException {
1159 int radix = 10;
1160 int index = 0;
1161 boolean negative = false;
1162 Integer result;
1163
1164 if (nm.length() == 0)
1165 throw new NumberFormatException("Zero length string");
1166 char firstChar = nm.charAt(0);
1167 // Handle sign, if present
1168 if (firstChar == '-') {
1169 negative = true;
1170 index++;
1171 } else if (firstChar == '+')
1172 index++;
1173
1174 // Handle radix specifier, if present
1175 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1176 index += 2;
1177 radix = 16;
1178 }
1179 else if (nm.startsWith("#", index)) {
1180 index ++;
1181 radix = 16;
1182 }
1183 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1184 index ++;
1185 radix = 8;
1186 }
1187
1188 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1189 throw new NumberFormatException("Sign character in wrong position");
1190
1191 try {
1192 result = Integer.valueOf(nm.substring(index), radix);
1193 result = negative ? Integer.valueOf(-result.intValue()) : result;
1194 } catch (NumberFormatException e) {
1195 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1196 // handles this case, and causes any genuine format error to be
1197 // rethrown.
1198 String constant = negative ? ("-" + nm.substring(index))
1199 : nm.substring(index);
1200 result = Integer.valueOf(constant, radix);
1201 }
1202 return result;
1203 }
1204
1205 /**
1206 * Compares two {@code Integer} objects numerically.
1207 *
1208 * @param anotherInteger the {@code Integer} to be compared.
1209 * @return the value {@code 0} if this {@code Integer} is
1210 * equal to the argument {@code Integer}; a value less than
1211 * {@code 0} if this {@code Integer} is numerically less
1212 * than the argument {@code Integer}; and a value greater
1213 * than {@code 0} if this {@code Integer} is numerically
1214 * greater than the argument {@code Integer} (signed
1215 * comparison).
1216 * @since 1.2
1217 */
1218 public int compareTo(Integer anotherInteger) {
1219 return compare(this.value, anotherInteger.value);
1220 }
1221
1222 /**
1223 * Compares two {@code int} values numerically.
1224 * The value returned is identical to what would be returned by:
1225 * <pre>
1226 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1227 * </pre>
1228 *
1229 * @param x the first {@code int} to compare
1230 * @param y the second {@code int} to compare
1231 * @return the value {@code 0} if {@code x == y};
1232 * a value less than {@code 0} if {@code x < y}; and
1233 * a value greater than {@code 0} if {@code x > y}
1234 * @since 1.7
1235 */
1236 public static int compare(int x, int y) {
1237 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1238 }
1239
1240 /**
1241 * Compares two {@code int} values numerically treating the values
1242 * as unsigned.
1243 *
1244 * @param x the first {@code int} to compare
1245 * @param y the second {@code int} to compare
1246 * @return the value {@code 0} if {@code x == y}; a value less
1247 * than {@code 0} if {@code x < y} as unsigned values; and
1248 * a value greater than {@code 0} if {@code x > y} as
1249 * unsigned values
1250 * @since 1.8
1251 */
1252 public static int compareUnsigned(int x, int y) {
1253 return compare(x + MIN_VALUE, y + MIN_VALUE);
1254 }
1255
1256 /**
1257 * Converts the argument to a {@code long} by an unsigned
1258 * conversion. In an unsigned conversion to a {@code long}, the
1259 * high-order 32 bits of the {@code long} are zero and the
1260 * low-order 32 bits are equal to the bits of the integer
1261 * argument.
1262 *
1263 * Consequently, zero and positive {@code int} values are mapped
1264 * to a numerically equal {@code long} value and negative {@code
1265 * int} values are mapped to a {@code long} value equal to the
1266 * input plus 2<sup>32</sup>.
1267 *
1268 * @param x the value to convert to an unsigned {@code long}
1269 * @return the argument converted to {@code long} by an unsigned
1270 * conversion
1271 * @since 1.8
1272 */
1273 public static long toUnsignedLong(int x) {
1274 return ((long) x) & 0xffffffffL;
1275 }
1276
1277 /**
1278 * Returns the unsigned quotient of dividing the first argument by
1279 * the second where each argument and the result is interpreted as
1280 * an unsigned value.
1281 *
1282 * <p>Note that in two's complement arithmetic, the three other
1283 * basic arithmetic operations of add, subtract, and multiply are
1284 * bit-wise identical if the two operands are regarded as both
1285 * being signed or both being unsigned. Therefore separate {@code
1286 * addUnsigned}, etc. methods are not provided.
1287 *
1288 * @param dividend the value to be divided
1289 * @param divisor the value doing the dividing
1290 * @return the unsigned quotient of the first argument divided by
1291 * the second argument
1292 * @see #remainderUnsigned
1293 * @since 1.8
1294 */
1295 public static int divideUnsigned(int dividend, int divisor) {
1296 // In lieu of tricky code, for now just use long arithmetic.
1297 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1298 }
1299
1300 /**
1301 * Returns the unsigned remainder from dividing the first argument
1302 * by the second where each argument and the result is interpreted
1303 * as an unsigned value.
1304 *
1305 * @param dividend the value to be divided
1306 * @param divisor the value doing the dividing
1307 * @return the unsigned remainder of the first argument divided by
1308 * the second argument
1309 * @see #divideUnsigned
1310 * @since 1.8
1311 */
1312 public static int remainderUnsigned(int dividend, int divisor) {
1313 // In lieu of tricky code, for now just use long arithmetic.
1314 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1315 }
1316
1317
1318 // Bit twiddling
1319
1320 /**
1321 * The number of bits used to represent an {@code int} value in two's
1322 * complement binary form.
1323 *
1324 * @since 1.5
1325 */
1326 @Native public static final int SIZE = 32;
1327
1328 /**
1329 * The number of bytes used to represent a {@code int} value in two's
1330 * complement binary form.
1331 *
1332 * @since 1.8
1333 */
1334 public static final int BYTES = SIZE / Byte.SIZE;
1335
1336 /**
1337 * Returns an {@code int} value with at most a single one-bit, in the
1338 * position of the highest-order ("leftmost") one-bit in the specified
1339 * {@code int} value. Returns zero if the specified value has no
1340 * one-bits in its two's complement binary representation, that is, if it
1341 * is equal to zero.
1342 *
1343 * @param i the value whose highest one bit is to be computed
1344 * @return an {@code int} value with a single one-bit, in the position
1345 * of the highest-order one-bit in the specified value, or zero if
1346 * the specified value is itself equal to zero.
1347 * @since 1.5
1348 */
1349 public static int highestOneBit(int i) {
1350 // HD, Figure 3-1
1351 i |= (i >> 1);
1352 i |= (i >> 2);
1353 i |= (i >> 4);
1354 i |= (i >> 8);
1355 i |= (i >> 16);
1356 return i - (i >>> 1);
1357 }
1358
1359 /**
1360 * Returns an {@code int} value with at most a single one-bit, in the
1361 * position of the lowest-order ("rightmost") one-bit in the specified
1362 * {@code int} value. Returns zero if the specified value has no
1363 * one-bits in its two's complement binary representation, that is, if it
1364 * is equal to zero.
1365 *
1366 * @param i the value whose lowest one bit is to be computed
1367 * @return an {@code int} value with a single one-bit, in the position
1368 * of the lowest-order one-bit in the specified value, or zero if
1369 * the specified value is itself equal to zero.
1370 * @since 1.5
1371 */
1372 public static int lowestOneBit(int i) {
1373 // HD, Section 2-1
1374 return i & -i;
1375 }
1376
1377 /**
1378 * Returns the number of zero bits preceding the highest-order
1379 * ("leftmost") one-bit in the two's complement binary representation
1380 * of the specified {@code int} value. Returns 32 if the
1381 * specified value has no one-bits in its two's complement representation,
1382 * in other words if it is equal to zero.
1383 *
1384 * <p>Note that this method is closely related to the logarithm base 2.
1385 * For all positive {@code int} values x:
1386 * <ul>
1387 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1388 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1389 * </ul>
1390 *
1391 * @param i the value whose number of leading zeros is to be computed
1392 * @return the number of zero bits preceding the highest-order
1393 * ("leftmost") one-bit in the two's complement binary representation
1394 * of the specified {@code int} value, or 32 if the value
1395 * is equal to zero.
1396 * @since 1.5
1397 */
1398 public static int numberOfLeadingZeros(int i) {
1399 // HD, Figure 5-6
1400 if (i == 0)
1401 return 32;
1402 int n = 1;
1403 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1404 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1405 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1406 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1407 n -= i >>> 31;
1408 return n;
1409 }
1410
1411 /**
1412 * Returns the number of zero bits following the lowest-order ("rightmost")
1413 * one-bit in the two's complement binary representation of the specified
1414 * {@code int} value. Returns 32 if the specified value has no
1415 * one-bits in its two's complement representation, in other words if it is
1416 * equal to zero.
1417 *
1418 * @param i the value whose number of trailing zeros is to be computed
1419 * @return the number of zero bits following the lowest-order ("rightmost")
1420 * one-bit in the two's complement binary representation of the
1421 * specified {@code int} value, or 32 if the value is equal
1422 * to zero.
1423 * @since 1.5
1424 */
1425 public static int numberOfTrailingZeros(int i) {
1426 // HD, Figure 5-14
1427 int y;
1428 if (i == 0) return 32;
1429 int n = 31;
1430 y = i <<16; if (y != 0) { n = n -16; i = y; }
1431 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1432 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1433 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1434 return n - ((i << 1) >>> 31);
1435 }
1436
1437 /**
1438 * Returns the number of one-bits in the two's complement binary
1439 * representation of the specified {@code int} value. This function is
1440 * sometimes referred to as the <i>population count</i>.
1441 *
1442 * @param i the value whose bits are to be counted
1443 * @return the number of one-bits in the two's complement binary
1444 * representation of the specified {@code int} value.
1445 * @since 1.5
1446 */
1447 public static int bitCount(int i) {
1448 // HD, Figure 5-2
1449 i = i - ((i >>> 1) & 0x55555555);
1450 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1451 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1452 i = i + (i >>> 8);
1453 i = i + (i >>> 16);
1454 return i & 0x3f;
1455 }
1456
1457 /**
1458 * Returns the value obtained by rotating the two's complement binary
1459 * representation of the specified {@code int} value left by the
1460 * specified number of bits. (Bits shifted out of the left hand, or
1461 * high-order, side reenter on the right, or low-order.)
1462 *
1463 * <p>Note that left rotation with a negative distance is equivalent to
1464 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1465 * distance)}. Note also that rotation by any multiple of 32 is a
1466 * no-op, so all but the last five bits of the rotation distance can be
1467 * ignored, even if the distance is negative: {@code rotateLeft(val,
1468 * distance) == rotateLeft(val, distance & 0x1F)}.
1469 *
1470 * @param i the value whose bits are to be rotated left
1471 * @param distance the number of bit positions to rotate left
1472 * @return the value obtained by rotating the two's complement binary
1473 * representation of the specified {@code int} value left by the
1474 * specified number of bits.
1475 * @since 1.5
1476 */
1477 public static int rotateLeft(int i, int distance) {
1478 return (i << distance) | (i >>> -distance);
1479 }
1480
1481 /**
1482 * Returns the value obtained by rotating the two's complement binary
1483 * representation of the specified {@code int} value right by the
1484 * specified number of bits. (Bits shifted out of the right hand, or
1485 * low-order, side reenter on the left, or high-order.)
1486 *
1487 * <p>Note that right rotation with a negative distance is equivalent to
1488 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1489 * distance)}. Note also that rotation by any multiple of 32 is a
1490 * no-op, so all but the last five bits of the rotation distance can be
1491 * ignored, even if the distance is negative: {@code rotateRight(val,
1492 * distance) == rotateRight(val, distance & 0x1F)}.
1493 *
1494 * @param i the value whose bits are to be rotated right
1495 * @param distance the number of bit positions to rotate right
1496 * @return the value obtained by rotating the two's complement binary
1497 * representation of the specified {@code int} value right by the
1498 * specified number of bits.
1499 * @since 1.5
1500 */
1501 public static int rotateRight(int i, int distance) {
1502 return (i >>> distance) | (i << -distance);
1503 }
1504
1505 /**
1506 * Returns the value obtained by reversing the order of the bits in the
1507 * two's complement binary representation of the specified {@code int}
1508 * value.
1509 *
1510 * @param i the value to be reversed
1511 * @return the value obtained by reversing order of the bits in the
1512 * specified {@code int} value.
1513 * @since 1.5
1514 */
1515 public static int reverse(int i) {
1516 // HD, Figure 7-1
1517 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1518 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1519 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1520 i = (i << 24) | ((i & 0xff00) << 8) |
1521 ((i >>> 8) & 0xff00) | (i >>> 24);
1522 return i;
1523 }
1524
1525 /**
1526 * Returns the signum function of the specified {@code int} value. (The
1527 * return value is -1 if the specified value is negative; 0 if the
1528 * specified value is zero; and 1 if the specified value is positive.)
1529 *
1530 * @param i the value whose signum is to be computed
1531 * @return the signum function of the specified {@code int} value.
1532 * @since 1.5
1533 */
1534 public static int signum(int i) {
1535 // HD, Section 2-7
1536 return (i >> 31) | (-i >>> 31);
1537 }
1538
1539 /**
1540 * Returns the value obtained by reversing the order of the bytes in the
1541 * two's complement representation of the specified {@code int} value.
1542 *
1543 * @param i the value whose bytes are to be reversed
1544 * @return the value obtained by reversing the bytes in the specified
1545 * {@code int} value.
1546 * @since 1.5
1547 */
1548 public static int reverseBytes(int i) {
1549 return ((i >>> 24) ) |
1550 ((i >> 8) & 0xFF00) |
1551 ((i << 8) & 0xFF0000) |
1552 ((i << 24));
1553 }
1554
1555 /**
1556 * Adds two integers together as per the + operator.
1557 *
1558 * @param a the first operand
1559 * @param b the second operand
1560 * @return the sum of {@code a} and {@code b}
1561 * @see java.util.function.BinaryOperator
1562 * @since 1.8
1563 */
1564 public static int sum(int a, int b) {
1565 return a + b;
1566 }
1567
1568 /**
1569 * Returns the greater of two {@code int} values
1570 * as if by calling {@link Math#max(int, int) Math.max}.
1571 *
1572 * @param a the first operand
1573 * @param b the second operand
1574 * @return the greater of {@code a} and {@code b}
1575 * @see java.util.function.BinaryOperator
1576 * @since 1.8
1577 */
1578 public static int max(int a, int b) {
1579 return Math.max(a, b);
1580 }
1581
1582 /**
1583 * Returns the smaller of two {@code int} values
1584 * as if by calling {@link Math#min(int, int) Math.min}.
1585 *
1586 * @param a the first operand
1587 * @param b the second operand
1588 * @return the smaller of {@code a} and {@code b}
1589 * @see java.util.function.BinaryOperator
1590 * @since 1.8
1591 */
1592 public static int min(int a, int b) {
1593 return Math.min(a, b);
1594 }
1595
1596 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1597 @Native private static final long serialVersionUID = 1360826667806852920L;
1598 }