1 /*
2 * Copyright (c) 1994, 2011, 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.util.Properties;
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 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 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 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
72
73 /**
74 * All possible chars for representing a number as a String
75 */
76 final static char[] digits = {
77 '0' , '1' , '2' , '3' , '4' , '5' ,
78 '6' , '7' , '8' , '9' , 'a' , 'b' ,
79 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
80 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
81 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
82 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
83 };
84
85 /**
86 * Returns a string representation of the first argument in the
87 * radix specified by the second argument.
88 *
89 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
90 * or larger than {@code Character.MAX_RADIX}, then the radix
91 * {@code 10} is used instead.
92 *
93 * <p>If the first argument is negative, the first element of the
94 * result is the ASCII minus character {@code '-'}
95 * (<code>'\u002D'</code>). If the first argument is not
96 * negative, no sign character appears in the result.
97 *
98 * <p>The remaining characters of the result represent the magnitude
99 * of the first argument. If the magnitude is zero, it is
100 * represented by a single zero character {@code '0'}
101 * (<code>'\u0030'</code>); otherwise, the first character of
102 * the representation of the magnitude will not be the zero
103 * character. The following ASCII characters are used as digits:
104 *
105 * <blockquote>
106 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
107 * </blockquote>
108 *
109 * These are <code>'\u0030'</code> through
110 * <code>'\u0039'</code> and <code>'\u0061'</code> through
111 * <code>'\u007A'</code>. If {@code radix} is
112 * <var>N</var>, then the first <var>N</var> of these characters
113 * are used as radix-<var>N</var> digits in the order shown. Thus,
114 * the digits for hexadecimal (radix 16) are
115 * {@code 0123456789abcdef}. If uppercase letters are
116 * desired, the {@link java.lang.String#toUpperCase()} method may
117 * be called on the result:
118 *
119 * <blockquote>
120 * {@code Integer.toString(n, 16).toUpperCase()}
121 * </blockquote>
122 *
123 * @param i an integer to be converted to a string.
124 * @param radix the radix to use in the string representation.
125 * @return a string representation of the argument in the specified radix.
126 * @see java.lang.Character#MAX_RADIX
127 * @see java.lang.Character#MIN_RADIX
128 */
129 public static String toString(int i, int radix) {
130
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 integer argument as an
162 * unsigned integer in base 16.
163 *
164 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
165 * if the argument is negative; otherwise, it is equal to the
166 * argument. This value is converted to a string of ASCII digits
167 * in hexadecimal (base 16) with no extra leading
168 * {@code 0}s. If the unsigned magnitude is zero, it is
169 * represented by a single zero character {@code '0'}
170 * (<code>'\u0030'</code>); otherwise, the first character of
171 * the representation of the unsigned magnitude will not be the
172 * zero character. The following characters are used as
173 * hexadecimal digits:
174 *
175 * <blockquote>
176 * {@code 0123456789abcdef}
177 * </blockquote>
178 *
179 * These are the characters <code>'\u0030'</code> through
180 * <code>'\u0039'</code> and <code>'\u0061'</code> through
181 * <code>'\u0066'</code>. If uppercase letters are
182 * desired, the {@link java.lang.String#toUpperCase()} method may
183 * be called on the result:
184 *
185 * <blockquote>
186 * {@code Integer.toHexString(n).toUpperCase()}
187 * </blockquote>
188 *
189 * @param i an integer to be converted to a string.
190 * @return the string representation of the unsigned integer value
191 * represented by the argument in hexadecimal (base 16).
192 * @since JDK1.0.2
193 */
194 public static String toHexString(int i) {
195 return toUnsignedString(i, 4);
196 }
197
198 /**
199 * Returns a string representation of the integer argument as an
200 * unsigned integer in base 8.
201 *
202 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
203 * if the argument is negative; otherwise, it is equal to the
204 * argument. This value is converted to a string of ASCII digits
205 * in octal (base 8) with no extra leading {@code 0}s.
206 *
207 * <p>If the unsigned magnitude is zero, it is represented by a
208 * single zero character {@code '0'}
209 * (<code>'\u0030'</code>); otherwise, the first character of
210 * the representation of the unsigned magnitude will not be the
211 * zero character. The following characters are used as octal
212 * digits:
213 *
214 * <blockquote>
215 * {@code 01234567}
216 * </blockquote>
217 *
218 * These are the characters <code>'\u0030'</code> through
219 * <code>'\u0037'</code>.
220 *
221 * @param i an integer to be converted to a string.
222 * @return the string representation of the unsigned integer value
223 * represented by the argument in octal (base 8).
224 * @since JDK1.0.2
225 */
226 public static String toOctalString(int i) {
227 return toUnsignedString(i, 3);
228 }
229
230 /**
231 * Returns a string representation of the integer argument as an
232 * unsigned integer in base 2.
233 *
234 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
235 * if the argument is negative; otherwise it is equal to the
236 * argument. This value is converted to a string of ASCII digits
237 * in binary (base 2) with no extra leading {@code 0}s.
238 * If the unsigned magnitude is zero, it is represented by a
239 * single zero character {@code '0'}
240 * (<code>'\u0030'</code>); otherwise, the first character of
241 * the representation of the unsigned magnitude will not be the
242 * zero character. The characters {@code '0'}
243 * (<code>'\u0030'</code>) and {@code '1'}
244 * (<code>'\u0031'</code>) are used as binary digits.
245 *
246 * @param i an integer to be converted to a string.
247 * @return the string representation of the unsigned integer value
248 * represented by the argument in binary (base 2).
249 * @since JDK1.0.2
250 */
251 public static String toBinaryString(int i) {
252 return toUnsignedString(i, 1);
253 }
254
255 /**
256 * Convert the integer to an unsigned number.
257 */
258 private static String toUnsignedString(int i, int shift) {
259 char[] buf = new char[32];
260 int charPos = 32;
261 int radix = 1 << shift;
262 int mask = radix - 1;
263 do {
264 buf[--charPos] = digits[i & mask];
265 i >>>= shift;
266 } while (i != 0);
267
268 return new String(buf, charPos, (32 - charPos));
269 }
270
271
272 final static char [] DigitTens = {
273 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
274 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
275 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
276 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
277 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
278 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
279 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
280 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
281 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
282 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
283 } ;
284
285 final static char [] DigitOnes = {
286 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
287 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
288 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
289 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
290 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
291 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
292 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
293 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
294 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
295 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
296 } ;
297
298 // I use the "invariant division by multiplication" trick to
299 // accelerate Integer.toString. In particular we want to
300 // avoid division by 10.
301 //
302 // The "trick" has roughly the same performance characteristics
303 // as the "classic" Integer.toString code on a non-JIT VM.
304 // The trick avoids .rem and .div calls but has a longer code
305 // path and is thus dominated by dispatch overhead. In the
306 // JIT case the dispatch overhead doesn't exist and the
307 // "trick" is considerably faster than the classic code.
308 //
309 // TODO-FIXME: convert (x * 52429) into the equiv shift-add
310 // sequence.
311 //
312 // RE: Division by Invariant Integers using Multiplication
313 // T Gralund, P Montgomery
314 // ACM PLDI 1994
315 //
316
317 /**
318 * Returns a {@code String} object representing the
319 * specified integer. The argument is converted to signed decimal
320 * representation and returned as a string, exactly as if the
321 * argument and radix 10 were given as arguments to the {@link
322 * #toString(int, int)} method.
323 *
324 * @param i an integer to be converted.
325 * @return a string representation of the argument in base 10.
326 */
327 public static String toString(int i) {
328 if (i == Integer.MIN_VALUE)
329 return "-2147483648";
330 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
331 char[] buf = new char[size];
332 getChars(i, size, buf);
333 return new String(0, size, buf);
334 }
335
336 /**
337 * Places characters representing the integer i into the
338 * character array buf. The characters are placed into
339 * the buffer backwards starting with the least significant
340 * digit at the specified index (exclusive), and working
341 * backwards from there.
342 *
343 * Will fail if i == Integer.MIN_VALUE
344 */
345 static void getChars(int i, int index, char[] buf) {
346 int q, r;
347 int charPos = index;
348 char sign = 0;
349
350 if (i < 0) {
351 sign = '-';
352 i = -i;
353 }
354
355 // Generate two digits per iteration
356 while (i >= 65536) {
357 q = i / 100;
358 // really: r = i - (q * 100);
359 r = i - ((q << 6) + (q << 5) + (q << 2));
360 i = q;
361 buf [--charPos] = DigitOnes[r];
362 buf [--charPos] = DigitTens[r];
363 }
364
365 // Fall thru to fast mode for smaller numbers
366 // assert(i <= 65536, i);
367 for (;;) {
368 q = (i * 52429) >>> (16+3);
369 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
370 buf [--charPos] = digits [r];
371 i = q;
372 if (i == 0) break;
373 }
374 if (sign != 0) {
375 buf [--charPos] = sign;
376 }
377 }
378
379 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
380 99999999, 999999999, Integer.MAX_VALUE };
381
382 // Requires positive x
383 static int stringSize(int x) {
384 for (int i=0; ; i++)
385 if (x <= sizeTable[i])
386 return i+1;
387 }
388
389 /**
390 * Parses the string argument as a signed integer in the radix
391 * specified by the second argument. The characters in the string
392 * must all be digits of the specified radix (as determined by
393 * whether {@link java.lang.Character#digit(char, int)} returns a
394 * nonnegative value), except that the first character may be an
395 * ASCII minus sign {@code '-'} (<code>'\u002D'</code>) to
396 * indicate a negative value or an ASCII plus sign {@code '+'}
397 * (<code>'\u002B'</code>) to indicate a positive value. The
398 * resulting integer value is returned.
399 *
400 * <p>An exception of type {@code NumberFormatException} is
401 * thrown if any of the following situations occurs:
402 * <ul>
403 * <li>The first argument is {@code null} or is a string of
404 * length zero.
405 *
406 * <li>The radix is either smaller than
407 * {@link java.lang.Character#MIN_RADIX} or
408 * larger than {@link java.lang.Character#MAX_RADIX}.
409 *
410 * <li>Any character of the string is not a digit of the specified
411 * radix, except that the first character may be a minus sign
412 * {@code '-'} (<code>'\u002D'</code>) or plus sign
413 * {@code '+'} (<code>'\u002B'</code>) provided that the
414 * string is longer than length 1.
415 *
416 * <li>The value represented by the string is not a value of type
417 * {@code int}.
418 * </ul>
419 *
420 * <p>Examples:
421 * <blockquote><pre>
422 * parseInt("0", 10) returns 0
423 * parseInt("473", 10) returns 473
424 * parseInt("+42", 10) returns 42
425 * parseInt("-0", 10) returns 0
426 * parseInt("-FF", 16) returns -255
427 * parseInt("1100110", 2) returns 102
428 * parseInt("2147483647", 10) returns 2147483647
429 * parseInt("-2147483648", 10) returns -2147483648
430 * parseInt("2147483648", 10) throws a NumberFormatException
431 * parseInt("99", 8) throws a NumberFormatException
432 * parseInt("Kona", 10) throws a NumberFormatException
433 * parseInt("Kona", 27) returns 411787
434 * </pre></blockquote>
435 *
436 * @param s the {@code String} containing the integer
437 * representation to be parsed
438 * @param radix the radix to be used while parsing {@code s}.
439 * @return the integer represented by the string argument in the
440 * specified radix.
441 * @exception NumberFormatException if the {@code String}
442 * does not contain a parsable {@code int}.
443 */
444 public static int parseInt(String s, int radix)
445 throws NumberFormatException
446 {
447 /*
448 * WARNING: This method may be invoked early during VM initialization
449 * before IntegerCache is initialized. Care must be taken to not use
450 * the valueOf method.
451 */
452
453 if (s == null) {
454 throw new NumberFormatException("null");
455 }
456
457 if (radix < Character.MIN_RADIX) {
458 throw new NumberFormatException("radix " + radix +
459 " less than Character.MIN_RADIX");
460 }
461
462 if (radix > Character.MAX_RADIX) {
463 throw new NumberFormatException("radix " + radix +
464 " greater than Character.MAX_RADIX");
465 }
466
467 int result = 0;
468 boolean negative = false;
469 int i = 0, len = s.length();
470 int limit = -Integer.MAX_VALUE;
471 int multmin;
472 int digit;
473
474 if (len > 0) {
475 char firstChar = s.charAt(0);
476 if (firstChar < '0') { // Possible leading "+" or "-"
477 if (firstChar == '-') {
478 negative = true;
479 limit = Integer.MIN_VALUE;
480 } else if (firstChar != '+')
481 throw NumberFormatException.forInputString(s);
482
483 if (len == 1) // Cannot have lone "+" or "-"
484 throw NumberFormatException.forInputString(s);
485 i++;
486 }
487 multmin = limit / radix;
488 while (i < len) {
489 // Accumulating negatively avoids surprises near MAX_VALUE
490 digit = Character.digit(s.charAt(i++),radix);
491 if (digit < 0) {
492 throw NumberFormatException.forInputString(s);
493 }
494 if (result < multmin) {
495 throw NumberFormatException.forInputString(s);
496 }
497 result *= radix;
498 if (result < limit + digit) {
499 throw NumberFormatException.forInputString(s);
500 }
501 result -= digit;
502 }
503 } else {
504 throw NumberFormatException.forInputString(s);
505 }
506 return negative ? result : -result;
507 }
508
509 /**
510 * Parses the string argument as a signed decimal integer. The
511 * characters in the string must all be decimal digits, except
512 * that the first character may be an ASCII minus sign {@code '-'}
513 * (<code>'\u002D'</code>) to indicate a negative value or an
514 * ASCII plus sign {@code '+'} (<code>'\u002B'</code>) to
515 * indicate a positive value. The resulting integer value is
516 * returned, exactly as if the argument and the radix 10 were
517 * given as arguments to the {@link #parseInt(java.lang.String,
518 * int)} method.
519 *
520 * @param s a {@code String} containing the {@code int}
521 * representation to be parsed
522 * @return the integer value represented by the argument in decimal.
523 * @exception NumberFormatException if the string does not contain a
524 * parsable integer.
525 */
526 public static int parseInt(String s) throws NumberFormatException {
527 return parseInt(s,10);
528 }
529
530 /**
531 * Returns an {@code Integer} object holding the value
532 * extracted from the specified {@code String} when parsed
533 * with the radix given by the second argument. The first argument
534 * is interpreted as representing a signed integer in the radix
535 * specified by the second argument, exactly as if the arguments
536 * were given to the {@link #parseInt(java.lang.String, int)}
537 * method. The result is an {@code Integer} object that
538 * represents the integer value specified by the string.
539 *
540 * <p>In other words, this method returns an {@code Integer}
541 * object equal to the value of:
542 *
543 * <blockquote>
544 * {@code new Integer(Integer.parseInt(s, radix))}
545 * </blockquote>
546 *
547 * @param s the string to be parsed.
548 * @param radix the radix to be used in interpreting {@code s}
549 * @return an {@code Integer} object holding the value
550 * represented by the string argument in the specified
551 * radix.
552 * @exception NumberFormatException if the {@code String}
553 * does not contain a parsable {@code int}.
554 */
555 public static Integer valueOf(String s, int radix) throws NumberFormatException {
556 return Integer.valueOf(parseInt(s,radix));
557 }
558
559 /**
560 * Returns an {@code Integer} object holding the
561 * value of the specified {@code String}. The argument is
562 * interpreted as representing a signed decimal integer, exactly
563 * as if the argument were given to the {@link
564 * #parseInt(java.lang.String)} method. The result is an
565 * {@code Integer} object that represents the integer value
566 * specified by the string.
567 *
568 * <p>In other words, this method returns an {@code Integer}
569 * object equal to the value of:
570 *
571 * <blockquote>
572 * {@code new Integer(Integer.parseInt(s))}
573 * </blockquote>
574 *
575 * @param s the string to be parsed.
576 * @return an {@code Integer} object holding the value
577 * represented by the string argument.
578 * @exception NumberFormatException if the string cannot be parsed
579 * as an integer.
580 */
581 public static Integer valueOf(String s) throws NumberFormatException {
582 return Integer.valueOf(parseInt(s, 10));
583 }
584
585 /**
586 * Cache to support the object identity semantics of autoboxing for values between
587 * -128 and 127 (inclusive) as required by JLS.
588 *
589 * The cache is initialized on first usage. The size of the cache
590 * may be controlled by the -XX:AutoBoxCacheMax=<size> option.
591 * During VM initialization, java.lang.Integer.IntegerCache.high property
592 * may be set and saved in the private system properties in the
593 * sun.misc.VM class.
594 */
595
596 private static class IntegerCache {
597 static final int low = -128;
598 static final int high;
599 static final Integer cache[];
600
601 static {
602 // high value may be configured by property
603 int h = 127;
604 String integerCacheHighPropValue =
605 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
606 if (integerCacheHighPropValue != null) {
607 int i = parseInt(integerCacheHighPropValue);
608 i = Math.max(i, 127);
609 // Maximum array size is Integer.MAX_VALUE
610 h = Math.min(i, Integer.MAX_VALUE - (-low));
611 }
612 high = h;
613
614 cache = new Integer[(high - low) + 1];
615 int j = low;
616 for(int k = 0; k < cache.length; k++)
617 cache[k] = new Integer(j++);
618 }
619
620 private IntegerCache() {}
621 }
622
623 /**
624 * Returns an {@code Integer} instance representing the specified
625 * {@code int} value. If a new {@code Integer} instance is not
626 * required, this method should generally be used in preference to
627 * the constructor {@link #Integer(int)}, as this method is likely
628 * to yield significantly better space and time performance by
629 * caching frequently requested values.
630 *
631 * This method will always cache values in the range -128 to 127,
632 * inclusive, and may cache other values outside of this range.
633 *
634 * @param i an {@code int} value.
635 * @return an {@code Integer} instance representing {@code i}.
636 * @since 1.5
637 */
638 public static Integer valueOf(int i) {
639 assert IntegerCache.high >= 127;
640 if (i >= IntegerCache.low && i <= IntegerCache.high)
641 return IntegerCache.cache[i + (-IntegerCache.low)];
642 return new Integer(i);
643 }
644
645 /**
646 * The value of the {@code Integer}.
647 *
648 * @serial
649 */
650 private final int value;
651
652 /**
653 * Constructs a newly allocated {@code Integer} object that
654 * represents the specified {@code int} value.
655 *
656 * @param value the value to be represented by the
657 * {@code Integer} object.
658 */
659 public Integer(int value) {
660 this.value = value;
661 }
662
663 /**
664 * Constructs a newly allocated {@code Integer} object that
665 * represents the {@code int} value indicated by the
666 * {@code String} parameter. The string is converted to an
667 * {@code int} value in exactly the manner used by the
668 * {@code parseInt} method for radix 10.
669 *
670 * @param s the {@code String} to be converted to an
671 * {@code Integer}.
672 * @exception NumberFormatException if the {@code String} does not
673 * contain a parsable integer.
674 * @see java.lang.Integer#parseInt(java.lang.String, int)
675 */
676 public Integer(String s) throws NumberFormatException {
677 this.value = parseInt(s, 10);
678 }
679
680 /**
681 * Returns the value of this {@code Integer} as a {@code byte}
682 * after a narrowing primitive conversion.
683 * @jls 5.1.3 Narrowing Primitive Conversions
684 */
685 public byte byteValue() {
686 return (byte)value;
687 }
688
689 /**
690 * Returns the value of this {@code Integer} as a {@code short}
691 * after a narrowing primitive conversion.
692 * @jls 5.1.3 Narrowing Primitive Conversions
693 */
694 public short shortValue() {
695 return (short)value;
696 }
697
698 /**
699 * Returns the value of this {@code Integer} as an
700 * {@code int}.
701 */
702 public int intValue() {
703 return value;
704 }
705
706 /**
707 * Returns the value of this {@code Integer} as a {@code long}
708 * after a widening primitive conversion.
709 * @jls 5.1.2 Widening Primitive Conversions
710 */
711 public long longValue() {
712 return (long)value;
713 }
714
715 /**
716 * Returns the value of this {@code Integer} as a {@code float}
717 * after a widening primitive conversion.
718 * @jls 5.1.2 Widening Primitive Conversions
719 */
720 public float floatValue() {
721 return (float)value;
722 }
723
724 /**
725 * Returns the value of this {@code Integer} as a {@code double}
726 * after a widening primitive conversion.
727 * @jls 5.1.2 Widening Primitive Conversions
728 */
729 public double doubleValue() {
730 return (double)value;
731 }
732
733 /**
734 * Returns a {@code String} object representing this
735 * {@code Integer}'s value. The value is converted to signed
736 * decimal representation and returned as a string, exactly as if
737 * the integer value were given as an argument to the {@link
738 * java.lang.Integer#toString(int)} method.
739 *
740 * @return a string representation of the value of this object in
741 * base 10.
742 */
743 public String toString() {
744 return toString(value);
745 }
746
747 /**
748 * Returns a hash code for this {@code Integer}.
749 *
750 * @return a hash code value for this object, equal to the
751 * primitive {@code int} value represented by this
752 * {@code Integer} object.
753 */
754 public int hashCode() {
755 return value;
756 }
757
758 /**
759 * Returns a hash code for a {@code int} value; compatible with
760 * {@code Integer.hashCode()}.
761 *
762 * @since 1.8
763 *
764 * @return a hash code value for a {@code int} value.
765 */
766 public static int hashCode(int value) {
767 return value;
768 }
769
770 /**
771 * Compares this object to the specified object. The result is
772 * {@code true} if and only if the argument is not
773 * {@code null} and is an {@code Integer} object that
774 * contains the same {@code int} value as this object.
775 *
776 * @param obj the object to compare with.
777 * @return {@code true} if the objects are the same;
778 * {@code false} otherwise.
779 */
780 public boolean equals(Object obj) {
781 if (obj instanceof Integer) {
782 return value == ((Integer)obj).intValue();
783 }
784 return false;
785 }
786
787 /**
788 * Determines the integer value of the system property with the
789 * specified name.
790 *
791 * <p>The first argument is treated as the name of a system
792 * property. System properties are accessible through the {@link
793 * java.lang.System#getProperty(java.lang.String)} method. The
794 * string value of this property is then interpreted as an integer
795 * value using the grammar supported by {@link Integer#decode decode} and
796 * an {@code Integer} object representing this value is returned.
797 *
798 * <p>If there is no property with the specified name, if the
799 * specified name is empty or {@code null}, or if the property
800 * does not have the correct numeric format, then {@code null} is
801 * returned.
802 *
803 * <p>In other words, this method returns an {@code Integer}
804 * object equal to the value of:
805 *
806 * <blockquote>
807 * {@code getInteger(nm, null)}
808 * </blockquote>
809 *
810 * @param nm property name.
811 * @return the {@code Integer} value of the property.
812 * @see java.lang.System#getProperty(java.lang.String)
813 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
814 */
815 public static Integer getInteger(String nm) {
816 return getInteger(nm, null);
817 }
818
819 /**
820 * Determines the integer value of the system property with the
821 * specified name.
822 *
823 * <p>The first argument is treated as the name of a system
824 * property. System properties are accessible through the {@link
825 * java.lang.System#getProperty(java.lang.String)} method. The
826 * string value of this property is then interpreted as an integer
827 * value using the grammar supported by {@link Integer#decode decode} and
828 * an {@code Integer} object representing this value is returned.
829 *
830 * <p>The second argument is the default value. An {@code Integer} object
831 * that represents the value of the second argument is returned if there
832 * is no property of the specified name, if the property does not have
833 * the correct numeric format, or if the specified name is empty or
834 * {@code null}.
835 *
836 * <p>In other words, this method returns an {@code Integer} object
837 * equal to the value of:
838 *
839 * <blockquote>
840 * {@code getInteger(nm, new Integer(val))}
841 * </blockquote>
842 *
843 * but in practice it may be implemented in a manner such as:
844 *
845 * <blockquote><pre>
846 * Integer result = getInteger(nm, null);
847 * return (result == null) ? new Integer(val) : result;
848 * </pre></blockquote>
849 *
850 * to avoid the unnecessary allocation of an {@code Integer}
851 * object when the default value is not needed.
852 *
853 * @param nm property name.
854 * @param val default value.
855 * @return the {@code Integer} value of the property.
856 * @see java.lang.System#getProperty(java.lang.String)
857 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
858 */
859 public static Integer getInteger(String nm, int val) {
860 Integer result = getInteger(nm, null);
861 return (result == null) ? Integer.valueOf(val) : result;
862 }
863
864 /**
865 * Returns the integer value of the system property with the
866 * specified name. The first argument is treated as the name of a
867 * system property. System properties are accessible through the
868 * {@link java.lang.System#getProperty(java.lang.String)} method.
869 * The string value of this property is then interpreted as an
870 * integer value, as per the {@link Integer#decode decode} method,
871 * and an {@code Integer} object representing this value is
872 * returned; in summary:
873 *
874 * <ul><li>If the property value begins with the two ASCII characters
875 * {@code 0x} or the ASCII character {@code #}, not
876 * followed by a minus sign, then the rest of it is parsed as a
877 * hexadecimal integer exactly as by the method
878 * {@link #valueOf(java.lang.String, int)} with radix 16.
879 * <li>If the property value begins with the ASCII character
880 * {@code 0} followed by another character, it is parsed as an
881 * octal integer exactly as by the method
882 * {@link #valueOf(java.lang.String, int)} with radix 8.
883 * <li>Otherwise, the property value is parsed as a decimal integer
884 * exactly as by the method {@link #valueOf(java.lang.String, int)}
885 * with radix 10.
886 * </ul>
887 *
888 * <p>The second argument is the default value. The default value is
889 * returned if there is no property of the specified name, if the
890 * property does not have the correct numeric format, or if the
891 * specified name is empty or {@code null}.
892 *
893 * @param nm property name.
894 * @param val default value.
895 * @return the {@code Integer} value of the property.
896 * @see System#getProperty(java.lang.String)
897 * @see System#getProperty(java.lang.String, java.lang.String)
898 */
899 public static Integer getInteger(String nm, Integer val) {
900 String v = null;
901 try {
902 v = System.getProperty(nm);
903 } catch (IllegalArgumentException | NullPointerException e) {
904 }
905 if (v != null) {
906 try {
907 return Integer.decode(v);
908 } catch (NumberFormatException e) {
909 }
910 }
911 return val;
912 }
913
914 /**
915 * Decodes a {@code String} into an {@code Integer}.
916 * Accepts decimal, hexadecimal, and octal numbers given
917 * by the following grammar:
918 *
919 * <blockquote>
920 * <dl>
921 * <dt><i>DecodableString:</i>
922 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
923 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
924 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
925 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
926 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
927 * <p>
928 * <dt><i>Sign:</i>
929 * <dd>{@code -}
930 * <dd>{@code +}
931 * </dl>
932 * </blockquote>
933 *
934 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
935 * are as defined in section 3.10.1 of
936 * <cite>The Java™ Language Specification</cite>,
937 * except that underscores are not accepted between digits.
938 *
939 * <p>The sequence of characters following an optional
940 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
941 * "{@code #}", or leading zero) is parsed as by the {@code
942 * Integer.parseInt} method with the indicated radix (10, 16, or
943 * 8). This sequence of characters must represent a positive
944 * value or a {@link NumberFormatException} will be thrown. The
945 * result is negated if first character of the specified {@code
946 * String} is the minus sign. No whitespace characters are
947 * permitted in the {@code String}.
948 *
949 * @param nm the {@code String} to decode.
950 * @return an {@code Integer} object holding the {@code int}
951 * value represented by {@code nm}
952 * @exception NumberFormatException if the {@code String} does not
953 * contain a parsable integer.
954 * @see java.lang.Integer#parseInt(java.lang.String, int)
955 */
956 public static Integer decode(String nm) throws NumberFormatException {
957 int radix = 10;
958 int index = 0;
959 boolean negative = false;
960 Integer result;
961
962 if (nm.length() == 0)
963 throw new NumberFormatException("Zero length string");
964 char firstChar = nm.charAt(0);
965 // Handle sign, if present
966 if (firstChar == '-') {
967 negative = true;
968 index++;
969 } else if (firstChar == '+')
970 index++;
971
972 // Handle radix specifier, if present
973 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
974 index += 2;
975 radix = 16;
976 }
977 else if (nm.startsWith("#", index)) {
978 index ++;
979 radix = 16;
980 }
981 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
982 index ++;
983 radix = 8;
984 }
985
986 if (nm.startsWith("-", index) || nm.startsWith("+", index))
987 throw new NumberFormatException("Sign character in wrong position");
988
989 try {
990 result = Integer.valueOf(nm.substring(index), radix);
991 result = negative ? Integer.valueOf(-result.intValue()) : result;
992 } catch (NumberFormatException e) {
993 // If number is Integer.MIN_VALUE, we'll end up here. The next line
994 // handles this case, and causes any genuine format error to be
995 // rethrown.
996 String constant = negative ? ("-" + nm.substring(index))
997 : nm.substring(index);
998 result = Integer.valueOf(constant, radix);
999 }
1000 return result;
1001 }
1002
1003 /**
1004 * Compares two {@code Integer} objects numerically.
1005 *
1006 * @param anotherInteger the {@code Integer} to be compared.
1007 * @return the value {@code 0} if this {@code Integer} is
1008 * equal to the argument {@code Integer}; a value less than
1009 * {@code 0} if this {@code Integer} is numerically less
1010 * than the argument {@code Integer}; and a value greater
1011 * than {@code 0} if this {@code Integer} is numerically
1012 * greater than the argument {@code Integer} (signed
1013 * comparison).
1014 * @since 1.2
1015 */
1016 public int compareTo(Integer anotherInteger) {
1017 return compare(this.value, anotherInteger.value);
1018 }
1019
1020 /**
1021 * Compares two {@code int} values numerically.
1022 * The value returned is identical to what would be returned by:
1023 * <pre>
1024 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1025 * </pre>
1026 *
1027 * @param x the first {@code int} to compare
1028 * @param y the second {@code int} to compare
1029 * @return the value {@code 0} if {@code x == y};
1030 * a value less than {@code 0} if {@code x < y}; and
1031 * a value greater than {@code 0} if {@code x > y}
1032 * @since 1.7
1033 */
1034 public static int compare(int x, int y) {
1035 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1036 }
1037
1038
1039 // Bit twiddling
1040
1041 /**
1042 * The number of bits used to represent an {@code int} value in two's
1043 * complement binary form.
1044 *
1045 * @since 1.5
1046 */
1047 public static final int SIZE = 32;
1048
1049 /**
1050 * The number of bytes used to represent a {@code int} value in two's
1051 * complement binary form.
1052 *
1053 * @since 1.8
1054 */
1055 public static final int BYTES = SIZE / Byte.SIZE;
1056
1057 /**
1058 * Returns an {@code int} value with at most a single one-bit, in the
1059 * position of the highest-order ("leftmost") one-bit in the specified
1060 * {@code int} value. Returns zero if the specified value has no
1061 * one-bits in its two's complement binary representation, that is, if it
1062 * is equal to zero.
1063 *
1064 * @return an {@code int} value with a single one-bit, in the position
1065 * of the highest-order one-bit in the specified value, or zero if
1066 * the specified value is itself equal to zero.
1067 * @since 1.5
1068 */
1069 public static int highestOneBit(int i) {
1070 // HD, Figure 3-1
1071 i |= (i >> 1);
1072 i |= (i >> 2);
1073 i |= (i >> 4);
1074 i |= (i >> 8);
1075 i |= (i >> 16);
1076 return i - (i >>> 1);
1077 }
1078
1079 /**
1080 * Returns an {@code int} value with at most a single one-bit, in the
1081 * position of the lowest-order ("rightmost") one-bit in the specified
1082 * {@code int} value. Returns zero if the specified value has no
1083 * one-bits in its two's complement binary representation, that is, if it
1084 * is equal to zero.
1085 *
1086 * @return an {@code int} value with a single one-bit, in the position
1087 * of the lowest-order one-bit in the specified value, or zero if
1088 * the specified value is itself equal to zero.
1089 * @since 1.5
1090 */
1091 public static int lowestOneBit(int i) {
1092 // HD, Section 2-1
1093 return i & -i;
1094 }
1095
1096 /**
1097 * Returns the number of zero bits preceding the highest-order
1098 * ("leftmost") one-bit in the two's complement binary representation
1099 * of the specified {@code int} value. Returns 32 if the
1100 * specified value has no one-bits in its two's complement representation,
1101 * in other words if it is equal to zero.
1102 *
1103 * <p>Note that this method is closely related to the logarithm base 2.
1104 * For all positive {@code int} values x:
1105 * <ul>
1106 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1107 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1108 * </ul>
1109 *
1110 * @return the number of zero bits preceding the highest-order
1111 * ("leftmost") one-bit in the two's complement binary representation
1112 * of the specified {@code int} value, or 32 if the value
1113 * is equal to zero.
1114 * @since 1.5
1115 */
1116 public static int numberOfLeadingZeros(int i) {
1117 // HD, Figure 5-6
1118 if (i == 0)
1119 return 32;
1120 int n = 1;
1121 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1122 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1123 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1124 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1125 n -= i >>> 31;
1126 return n;
1127 }
1128
1129 /**
1130 * Returns the number of zero bits following the lowest-order ("rightmost")
1131 * one-bit in the two's complement binary representation of the specified
1132 * {@code int} value. Returns 32 if the specified value has no
1133 * one-bits in its two's complement representation, in other words if it is
1134 * equal to zero.
1135 *
1136 * @return the number of zero bits following the lowest-order ("rightmost")
1137 * one-bit in the two's complement binary representation of the
1138 * specified {@code int} value, or 32 if the value is equal
1139 * to zero.
1140 * @since 1.5
1141 */
1142 public static int numberOfTrailingZeros(int i) {
1143 // HD, Figure 5-14
1144 int y;
1145 if (i == 0) return 32;
1146 int n = 31;
1147 y = i <<16; if (y != 0) { n = n -16; i = y; }
1148 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1149 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1150 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1151 return n - ((i << 1) >>> 31);
1152 }
1153
1154 /**
1155 * Returns the number of one-bits in the two's complement binary
1156 * representation of the specified {@code int} value. This function is
1157 * sometimes referred to as the <i>population count</i>.
1158 *
1159 * @return the number of one-bits in the two's complement binary
1160 * representation of the specified {@code int} value.
1161 * @since 1.5
1162 */
1163 public static int bitCount(int i) {
1164 // HD, Figure 5-2
1165 i = i - ((i >>> 1) & 0x55555555);
1166 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1167 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1168 i = i + (i >>> 8);
1169 i = i + (i >>> 16);
1170 return i & 0x3f;
1171 }
1172
1173 /**
1174 * Returns the value obtained by rotating the two's complement binary
1175 * representation of the specified {@code int} value left by the
1176 * specified number of bits. (Bits shifted out of the left hand, or
1177 * high-order, side reenter on the right, or low-order.)
1178 *
1179 * <p>Note that left rotation with a negative distance is equivalent to
1180 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1181 * distance)}. Note also that rotation by any multiple of 32 is a
1182 * no-op, so all but the last five bits of the rotation distance can be
1183 * ignored, even if the distance is negative: {@code rotateLeft(val,
1184 * distance) == rotateLeft(val, distance & 0x1F)}.
1185 *
1186 * @return the value obtained by rotating the two's complement binary
1187 * representation of the specified {@code int} value left by the
1188 * specified number of bits.
1189 * @since 1.5
1190 */
1191 public static int rotateLeft(int i, int distance) {
1192 return (i << distance) | (i >>> -distance);
1193 }
1194
1195 /**
1196 * Returns the value obtained by rotating the two's complement binary
1197 * representation of the specified {@code int} value right by the
1198 * specified number of bits. (Bits shifted out of the right hand, or
1199 * low-order, side reenter on the left, or high-order.)
1200 *
1201 * <p>Note that right rotation with a negative distance is equivalent to
1202 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1203 * distance)}. Note also that rotation by any multiple of 32 is a
1204 * no-op, so all but the last five bits of the rotation distance can be
1205 * ignored, even if the distance is negative: {@code rotateRight(val,
1206 * distance) == rotateRight(val, distance & 0x1F)}.
1207 *
1208 * @return the value obtained by rotating the two's complement binary
1209 * representation of the specified {@code int} value right by the
1210 * specified number of bits.
1211 * @since 1.5
1212 */
1213 public static int rotateRight(int i, int distance) {
1214 return (i >>> distance) | (i << -distance);
1215 }
1216
1217 /**
1218 * Returns the value obtained by reversing the order of the bits in the
1219 * two's complement binary representation of the specified {@code int}
1220 * value.
1221 *
1222 * @return the value obtained by reversing order of the bits in the
1223 * specified {@code int} value.
1224 * @since 1.5
1225 */
1226 public static int reverse(int i) {
1227 // HD, Figure 7-1
1228 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1229 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1230 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1231 i = (i << 24) | ((i & 0xff00) << 8) |
1232 ((i >>> 8) & 0xff00) | (i >>> 24);
1233 return i;
1234 }
1235
1236 /**
1237 * Returns the signum function of the specified {@code int} value. (The
1238 * return value is -1 if the specified value is negative; 0 if the
1239 * specified value is zero; and 1 if the specified value is positive.)
1240 *
1241 * @return the signum function of the specified {@code int} value.
1242 * @since 1.5
1243 */
1244 public static int signum(int i) {
1245 // HD, Section 2-7
1246 return (i >> 31) | (-i >>> 31);
1247 }
1248
1249 /**
1250 * Returns the value obtained by reversing the order of the bytes in the
1251 * two's complement representation of the specified {@code int} value.
1252 *
1253 * @return the value obtained by reversing the bytes in the specified
1254 * {@code int} value.
1255 * @since 1.5
1256 */
1257 public static int reverseBytes(int i) {
1258 return ((i >>> 24) ) |
1259 ((i >> 8) & 0xFF00) |
1260 ((i << 8) & 0xFF0000) |
1261 ((i << 24));
1262 }
1263
1264 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1265 private static final long serialVersionUID = 1360826667806852920L;
1266 }