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