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 import java.util.Objects;
30
31 /**
32 * The {@code Integer} class wraps a value of the primitive type
33 * {@code int} in an object. An object of type {@code Integer}
34 * contains a single field whose type is {@code int}.
35 *
36 * <p>In addition, this class provides several methods for converting
37 * an {@code int} to a {@code String} and a {@code String} to an
38 * {@code int}, as well as other constants and methods useful when
39 * dealing with an {@code int}.
40 *
41 * <p>Implementation note: The implementations of the "bit twiddling"
42 * methods (such as {@link #highestOneBit(int) highestOneBit} and
43 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
44 * based on material from Henry S. Warren, Jr.'s <i>Hacker's
45 * Delight</i>, (Addison Wesley, 2002).
46 *
47 * @author Lee Boynton
48 * @author Arthur van Hoff
49 * @author Josh Bloch
50 * @author Joseph D. Darcy
51 * @since 1.0
52 */
53 public final class Integer extends Number implements Comparable<Integer> {
54 /**
55 * A constant holding the minimum value an {@code int} can
56 * have, -2<sup>31</sup>.
57 */
58 @Native public static final int MIN_VALUE = 0x80000000;
59
60 /**
61 * A constant holding the maximum value an {@code int} can
62 * have, 2<sup>31</sup>-1.
63 */
64 @Native public static final int MAX_VALUE = 0x7fffffff;
65
66 /**
67 * The {@code Class} instance representing the primitive type
68 * {@code int}.
69 *
70 * @since 1.1
71 */
72 @SuppressWarnings("unchecked")
73 public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
74
75 /**
76 * All possible chars for representing a number as a String
77 */
78 final static char[] digits = {
79 '0' , '1' , '2' , '3' , '4' , '5' ,
80 '6' , '7' , '8' , '9' , 'a' , 'b' ,
81 'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
82 'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
83 'o' , 'p' , 'q' , 'r' , 's' , 't' ,
84 'u' , 'v' , 'w' , 'x' , 'y' , 'z'
85 };
86
87 /**
88 * Returns a string representation of the first argument in the
89 * radix specified by the second argument.
90 *
91 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
92 * or larger than {@code Character.MAX_RADIX}, then the radix
93 * {@code 10} is used instead.
94 *
95 * <p>If the first argument is negative, the first element of the
96 * result is the ASCII minus character {@code '-'}
97 * ({@code '\u005Cu002D'}). If the first argument is not
98 * negative, no sign character appears in the result.
99 *
100 * <p>The remaining characters of the result represent the magnitude
101 * of the first argument. If the magnitude is zero, it is
102 * represented by a single zero character {@code '0'}
103 * ({@code '\u005Cu0030'}); otherwise, the first character of
104 * the representation of the magnitude will not be the zero
105 * character. The following ASCII characters are used as digits:
106 *
107 * <blockquote>
108 * {@code 0123456789abcdefghijklmnopqrstuvwxyz}
109 * </blockquote>
110 *
111 * These are {@code '\u005Cu0030'} through
112 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
113 * {@code '\u005Cu007A'}. If {@code radix} is
114 * <var>N</var>, then the first <var>N</var> of these characters
115 * are used as radix-<var>N</var> digits in the order shown. Thus,
116 * the digits for hexadecimal (radix 16) are
117 * {@code 0123456789abcdef}. If uppercase letters are
118 * desired, the {@link java.lang.String#toUpperCase()} method may
119 * be called on the result:
120 *
121 * <blockquote>
122 * {@code Integer.toString(n, 16).toUpperCase()}
123 * </blockquote>
124 *
125 * @param i an integer to be converted to a string.
126 * @param radix the radix to use in the string representation.
127 * @return a string representation of the argument in the specified radix.
128 * @see java.lang.Character#MAX_RADIX
129 * @see java.lang.Character#MIN_RADIX
130 */
131 public static String toString(int i, int radix) {
132 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
133 radix = 10;
134
135 /* Use the faster version */
136 if (radix == 10) {
137 return toString(i);
138 }
139
140 char buf[] = new char[33];
141 boolean negative = (i < 0);
142 int charPos = 32;
143
144 if (!negative) {
145 i = -i;
146 }
147
148 while (i <= -radix) {
149 buf[charPos--] = digits[-(i % radix)];
150 i = i / radix;
151 }
152 buf[charPos] = digits[-i];
153
154 if (negative) {
155 buf[--charPos] = '-';
156 }
157
158 return new String(buf, charPos, (33 - charPos));
159 }
160
161 /**
162 * Returns a string representation of the first argument as an
163 * unsigned integer value in the radix specified by the second
164 * argument.
165 *
166 * <p>If the radix is smaller than {@code Character.MIN_RADIX}
167 * or larger than {@code Character.MAX_RADIX}, then the radix
168 * {@code 10} is used instead.
169 *
170 * <p>Note that since the first argument is treated as an unsigned
171 * value, no leading sign character is printed.
172 *
173 * <p>If the magnitude is zero, it is represented by a single zero
174 * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
175 * the first character of the representation of the magnitude will
176 * not be the zero character.
177 *
178 * <p>The behavior of radixes and the characters used as digits
179 * are the same as {@link #toString(int, int) toString}.
180 *
181 * @param i an integer to be converted to an unsigned string.
182 * @param radix the radix to use in the string representation.
183 * @return an unsigned string representation of the argument in the specified radix.
184 * @see #toString(int, int)
185 * @since 1.8
186 */
187 public static String toUnsignedString(int i, int radix) {
188 return Long.toUnsignedString(toUnsignedLong(i), radix);
189 }
190
191 /**
192 * Returns a string representation of the integer argument as an
193 * unsigned integer in base 16.
194 *
195 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
196 * if the argument is negative; otherwise, it is equal to the
197 * argument. This value is converted to a string of ASCII digits
198 * in hexadecimal (base 16) with no extra leading
199 * {@code 0}s.
200 *
201 * <p>The value of the argument can be recovered from the returned
202 * string {@code s} by calling {@link
203 * Integer#parseUnsignedInt(String, int)
204 * Integer.parseUnsignedInt(s, 16)}.
205 *
206 * <p>If the unsigned magnitude is zero, it is represented by a
207 * single zero character {@code '0'} ({@code '\u005Cu0030'});
208 * otherwise, the first character of the representation of the
209 * unsigned magnitude will not be the zero character. The
210 * following characters are used as hexadecimal digits:
211 *
212 * <blockquote>
213 * {@code 0123456789abcdef}
214 * </blockquote>
215 *
216 * These are the characters {@code '\u005Cu0030'} through
217 * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
218 * {@code '\u005Cu0066'}. If uppercase letters are
219 * desired, the {@link java.lang.String#toUpperCase()} method may
220 * be called on the result:
221 *
222 * <blockquote>
223 * {@code Integer.toHexString(n).toUpperCase()}
224 * </blockquote>
225 *
226 * @param i an integer to be converted to a string.
227 * @return the string representation of the unsigned integer value
228 * represented by the argument in hexadecimal (base 16).
229 * @see #parseUnsignedInt(String, int)
230 * @see #toUnsignedString(int, int)
231 * @since 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 8.
240 *
241 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
242 * if the argument is negative; otherwise, it is equal to the
243 * argument. This value is converted to a string of ASCII digits
244 * in octal (base 8) with no extra leading {@code 0}s.
245 *
246 * <p>The value of the argument can be recovered from the returned
247 * string {@code s} by calling {@link
248 * Integer#parseUnsignedInt(String, int)
249 * Integer.parseUnsignedInt(s, 8)}.
250 *
251 * <p>If the unsigned magnitude is zero, it is represented by a
252 * single zero character {@code '0'} ({@code '\u005Cu0030'});
253 * otherwise, the first character of the representation of the
254 * unsigned magnitude will not be the zero character. The
255 * following characters are used as octal digits:
256 *
257 * <blockquote>
258 * {@code 01234567}
259 * </blockquote>
260 *
261 * These are the characters {@code '\u005Cu0030'} through
262 * {@code '\u005Cu0037'}.
263 *
264 * @param i an integer to be converted to a string.
265 * @return the string representation of the unsigned integer value
266 * represented by the argument in octal (base 8).
267 * @see #parseUnsignedInt(String, int)
268 * @see #toUnsignedString(int, int)
269 * @since 1.0.2
270 */
271 public static String toOctalString(int i) {
272 return toUnsignedString0(i, 3);
273 }
274
275 /**
276 * Returns a string representation of the integer argument as an
277 * unsigned integer in base 2.
278 *
279 * <p>The unsigned integer value is the argument plus 2<sup>32</sup>
280 * if the argument is negative; otherwise it is equal to the
281 * argument. This value is converted to a string of ASCII digits
282 * in binary (base 2) with no extra leading {@code 0}s.
283 *
284 * <p>The value of the argument can be recovered from the returned
285 * string {@code s} by calling {@link
286 * Integer#parseUnsignedInt(String, int)
287 * Integer.parseUnsignedInt(s, 2)}.
288 *
289 * <p>If the unsigned magnitude is zero, it is represented by a
290 * single zero character {@code '0'} ({@code '\u005Cu0030'});
291 * otherwise, the first character of the representation of the
292 * unsigned magnitude will not be the zero character. The
293 * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
294 * '1'} ({@code '\u005Cu0031'}) are used as binary digits.
295 *
296 * @param i an integer to be converted to a string.
297 * @return the string representation of the unsigned integer value
298 * represented by the argument in binary (base 2).
299 * @see #parseUnsignedInt(String, int)
300 * @see #toUnsignedString(int, int)
301 * @since 1.0.2
302 */
303 public static String toBinaryString(int i) {
304 return toUnsignedString0(i, 1);
305 }
306
307 /**
308 * Convert the integer to an unsigned number.
309 */
310 private static String toUnsignedString0(int val, int shift) {
311 // assert shift > 0 && shift <=5 : "Illegal shift value";
312 int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
313 int chars = Math.max(((mag + (shift - 1)) / shift), 1);
314 char[] buf = new char[chars];
315
316 formatUnsignedInt(val, shift, buf, 0, chars);
317
318 // Use special constructor which takes over "buf".
319 return new String(buf, true);
320 }
321
322 /**
323 * Format an {@code int} (treated as unsigned) into a character buffer. If
324 * {@code len} exceeds the formatted ASCII representation of {@code val},
325 * {@code buf} will be padded with leading zeroes.
326 *
327 * @param val the unsigned int to format
328 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
329 * @param buf the character buffer to write to
330 * @param offset the offset in the destination buffer to start at
331 * @param len the number of characters to write
332 */
333 static void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
334 // assert shift > 0 && shift <=5 : "Illegal shift value";
335 // assert offset >= 0 && offset < buf.length : "illegal offset";
336 // assert len > 0 && (offset + len) <= buf.length : "illegal length";
337 int charPos = offset + len;
338 int radix = 1 << shift;
339 int mask = radix - 1;
340 do {
341 buf[--charPos] = Integer.digits[val & mask];
342 val >>>= shift;
343 } while (charPos > offset);
344 }
345
346 final static char [] DigitTens = {
347 '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
348 '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
349 '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
350 '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
351 '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',
352 '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
353 '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
354 '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
355 '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
356 '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
357 } ;
358
359 final static char [] DigitOnes = {
360 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
361 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
362 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
363 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
364 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
365 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
366 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
367 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
368 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
369 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
370 } ;
371
372 // I use the "invariant division by multiplication" trick to
373 // accelerate Integer.toString. In particular we want to
374 // avoid division by 10.
375 //
376 // The "trick" has roughly the same performance characteristics
377 // as the "classic" Integer.toString code on a non-JIT VM.
378 // The trick avoids .rem and .div calls but has a longer code
379 // path and is thus dominated by dispatch overhead. In the
380 // JIT case the dispatch overhead doesn't exist and the
381 // "trick" is considerably faster than the classic code.
382 //
383 // RE: Division by Invariant Integers using Multiplication
384 // T Gralund, P Montgomery
385 // ACM PLDI 1994
386 //
387
388 /**
389 * Returns a {@code String} object representing the
390 * specified integer. The argument is converted to signed decimal
391 * representation and returned as a string, exactly as if the
392 * argument and radix 10 were given as arguments to the {@link
393 * #toString(int, int)} method.
394 *
395 * @param i an integer to be converted.
396 * @return a string representation of the argument in base 10.
397 */
398 public static String toString(int i) {
399 if (i == Integer.MIN_VALUE)
400 return "-2147483648";
401 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
402 char[] buf = new char[size];
403 getChars(i, size, buf);
404 return new String(buf, true);
405 }
406
407 /**
408 * Returns a string representation of the argument as an unsigned
409 * decimal value.
410 *
411 * The argument is converted to unsigned decimal representation
412 * and returned as a string exactly as if the argument and radix
413 * 10 were given as arguments to the {@link #toUnsignedString(int,
414 * int)} method.
415 *
416 * @param i an integer to be converted to an unsigned string.
417 * @return an unsigned string representation of the argument.
418 * @see #toUnsignedString(int, int)
419 * @since 1.8
420 */
421 public static String toUnsignedString(int i) {
422 return Long.toString(toUnsignedLong(i));
423 }
424
425 /**
426 * Places characters representing the integer i into the
427 * character array buf. The characters are placed into
428 * the buffer backwards starting with the least significant
429 * digit at the specified index (exclusive), and working
430 * backwards from there.
431 *
432 * Will fail if i == Integer.MIN_VALUE
433 */
434 static void getChars(int i, int index, char[] buf) {
435 int q, r;
436 int charPos = index;
437 char sign = 0;
438
439 if (i < 0) {
440 sign = '-';
441 i = -i;
442 }
443
444 // Generate two digits per iteration
445 while (i >= 65536) {
446 q = i / 100;
447 // really: r = i - (q * 100);
448 r = i - ((q << 6) + (q << 5) + (q << 2));
449 i = q;
450 buf [--charPos] = DigitOnes[r];
451 buf [--charPos] = DigitTens[r];
452 }
453
454 // Fall thru to fast mode for smaller numbers
455 // assert(i <= 65536, i);
456 for (;;) {
457 q = (i * 52429) >>> (16+3);
458 r = i - ((q << 3) + (q << 1)); // r = i-(q*10) ...
459 buf [--charPos] = digits [r];
460 i = q;
461 if (i == 0) break;
462 }
463 if (sign != 0) {
464 buf [--charPos] = sign;
465 }
466 }
467
468 final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
469 99999999, 999999999, Integer.MAX_VALUE };
470
471 // Requires positive x
472 static int stringSize(int x) {
473 for (int i=0; ; i++)
474 if (x <= sizeTable[i])
475 return i+1;
476 }
477
478 /**
479 * Parses the string argument as a signed integer in the radix
480 * specified by the second argument. The characters in the string
481 * must all be digits of the specified radix (as determined by
482 * whether {@link java.lang.Character#digit(char, int)} returns a
483 * nonnegative value), except that the first character may be an
484 * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
485 * indicate a negative value or an ASCII plus sign {@code '+'}
486 * ({@code '\u005Cu002B'}) to indicate a positive value. The
487 * resulting integer value is returned.
488 *
489 * <p>An exception of type {@code NumberFormatException} is
490 * thrown if any of the following situations occurs:
491 * <ul>
492 * <li>The first argument is {@code null} or is a string of
493 * length zero.
494 *
495 * <li>The radix is either smaller than
496 * {@link java.lang.Character#MIN_RADIX} or
497 * larger than {@link java.lang.Character#MAX_RADIX}.
498 *
499 * <li>Any character of the string is not a digit of the specified
500 * radix, except that the first character may be a minus sign
501 * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
502 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
503 * string is longer than length 1.
504 *
505 * <li>The value represented by the string is not a value of type
506 * {@code int}.
507 * </ul>
508 *
509 * <p>Examples:
510 * <blockquote><pre>
511 * parseInt("0", 10) returns 0
512 * parseInt("473", 10) returns 473
513 * parseInt("+42", 10) returns 42
514 * parseInt("-0", 10) returns 0
515 * parseInt("-FF", 16) returns -255
516 * parseInt("1100110", 2) returns 102
517 * parseInt("2147483647", 10) returns 2147483647
518 * parseInt("-2147483648", 10) returns -2147483648
519 * parseInt("2147483648", 10) throws a NumberFormatException
520 * parseInt("99", 8) throws a NumberFormatException
521 * parseInt("Kona", 10) throws a NumberFormatException
522 * parseInt("Kona", 27) returns 411787
523 * </pre></blockquote>
524 *
525 * @param s the {@code String} containing the integer
526 * representation to be parsed
527 * @param radix the radix to be used while parsing {@code s}.
528 * @return the integer represented by the string argument in the
529 * specified radix.
530 * @exception NumberFormatException if the {@code String}
531 * does not contain a parsable {@code int}.
532 */
533 public static int parseInt(String s, int radix)
534 throws NumberFormatException
535 {
536 /*
537 * WARNING: This method may be invoked early during VM initialization
538 * before IntegerCache is initialized. Care must be taken to not use
539 * the valueOf method.
540 */
541
542 if (s == null) {
543 throw new NumberFormatException("null");
544 }
545
546 if (radix < Character.MIN_RADIX) {
547 throw new NumberFormatException("radix " + radix +
548 " less than Character.MIN_RADIX");
549 }
550
551 if (radix > Character.MAX_RADIX) {
552 throw new NumberFormatException("radix " + radix +
553 " greater than Character.MAX_RADIX");
554 }
555
556 boolean negative = false;
557 int i = 0, len = s.length();
558 int limit = -Integer.MAX_VALUE;
559
560 if (len > 0) {
561 char firstChar = s.charAt(0);
562 if (firstChar < '0') { // Possible leading "+" or "-"
563 if (firstChar == '-') {
564 negative = true;
565 limit = Integer.MIN_VALUE;
566 } else if (firstChar != '+') {
567 throw NumberFormatException.forInputString(s);
568 }
569
570 if (len == 1) { // Cannot have lone "+" or "-"
571 throw NumberFormatException.forInputString(s);
572 }
573 i++;
574 }
575 int multmin = limit / radix;
576 int result = 0;
577 while (i < len) {
578 // Accumulating negatively avoids surprises near MAX_VALUE
579 int digit = Character.digit(s.charAt(i++), radix);
580 if (digit < 0 || result < multmin) {
581 throw NumberFormatException.forInputString(s);
582 }
583 result *= radix;
584 if (result < limit + digit) {
585 throw NumberFormatException.forInputString(s);
586 }
587 result -= digit;
588 }
589 return negative ? result : -result;
590 } else {
591 throw NumberFormatException.forInputString(s);
592 }
593 }
594
595 /**
596 * Parses the {@link CharSequence} argument as a signed {@code int} in the
597 * specified {@code radix}, beginning at the specified {@code beginIndex}
598 * and extending to the end of the sequence.
599 *
600 * <p>The method does not take steps to guard against the
601 * {@code CharSequence} being mutated while parsing.
602 *
603 * @param s the {@code CharSequence} containing the {@code int}
604 * representation to be parsed
605 * @param radix the radix to be used while parsing {@code s}.
606 * @param beginIndex the beginning index, inclusive.
607 * @return the signed {@code int} represented by the subsequence in
608 * the specified radix.
609 * @throws NullPointerException if {@code s} is null.
610 * @throws IndexOutOfBoundsException if {@code beginIndex} is
611 * negative, or if {@code beginIndex} is greater than
612 * {@code s.length()}.
613 * @throws NumberFormatException if the {@code CharSequence} does not
614 * contain a parsable {@code int} in the specified
615 * {@code radix}, or if {@code radix} is either smaller than
616 * {@link java.lang.Character#MIN_RADIX} or larger than
617 * {@link java.lang.Character#MAX_RADIX}.
618 * @since 1.9
619 */
620 public static int parseInt(CharSequence s, int radix, int beginIndex)
621 throws NumberFormatException {
622 // forces an implicit null check of s
623 return parseInt(s, radix, beginIndex, s.length());
624 }
625
626 /**
627 * Parses the {@link CharSequence} argument as a signed {@code int} in the
628 * specified {@code radix}, beginning at the specified {@code beginIndex}
629 * and extending to {@code endIndex - 1}.
630 *
631 * <p>The method does not take steps to guard against the
632 * {@code CharSequence} being mutated while parsing.
633 *
634 * @param s the {@code CharSequence} containing the {@code int}
635 * representation to be parsed
636 * @param radix the radix to be used while parsing {@code s}.
637 * @param beginIndex the beginning index, inclusive.
638 * @param endIndex the ending index, exclusive.
639 * @return the signed {@code int} represented by the subsequence in
640 * the specified radix.
641 * @throws NullPointerException if {@code s} is null.
642 * @throws IndexOutOfBoundsException if {@code beginIndex} is
643 * negative, or if {@code beginIndex} is greater than
644 * {@code endIndex} or if {@code endIndex} is greater than
645 * {@code s.length()}.
646 * @throws NumberFormatException if the {@code CharSequence} does not
647 * contain a parsable {@code int} in the specified
648 * {@code radix}, or if {@code radix} is either smaller than
649 * {@link java.lang.Character#MIN_RADIX} or larger than
650 * {@link java.lang.Character#MAX_RADIX}.
651 * @since 1.9
652 */
653 public static int parseInt(CharSequence s, int radix, int beginIndex, int endIndex)
654 throws NumberFormatException {
655 s = Objects.requireNonNull(s);
656
657 if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
658 throw new IndexOutOfBoundsException();
659 }
660 if (radix < Character.MIN_RADIX) {
661 throw new NumberFormatException("radix " + radix +
662 " less than Character.MIN_RADIX");
663 }
664 if (radix > Character.MAX_RADIX) {
665 throw new NumberFormatException("radix " + radix +
666 " greater than Character.MAX_RADIX");
667 }
668
669 boolean negative = false;
670 int i = beginIndex;
671 int limit = -Integer.MAX_VALUE;
672
673 if (i < endIndex) {
674 char firstChar = s.charAt(i);
675 if (firstChar < '0') { // Possible leading "+" or "-"
676 if (firstChar == '-') {
677 negative = true;
678 limit = Integer.MIN_VALUE;
679 } else if (firstChar != '+') {
680 throw NumberFormatException.forCharSequence(s, beginIndex,
681 endIndex, i);
682 }
683 i++;
684 if (i == endIndex) { // Cannot have lone "+" or "-"
685 throw NumberFormatException.forCharSequence(s, beginIndex,
686 endIndex, i);
687 }
688 }
689 int multmin = limit / radix;
690 int result = 0;
691 while (i < endIndex) {
692 // Accumulating negatively avoids surprises near MAX_VALUE
693 int digit = Character.digit(s.charAt(i++), radix);
694 if (digit < 0 || result < multmin) {
695 throw NumberFormatException.forCharSequence(s, beginIndex,
696 endIndex, i);
697 }
698 result *= radix;
699 if (result < limit + digit) {
700 throw NumberFormatException.forCharSequence(s, beginIndex,
701 endIndex, i);
702 }
703 result -= digit;
704 }
705 return negative ? result : -result;
706 } else {
707 throw NumberFormatException.forInputString("");
708 }
709 }
710
711 /**
712 * Parses the string argument as a signed decimal integer. The
713 * characters in the string must all be decimal digits, except
714 * that the first character may be an ASCII minus sign {@code '-'}
715 * ({@code '\u005Cu002D'}) to indicate a negative value or an
716 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
717 * indicate a positive value. The resulting integer value is
718 * returned, exactly as if the argument and the radix 10 were
719 * given as arguments to the {@link #parseInt(java.lang.String,
720 * int)} method.
721 *
722 * @param s a {@code String} containing the {@code int}
723 * representation to be parsed
724 * @return the integer value represented by the argument in decimal.
725 * @exception NumberFormatException if the string does not contain a
726 * parsable integer.
727 */
728 public static int parseInt(String s) throws NumberFormatException {
729 return parseInt(s,10);
730 }
731
732 /**
733 * Parses the string argument as an unsigned integer in the radix
734 * specified by the second argument. An unsigned integer maps the
735 * values usually associated with negative numbers to positive
736 * numbers larger than {@code MAX_VALUE}.
737 *
738 * The characters in the string must all be digits of the
739 * specified radix (as determined by whether {@link
740 * java.lang.Character#digit(char, int)} returns a nonnegative
741 * value), except that the first character may be an ASCII plus
742 * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting
743 * integer value is returned.
744 *
745 * <p>An exception of type {@code NumberFormatException} is
746 * thrown if any of the following situations occurs:
747 * <ul>
748 * <li>The first argument is {@code null} or is a string of
749 * length zero.
750 *
751 * <li>The radix is either smaller than
752 * {@link java.lang.Character#MIN_RADIX} or
753 * larger than {@link java.lang.Character#MAX_RADIX}.
754 *
755 * <li>Any character of the string is not a digit of the specified
756 * radix, except that the first character may be a plus sign
757 * {@code '+'} ({@code '\u005Cu002B'}) provided that the
758 * string is longer than length 1.
759 *
760 * <li>The value represented by the string is larger than the
761 * largest unsigned {@code int}, 2<sup>32</sup>-1.
762 *
763 * </ul>
764 *
765 *
766 * @param s the {@code String} containing the unsigned integer
767 * representation to be parsed
768 * @param radix the radix to be used while parsing {@code s}.
769 * @return the integer represented by the string argument in the
770 * specified radix.
771 * @throws NumberFormatException if the {@code String}
772 * does not contain a parsable {@code int}.
773 * @since 1.8
774 */
775 public static int parseUnsignedInt(String s, int radix)
776 throws NumberFormatException {
777 if (s == null) {
778 throw new NumberFormatException("null");
779 }
780
781 int len = s.length();
782 if (len > 0) {
783 char firstChar = s.charAt(0);
784 if (firstChar == '-') {
785 throw new
786 NumberFormatException(String.format("Illegal leading minus sign " +
787 "on unsigned string %s.", s));
788 } else {
789 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
790 (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
791 return parseInt(s, radix);
792 } else {
793 long ell = Long.parseLong(s, radix);
794 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
795 return (int) ell;
796 } else {
797 throw new
798 NumberFormatException(String.format("String value %s exceeds " +
799 "range of unsigned int.", s));
800 }
801 }
802 }
803 } else {
804 throw NumberFormatException.forInputString(s);
805 }
806 }
807
808 /**
809 * Parses the {@link CharSequence} argument as an unsigned {@code int} in
810 * the specified {@code radix}, beginning at the specified
811 * {@code beginIndex} and extending to the end of the sequence.
812 *
813 * <p>The method does not take steps to guard against the
814 * {@code CharSequence} being mutated while parsing.
815 *
816 * @param s the {@code CharSequence} containing the unsigned
817 * {@code int} representation to be parsed
818 * @param radix the radix to be used while parsing {@code s}.
819 * @param beginIndex the beginning index, inclusive.
820 * @return the unsigned {@code int} represented by the subsequence in
821 * the specified radix.
822 * @throws NullPointerException if {@code s} is null.
823 * @throws IndexOutOfBoundsException if {@code beginIndex} is
824 * negative, or if {@code beginIndex} is greater than
825 * {@code s.length()}.
826 * @throws NumberFormatException if the {@code CharSequence} does not
827 * contain a parsable unsigned {@code int} in the specified
828 * {@code radix}, or if {@code radix} is either smaller than
829 * {@link java.lang.Character#MIN_RADIX} or larger than
830 * {@link java.lang.Character#MAX_RADIX}.
831 * @since 1.9
832 */
833 public static int parseUnsignedInt(CharSequence s, int radix, int beginIndex)
834 throws NumberFormatException {
835 // forces an implicit null check of s
836 return parseUnsignedInt(s, radix, beginIndex, s.length());
837 }
838
839 /**
840 * Parses the {@link CharSequence} argument as an unsigned {@code int} in
841 * the specified {@code radix}, beginning at the specified
842 * {@code beginIndex} and extending to {@code endIndex - 1}.
843 *
844 * <p>The method does not take steps to guard against the
845 * {@code CharSequence} being mutated while parsing.
846 *
847 * @param s the {@code CharSequence} containing the unsigned
848 * {@code int} representation to be parsed
849 * @param radix the radix to be used while parsing {@code s}.
850 * @param beginIndex the beginning index, inclusive.
851 * @param endIndex the ending index, exclusive.
852 * @return the unsigned {@code int} represented by the subsequence in
853 * the specified radix.
854 * @throws NullPointerException if {@code s} is null.
855 * @throws IndexOutOfBoundsException if {@code beginIndex} is
856 * negative, or if {@code beginIndex} is greater than
857 * {@code endIndex} or if {@code endIndex} is greater than
858 * {@code s.length()}.
859 * @throws NumberFormatException if the {@code CharSequence} does not
860 * contain a parsable unsigned {@code int} in the specified
861 * {@code radix}, or if {@code radix} is either smaller than
862 * {@link java.lang.Character#MIN_RADIX} or larger than
863 * {@link java.lang.Character#MAX_RADIX}.
864 * @since 1.9
865 */
866 public static int parseUnsignedInt(CharSequence s, int radix, int beginIndex, int endIndex)
867 throws NumberFormatException {
868 s = Objects.requireNonNull(s);
869
870 if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
871 throw new IndexOutOfBoundsException();
872 }
873 int start = beginIndex, len = endIndex - beginIndex;
874
875 if (len > 0) {
876 char firstChar = s.charAt(start);
877 if (firstChar == '-') {
878 throw new
879 NumberFormatException(String.format("Illegal leading minus sign " +
880 "on unsigned string %s.", s));
881 } else {
882 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
883 (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits
884 return parseInt(s, radix, start, start + len);
885 } else {
886 long ell = Long.parseLong(s, radix, start, start + len);
887 if ((ell & 0xffff_ffff_0000_0000L) == 0) {
888 return (int) ell;
889 } else {
890 throw new
891 NumberFormatException(String.format("String value %s exceeds " +
892 "range of unsigned int.", s));
893 }
894 }
895 }
896 } else {
897 throw new NumberFormatException("");
898 }
899 }
900
901 /**
902 * Parses the string argument as an unsigned decimal integer. The
903 * characters in the string must all be decimal digits, except
904 * that the first character may be an an ASCII plus sign {@code
905 * '+'} ({@code '\u005Cu002B'}). The resulting integer value
906 * is returned, exactly as if the argument and the radix 10 were
907 * given as arguments to the {@link
908 * #parseUnsignedInt(java.lang.String, int)} method.
909 *
910 * @param s a {@code String} containing the unsigned {@code int}
911 * representation to be parsed
912 * @return the unsigned integer value represented by the argument in decimal.
913 * @throws NumberFormatException if the string does not contain a
914 * parsable unsigned integer.
915 * @since 1.8
916 */
917 public static int parseUnsignedInt(String s) throws NumberFormatException {
918 return parseUnsignedInt(s, 10);
919 }
920
921 /**
922 * Returns an {@code Integer} object holding the value
923 * extracted from the specified {@code String} when parsed
924 * with the radix given by the second argument. The first argument
925 * is interpreted as representing a signed integer in the radix
926 * specified by the second argument, exactly as if the arguments
927 * were given to the {@link #parseInt(java.lang.String, int)}
928 * method. The result is an {@code Integer} object that
929 * represents the integer value specified by the string.
930 *
931 * <p>In other words, this method returns an {@code Integer}
932 * object equal to the value of:
933 *
934 * <blockquote>
935 * {@code new Integer(Integer.parseInt(s, radix))}
936 * </blockquote>
937 *
938 * @param s the string to be parsed.
939 * @param radix the radix to be used in interpreting {@code s}
940 * @return an {@code Integer} object holding the value
941 * represented by the string argument in the specified
942 * radix.
943 * @exception NumberFormatException if the {@code String}
944 * does not contain a parsable {@code int}.
945 */
946 public static Integer valueOf(String s, int radix) throws NumberFormatException {
947 return Integer.valueOf(parseInt(s,radix));
948 }
949
950 /**
951 * Returns an {@code Integer} object holding the
952 * value of the specified {@code String}. The argument is
953 * interpreted as representing a signed decimal integer, exactly
954 * as if the argument were given to the {@link
955 * #parseInt(java.lang.String)} method. The result is an
956 * {@code Integer} object that represents the integer value
957 * specified by the string.
958 *
959 * <p>In other words, this method returns an {@code Integer}
960 * object equal to the value of:
961 *
962 * <blockquote>
963 * {@code new Integer(Integer.parseInt(s))}
964 * </blockquote>
965 *
966 * @param s the string to be parsed.
967 * @return an {@code Integer} object holding the value
968 * represented by the string argument.
969 * @exception NumberFormatException if the string cannot be parsed
970 * as an integer.
971 */
972 public static Integer valueOf(String s) throws NumberFormatException {
973 return Integer.valueOf(parseInt(s, 10));
974 }
975
976 /**
977 * Cache to support the object identity semantics of autoboxing for values between
978 * -128 and 127 (inclusive) as required by JLS.
979 *
980 * The cache is initialized on first usage. The size of the cache
981 * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
982 * During VM initialization, java.lang.Integer.IntegerCache.high property
983 * may be set and saved in the private system properties in the
984 * sun.misc.VM class.
985 */
986
987 private static class IntegerCache {
988 static final int low = -128;
989 static final int high;
990 static final Integer cache[];
991
992 static {
993 // high value may be configured by property
994 int h = 127;
995 String integerCacheHighPropValue =
996 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
997 if (integerCacheHighPropValue != null) {
998 try {
999 int i = parseInt(integerCacheHighPropValue);
1000 i = Math.max(i, 127);
1001 // Maximum array size is Integer.MAX_VALUE
1002 h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
1003 } catch( NumberFormatException nfe) {
1004 // If the property cannot be parsed into an int, ignore it.
1005 }
1006 }
1007 high = h;
1008
1009 cache = new Integer[(high - low) + 1];
1010 int j = low;
1011 for(int k = 0; k < cache.length; k++)
1012 cache[k] = new Integer(j++);
1013
1014 // range [-128, 127] must be interned (JLS7 5.1.7)
1015 assert IntegerCache.high >= 127;
1016 }
1017
1018 private IntegerCache() {}
1019 }
1020
1021 /**
1022 * Returns an {@code Integer} instance representing the specified
1023 * {@code int} value. If a new {@code Integer} instance is not
1024 * required, this method should generally be used in preference to
1025 * the constructor {@link #Integer(int)}, as this method is likely
1026 * to yield significantly better space and time performance by
1027 * caching frequently requested values.
1028 *
1029 * This method will always cache values in the range -128 to 127,
1030 * inclusive, and may cache other values outside of this range.
1031 *
1032 * @param i an {@code int} value.
1033 * @return an {@code Integer} instance representing {@code i}.
1034 * @since 1.5
1035 */
1036 public static Integer valueOf(int i) {
1037 if (i >= IntegerCache.low && i <= IntegerCache.high)
1038 return IntegerCache.cache[i + (-IntegerCache.low)];
1039 return new Integer(i);
1040 }
1041
1042 /**
1043 * The value of the {@code Integer}.
1044 *
1045 * @serial
1046 */
1047 private final int value;
1048
1049 /**
1050 * Constructs a newly allocated {@code Integer} object that
1051 * represents the specified {@code int} value.
1052 *
1053 * @param value the value to be represented by the
1054 * {@code Integer} object.
1055 */
1056 public Integer(int value) {
1057 this.value = value;
1058 }
1059
1060 /**
1061 * Constructs a newly allocated {@code Integer} object that
1062 * represents the {@code int} value indicated by the
1063 * {@code String} parameter. The string is converted to an
1064 * {@code int} value in exactly the manner used by the
1065 * {@code parseInt} method for radix 10.
1066 *
1067 * @param s the {@code String} to be converted to an
1068 * {@code Integer}.
1069 * @exception NumberFormatException if the {@code String} does not
1070 * contain a parsable integer.
1071 * @see java.lang.Integer#parseInt(java.lang.String, int)
1072 */
1073 public Integer(String s) throws NumberFormatException {
1074 this.value = parseInt(s, 10);
1075 }
1076
1077 /**
1078 * Returns the value of this {@code Integer} as a {@code byte}
1079 * after a narrowing primitive conversion.
1080 * @jls 5.1.3 Narrowing Primitive Conversions
1081 */
1082 public byte byteValue() {
1083 return (byte)value;
1084 }
1085
1086 /**
1087 * Returns the value of this {@code Integer} as a {@code short}
1088 * after a narrowing primitive conversion.
1089 * @jls 5.1.3 Narrowing Primitive Conversions
1090 */
1091 public short shortValue() {
1092 return (short)value;
1093 }
1094
1095 /**
1096 * Returns the value of this {@code Integer} as an
1097 * {@code int}.
1098 */
1099 public int intValue() {
1100 return value;
1101 }
1102
1103 /**
1104 * Returns the value of this {@code Integer} as a {@code long}
1105 * after a widening primitive conversion.
1106 * @jls 5.1.2 Widening Primitive Conversions
1107 * @see Integer#toUnsignedLong(int)
1108 */
1109 public long longValue() {
1110 return (long)value;
1111 }
1112
1113 /**
1114 * Returns the value of this {@code Integer} as a {@code float}
1115 * after a widening primitive conversion.
1116 * @jls 5.1.2 Widening Primitive Conversions
1117 */
1118 public float floatValue() {
1119 return (float)value;
1120 }
1121
1122 /**
1123 * Returns the value of this {@code Integer} as a {@code double}
1124 * after a widening primitive conversion.
1125 * @jls 5.1.2 Widening Primitive Conversions
1126 */
1127 public double doubleValue() {
1128 return (double)value;
1129 }
1130
1131 /**
1132 * Returns a {@code String} object representing this
1133 * {@code Integer}'s value. The value is converted to signed
1134 * decimal representation and returned as a string, exactly as if
1135 * the integer value were given as an argument to the {@link
1136 * java.lang.Integer#toString(int)} method.
1137 *
1138 * @return a string representation of the value of this object in
1139 * base 10.
1140 */
1141 public String toString() {
1142 return toString(value);
1143 }
1144
1145 /**
1146 * Returns a hash code for this {@code Integer}.
1147 *
1148 * @return a hash code value for this object, equal to the
1149 * primitive {@code int} value represented by this
1150 * {@code Integer} object.
1151 */
1152 @Override
1153 public int hashCode() {
1154 return Integer.hashCode(value);
1155 }
1156
1157 /**
1158 * Returns a hash code for a {@code int} value; compatible with
1159 * {@code Integer.hashCode()}.
1160 *
1161 * @param value the value to hash
1162 * @since 1.8
1163 *
1164 * @return a hash code value for a {@code int} value.
1165 */
1166 public static int hashCode(int value) {
1167 return value;
1168 }
1169
1170 /**
1171 * Compares this object to the specified object. The result is
1172 * {@code true} if and only if the argument is not
1173 * {@code null} and is an {@code Integer} object that
1174 * contains the same {@code int} value as this object.
1175 *
1176 * @param obj the object to compare with.
1177 * @return {@code true} if the objects are the same;
1178 * {@code false} otherwise.
1179 */
1180 public boolean equals(Object obj) {
1181 if (obj instanceof Integer) {
1182 return value == ((Integer)obj).intValue();
1183 }
1184 return false;
1185 }
1186
1187 /**
1188 * Determines the integer value of the system property with the
1189 * specified name.
1190 *
1191 * <p>The first argument is treated as the name of a system
1192 * property. System properties are accessible through the {@link
1193 * java.lang.System#getProperty(java.lang.String)} method. The
1194 * string value of this property is then interpreted as an integer
1195 * value using the grammar supported by {@link Integer#decode decode} and
1196 * an {@code Integer} object representing this value is returned.
1197 *
1198 * <p>If there is no property with the specified name, if the
1199 * specified name is empty or {@code null}, or if the property
1200 * does not have the correct numeric format, then {@code null} is
1201 * returned.
1202 *
1203 * <p>In other words, this method returns an {@code Integer}
1204 * object equal to the value of:
1205 *
1206 * <blockquote>
1207 * {@code getInteger(nm, null)}
1208 * </blockquote>
1209 *
1210 * @param nm property name.
1211 * @return the {@code Integer} value of the property.
1212 * @throws SecurityException for the same reasons as
1213 * {@link System#getProperty(String) System.getProperty}
1214 * @see java.lang.System#getProperty(java.lang.String)
1215 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1216 */
1217 public static Integer getInteger(String nm) {
1218 return getInteger(nm, null);
1219 }
1220
1221 /**
1222 * Determines the integer value of the system property with the
1223 * specified name.
1224 *
1225 * <p>The first argument is treated as the name of a system
1226 * property. System properties are accessible through the {@link
1227 * java.lang.System#getProperty(java.lang.String)} method. The
1228 * string value of this property is then interpreted as an integer
1229 * value using the grammar supported by {@link Integer#decode decode} and
1230 * an {@code Integer} object representing this value is returned.
1231 *
1232 * <p>The second argument is the default value. An {@code Integer} object
1233 * that represents the value of the second argument is returned if there
1234 * is no property of the specified name, if the property does not have
1235 * the correct numeric format, or if the specified name is empty or
1236 * {@code null}.
1237 *
1238 * <p>In other words, this method returns an {@code Integer} object
1239 * equal to the value of:
1240 *
1241 * <blockquote>
1242 * {@code getInteger(nm, new Integer(val))}
1243 * </blockquote>
1244 *
1245 * but in practice it may be implemented in a manner such as:
1246 *
1247 * <blockquote><pre>
1248 * Integer result = getInteger(nm, null);
1249 * return (result == null) ? new Integer(val) : result;
1250 * </pre></blockquote>
1251 *
1252 * to avoid the unnecessary allocation of an {@code Integer}
1253 * object when the default value is not needed.
1254 *
1255 * @param nm property name.
1256 * @param val default value.
1257 * @return the {@code Integer} value of the property.
1258 * @throws SecurityException for the same reasons as
1259 * {@link System#getProperty(String) System.getProperty}
1260 * @see java.lang.System#getProperty(java.lang.String)
1261 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
1262 */
1263 public static Integer getInteger(String nm, int val) {
1264 Integer result = getInteger(nm, null);
1265 return (result == null) ? Integer.valueOf(val) : result;
1266 }
1267
1268 /**
1269 * Returns the integer value of the system property with the
1270 * specified name. The first argument is treated as the name of a
1271 * system property. System properties are accessible through the
1272 * {@link java.lang.System#getProperty(java.lang.String)} method.
1273 * The string value of this property is then interpreted as an
1274 * integer value, as per the {@link Integer#decode decode} method,
1275 * and an {@code Integer} object representing this value is
1276 * returned; in summary:
1277 *
1278 * <ul><li>If the property value begins with the two ASCII characters
1279 * {@code 0x} or the ASCII character {@code #}, not
1280 * followed by a minus sign, then the rest of it is parsed as a
1281 * hexadecimal integer exactly as by the method
1282 * {@link #valueOf(java.lang.String, int)} with radix 16.
1283 * <li>If the property value begins with the ASCII character
1284 * {@code 0} followed by another character, it is parsed as an
1285 * octal integer exactly as by the method
1286 * {@link #valueOf(java.lang.String, int)} with radix 8.
1287 * <li>Otherwise, the property value is parsed as a decimal integer
1288 * exactly as by the method {@link #valueOf(java.lang.String, int)}
1289 * with radix 10.
1290 * </ul>
1291 *
1292 * <p>The second argument is the default value. The default value is
1293 * returned if there is no property of the specified name, if the
1294 * property does not have the correct numeric format, or if the
1295 * specified name is empty or {@code null}.
1296 *
1297 * @param nm property name.
1298 * @param val default value.
1299 * @return the {@code Integer} value of the property.
1300 * @throws SecurityException for the same reasons as
1301 * {@link System#getProperty(String) System.getProperty}
1302 * @see System#getProperty(java.lang.String)
1303 * @see System#getProperty(java.lang.String, java.lang.String)
1304 */
1305 public static Integer getInteger(String nm, Integer val) {
1306 String v = null;
1307 try {
1308 v = System.getProperty(nm);
1309 } catch (IllegalArgumentException | NullPointerException e) {
1310 }
1311 if (v != null) {
1312 try {
1313 return Integer.decode(v);
1314 } catch (NumberFormatException e) {
1315 }
1316 }
1317 return val;
1318 }
1319
1320 /**
1321 * Decodes a {@code String} into an {@code Integer}.
1322 * Accepts decimal, hexadecimal, and octal numbers given
1323 * by the following grammar:
1324 *
1325 * <blockquote>
1326 * <dl>
1327 * <dt><i>DecodableString:</i>
1328 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
1329 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
1330 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
1331 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
1332 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
1333 *
1334 * <dt><i>Sign:</i>
1335 * <dd>{@code -}
1336 * <dd>{@code +}
1337 * </dl>
1338 * </blockquote>
1339 *
1340 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
1341 * are as defined in section 3.10.1 of
1342 * <cite>The Java™ Language Specification</cite>,
1343 * except that underscores are not accepted between digits.
1344 *
1345 * <p>The sequence of characters following an optional
1346 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
1347 * "{@code #}", or leading zero) is parsed as by the {@code
1348 * Integer.parseInt} method with the indicated radix (10, 16, or
1349 * 8). This sequence of characters must represent a positive
1350 * value or a {@link NumberFormatException} will be thrown. The
1351 * result is negated if first character of the specified {@code
1352 * String} is the minus sign. No whitespace characters are
1353 * permitted in the {@code String}.
1354 *
1355 * @param nm the {@code String} to decode.
1356 * @return an {@code Integer} object holding the {@code int}
1357 * value represented by {@code nm}
1358 * @exception NumberFormatException if the {@code String} does not
1359 * contain a parsable integer.
1360 * @see java.lang.Integer#parseInt(java.lang.String, int)
1361 */
1362 public static Integer decode(String nm) throws NumberFormatException {
1363 int radix = 10;
1364 int index = 0;
1365 boolean negative = false;
1366 Integer result;
1367
1368 if (nm.length() == 0)
1369 throw new NumberFormatException("Zero length string");
1370 char firstChar = nm.charAt(0);
1371 // Handle sign, if present
1372 if (firstChar == '-') {
1373 negative = true;
1374 index++;
1375 } else if (firstChar == '+')
1376 index++;
1377
1378 // Handle radix specifier, if present
1379 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {
1380 index += 2;
1381 radix = 16;
1382 }
1383 else if (nm.startsWith("#", index)) {
1384 index ++;
1385 radix = 16;
1386 }
1387 else if (nm.startsWith("0", index) && nm.length() > 1 + index) {
1388 index ++;
1389 radix = 8;
1390 }
1391
1392 if (nm.startsWith("-", index) || nm.startsWith("+", index))
1393 throw new NumberFormatException("Sign character in wrong position");
1394
1395 try {
1396 result = Integer.valueOf(nm.substring(index), radix);
1397 result = negative ? Integer.valueOf(-result.intValue()) : result;
1398 } catch (NumberFormatException e) {
1399 // If number is Integer.MIN_VALUE, we'll end up here. The next line
1400 // handles this case, and causes any genuine format error to be
1401 // rethrown.
1402 String constant = negative ? ("-" + nm.substring(index))
1403 : nm.substring(index);
1404 result = Integer.valueOf(constant, radix);
1405 }
1406 return result;
1407 }
1408
1409 /**
1410 * Compares two {@code Integer} objects numerically.
1411 *
1412 * @param anotherInteger the {@code Integer} to be compared.
1413 * @return the value {@code 0} if this {@code Integer} is
1414 * equal to the argument {@code Integer}; a value less than
1415 * {@code 0} if this {@code Integer} is numerically less
1416 * than the argument {@code Integer}; and a value greater
1417 * than {@code 0} if this {@code Integer} is numerically
1418 * greater than the argument {@code Integer} (signed
1419 * comparison).
1420 * @since 1.2
1421 */
1422 public int compareTo(Integer anotherInteger) {
1423 return compare(this.value, anotherInteger.value);
1424 }
1425
1426 /**
1427 * Compares two {@code int} values numerically.
1428 * The value returned is identical to what would be returned by:
1429 * <pre>
1430 * Integer.valueOf(x).compareTo(Integer.valueOf(y))
1431 * </pre>
1432 *
1433 * @param x the first {@code int} to compare
1434 * @param y the second {@code int} to compare
1435 * @return the value {@code 0} if {@code x == y};
1436 * a value less than {@code 0} if {@code x < y}; and
1437 * a value greater than {@code 0} if {@code x > y}
1438 * @since 1.7
1439 */
1440 public static int compare(int x, int y) {
1441 return (x < y) ? -1 : ((x == y) ? 0 : 1);
1442 }
1443
1444 /**
1445 * Compares two {@code int} values numerically treating the values
1446 * as unsigned.
1447 *
1448 * @param x the first {@code int} to compare
1449 * @param y the second {@code int} to compare
1450 * @return the value {@code 0} if {@code x == y}; a value less
1451 * than {@code 0} if {@code x < y} as unsigned values; and
1452 * a value greater than {@code 0} if {@code x > y} as
1453 * unsigned values
1454 * @since 1.8
1455 */
1456 public static int compareUnsigned(int x, int y) {
1457 return compare(x + MIN_VALUE, y + MIN_VALUE);
1458 }
1459
1460 /**
1461 * Converts the argument to a {@code long} by an unsigned
1462 * conversion. In an unsigned conversion to a {@code long}, the
1463 * high-order 32 bits of the {@code long} are zero and the
1464 * low-order 32 bits are equal to the bits of the integer
1465 * argument.
1466 *
1467 * Consequently, zero and positive {@code int} values are mapped
1468 * to a numerically equal {@code long} value and negative {@code
1469 * int} values are mapped to a {@code long} value equal to the
1470 * input plus 2<sup>32</sup>.
1471 *
1472 * @param x the value to convert to an unsigned {@code long}
1473 * @return the argument converted to {@code long} by an unsigned
1474 * conversion
1475 * @since 1.8
1476 */
1477 public static long toUnsignedLong(int x) {
1478 return ((long) x) & 0xffffffffL;
1479 }
1480
1481 /**
1482 * Returns the unsigned quotient of dividing the first argument by
1483 * the second where each argument and the result is interpreted as
1484 * an unsigned value.
1485 *
1486 * <p>Note that in two's complement arithmetic, the three other
1487 * basic arithmetic operations of add, subtract, and multiply are
1488 * bit-wise identical if the two operands are regarded as both
1489 * being signed or both being unsigned. Therefore separate {@code
1490 * addUnsigned}, etc. methods are not provided.
1491 *
1492 * @param dividend the value to be divided
1493 * @param divisor the value doing the dividing
1494 * @return the unsigned quotient of the first argument divided by
1495 * the second argument
1496 * @see #remainderUnsigned
1497 * @since 1.8
1498 */
1499 public static int divideUnsigned(int dividend, int divisor) {
1500 // In lieu of tricky code, for now just use long arithmetic.
1501 return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
1502 }
1503
1504 /**
1505 * Returns the unsigned remainder from dividing the first argument
1506 * by the second where each argument and the result is interpreted
1507 * as an unsigned value.
1508 *
1509 * @param dividend the value to be divided
1510 * @param divisor the value doing the dividing
1511 * @return the unsigned remainder of the first argument divided by
1512 * the second argument
1513 * @see #divideUnsigned
1514 * @since 1.8
1515 */
1516 public static int remainderUnsigned(int dividend, int divisor) {
1517 // In lieu of tricky code, for now just use long arithmetic.
1518 return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
1519 }
1520
1521
1522 // Bit twiddling
1523
1524 /**
1525 * The number of bits used to represent an {@code int} value in two's
1526 * complement binary form.
1527 *
1528 * @since 1.5
1529 */
1530 @Native public static final int SIZE = 32;
1531
1532 /**
1533 * The number of bytes used to represent a {@code int} value in two's
1534 * complement binary form.
1535 *
1536 * @since 1.8
1537 */
1538 public static final int BYTES = SIZE / Byte.SIZE;
1539
1540 /**
1541 * Returns an {@code int} value with at most a single one-bit, in the
1542 * position of the highest-order ("leftmost") one-bit in the specified
1543 * {@code int} value. Returns zero if the specified value has no
1544 * one-bits in its two's complement binary representation, that is, if it
1545 * is equal to zero.
1546 *
1547 * @param i the value whose highest one bit is to be computed
1548 * @return an {@code int} value with a single one-bit, in the position
1549 * of the highest-order one-bit in the specified value, or zero if
1550 * the specified value is itself equal to zero.
1551 * @since 1.5
1552 */
1553 public static int highestOneBit(int i) {
1554 // HD, Figure 3-1
1555 i |= (i >> 1);
1556 i |= (i >> 2);
1557 i |= (i >> 4);
1558 i |= (i >> 8);
1559 i |= (i >> 16);
1560 return i - (i >>> 1);
1561 }
1562
1563 /**
1564 * Returns an {@code int} value with at most a single one-bit, in the
1565 * position of the lowest-order ("rightmost") one-bit in the specified
1566 * {@code int} value. Returns zero if the specified value has no
1567 * one-bits in its two's complement binary representation, that is, if it
1568 * is equal to zero.
1569 *
1570 * @param i the value whose lowest one bit is to be computed
1571 * @return an {@code int} value with a single one-bit, in the position
1572 * of the lowest-order one-bit in the specified value, or zero if
1573 * the specified value is itself equal to zero.
1574 * @since 1.5
1575 */
1576 public static int lowestOneBit(int i) {
1577 // HD, Section 2-1
1578 return i & -i;
1579 }
1580
1581 /**
1582 * Returns the number of zero bits preceding the highest-order
1583 * ("leftmost") one-bit in the two's complement binary representation
1584 * of the specified {@code int} value. Returns 32 if the
1585 * specified value has no one-bits in its two's complement representation,
1586 * in other words if it is equal to zero.
1587 *
1588 * <p>Note that this method is closely related to the logarithm base 2.
1589 * For all positive {@code int} values x:
1590 * <ul>
1591 * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
1592 * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
1593 * </ul>
1594 *
1595 * @param i the value whose number of leading zeros is to be computed
1596 * @return the number of zero bits preceding the highest-order
1597 * ("leftmost") one-bit in the two's complement binary representation
1598 * of the specified {@code int} value, or 32 if the value
1599 * is equal to zero.
1600 * @since 1.5
1601 */
1602 public static int numberOfLeadingZeros(int i) {
1603 // HD, Figure 5-6
1604 if (i == 0)
1605 return 32;
1606 int n = 1;
1607 if (i >>> 16 == 0) { n += 16; i <<= 16; }
1608 if (i >>> 24 == 0) { n += 8; i <<= 8; }
1609 if (i >>> 28 == 0) { n += 4; i <<= 4; }
1610 if (i >>> 30 == 0) { n += 2; i <<= 2; }
1611 n -= i >>> 31;
1612 return n;
1613 }
1614
1615 /**
1616 * Returns the number of zero bits following the lowest-order ("rightmost")
1617 * one-bit in the two's complement binary representation of the specified
1618 * {@code int} value. Returns 32 if the specified value has no
1619 * one-bits in its two's complement representation, in other words if it is
1620 * equal to zero.
1621 *
1622 * @param i the value whose number of trailing zeros is to be computed
1623 * @return the number of zero bits following the lowest-order ("rightmost")
1624 * one-bit in the two's complement binary representation of the
1625 * specified {@code int} value, or 32 if the value is equal
1626 * to zero.
1627 * @since 1.5
1628 */
1629 public static int numberOfTrailingZeros(int i) {
1630 // HD, Figure 5-14
1631 int y;
1632 if (i == 0) return 32;
1633 int n = 31;
1634 y = i <<16; if (y != 0) { n = n -16; i = y; }
1635 y = i << 8; if (y != 0) { n = n - 8; i = y; }
1636 y = i << 4; if (y != 0) { n = n - 4; i = y; }
1637 y = i << 2; if (y != 0) { n = n - 2; i = y; }
1638 return n - ((i << 1) >>> 31);
1639 }
1640
1641 /**
1642 * Returns the number of one-bits in the two's complement binary
1643 * representation of the specified {@code int} value. This function is
1644 * sometimes referred to as the <i>population count</i>.
1645 *
1646 * @param i the value whose bits are to be counted
1647 * @return the number of one-bits in the two's complement binary
1648 * representation of the specified {@code int} value.
1649 * @since 1.5
1650 */
1651 public static int bitCount(int i) {
1652 // HD, Figure 5-2
1653 i = i - ((i >>> 1) & 0x55555555);
1654 i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
1655 i = (i + (i >>> 4)) & 0x0f0f0f0f;
1656 i = i + (i >>> 8);
1657 i = i + (i >>> 16);
1658 return i & 0x3f;
1659 }
1660
1661 /**
1662 * Returns the value obtained by rotating the two's complement binary
1663 * representation of the specified {@code int} value left by the
1664 * specified number of bits. (Bits shifted out of the left hand, or
1665 * high-order, side reenter on the right, or low-order.)
1666 *
1667 * <p>Note that left rotation with a negative distance is equivalent to
1668 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
1669 * distance)}. Note also that rotation by any multiple of 32 is a
1670 * no-op, so all but the last five bits of the rotation distance can be
1671 * ignored, even if the distance is negative: {@code rotateLeft(val,
1672 * distance) == rotateLeft(val, distance & 0x1F)}.
1673 *
1674 * @param i the value whose bits are to be rotated left
1675 * @param distance the number of bit positions to rotate left
1676 * @return the value obtained by rotating the two's complement binary
1677 * representation of the specified {@code int} value left by the
1678 * specified number of bits.
1679 * @since 1.5
1680 */
1681 public static int rotateLeft(int i, int distance) {
1682 return (i << distance) | (i >>> -distance);
1683 }
1684
1685 /**
1686 * Returns the value obtained by rotating the two's complement binary
1687 * representation of the specified {@code int} value right by the
1688 * specified number of bits. (Bits shifted out of the right hand, or
1689 * low-order, side reenter on the left, or high-order.)
1690 *
1691 * <p>Note that right rotation with a negative distance is equivalent to
1692 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
1693 * distance)}. Note also that rotation by any multiple of 32 is a
1694 * no-op, so all but the last five bits of the rotation distance can be
1695 * ignored, even if the distance is negative: {@code rotateRight(val,
1696 * distance) == rotateRight(val, distance & 0x1F)}.
1697 *
1698 * @param i the value whose bits are to be rotated right
1699 * @param distance the number of bit positions to rotate right
1700 * @return the value obtained by rotating the two's complement binary
1701 * representation of the specified {@code int} value right by the
1702 * specified number of bits.
1703 * @since 1.5
1704 */
1705 public static int rotateRight(int i, int distance) {
1706 return (i >>> distance) | (i << -distance);
1707 }
1708
1709 /**
1710 * Returns the value obtained by reversing the order of the bits in the
1711 * two's complement binary representation of the specified {@code int}
1712 * value.
1713 *
1714 * @param i the value to be reversed
1715 * @return the value obtained by reversing order of the bits in the
1716 * specified {@code int} value.
1717 * @since 1.5
1718 */
1719 public static int reverse(int i) {
1720 // HD, Figure 7-1
1721 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
1722 i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
1723 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
1724 i = (i << 24) | ((i & 0xff00) << 8) |
1725 ((i >>> 8) & 0xff00) | (i >>> 24);
1726 return i;
1727 }
1728
1729 /**
1730 * Returns the signum function of the specified {@code int} value. (The
1731 * return value is -1 if the specified value is negative; 0 if the
1732 * specified value is zero; and 1 if the specified value is positive.)
1733 *
1734 * @param i the value whose signum is to be computed
1735 * @return the signum function of the specified {@code int} value.
1736 * @since 1.5
1737 */
1738 public static int signum(int i) {
1739 // HD, Section 2-7
1740 return (i >> 31) | (-i >>> 31);
1741 }
1742
1743 /**
1744 * Returns the value obtained by reversing the order of the bytes in the
1745 * two's complement representation of the specified {@code int} value.
1746 *
1747 * @param i the value whose bytes are to be reversed
1748 * @return the value obtained by reversing the bytes in the specified
1749 * {@code int} value.
1750 * @since 1.5
1751 */
1752 public static int reverseBytes(int i) {
1753 return ((i >>> 24) ) |
1754 ((i >> 8) & 0xFF00) |
1755 ((i << 8) & 0xFF0000) |
1756 ((i << 24));
1757 }
1758
1759 /**
1760 * Adds two integers together as per the + operator.
1761 *
1762 * @param a the first operand
1763 * @param b the second operand
1764 * @return the sum of {@code a} and {@code b}
1765 * @see java.util.function.BinaryOperator
1766 * @since 1.8
1767 */
1768 public static int sum(int a, int b) {
1769 return a + b;
1770 }
1771
1772 /**
1773 * Returns the greater of two {@code int} values
1774 * as if by calling {@link Math#max(int, int) Math.max}.
1775 *
1776 * @param a the first operand
1777 * @param b the second operand
1778 * @return the greater of {@code a} and {@code b}
1779 * @see java.util.function.BinaryOperator
1780 * @since 1.8
1781 */
1782 public static int max(int a, int b) {
1783 return Math.max(a, b);
1784 }
1785
1786 /**
1787 * Returns the smaller of two {@code int} values
1788 * as if by calling {@link Math#min(int, int) Math.min}.
1789 *
1790 * @param a the first operand
1791 * @param b the second operand
1792 * @return the smaller of {@code a} and {@code b}
1793 * @see java.util.function.BinaryOperator
1794 * @since 1.8
1795 */
1796 public static int min(int a, int b) {
1797 return Math.min(a, b);
1798 }
1799
1800 /** use serialVersionUID from JDK 1.0.2 for interoperability */
1801 @Native private static final long serialVersionUID = 1360826667806852920L;
1802 }