1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36 package java.util.concurrent;
37
38 import java.io.ObjectStreamField;
39 import java.util.Random;
40 import java.util.Spliterator;
41 import java.util.concurrent.atomic.AtomicInteger;
42 import java.util.concurrent.atomic.AtomicLong;
43 import java.util.function.DoubleConsumer;
44 import java.util.function.IntConsumer;
45 import java.util.function.LongConsumer;
46 import java.util.stream.DoubleStream;
47 import java.util.stream.IntStream;
48 import java.util.stream.LongStream;
49 import java.util.stream.StreamSupport;
50 import sun.misc.VM;
51
52 /**
53 * A random number generator isolated to the current thread. Like the
54 * global {@link java.util.Random} generator used by the {@link
55 * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized
56 * with an internally generated seed that may not otherwise be
57 * modified. When applicable, use of {@code ThreadLocalRandom} rather
58 * than shared {@code Random} objects in concurrent programs will
59 * typically encounter much less overhead and contention. Use of
60 * {@code ThreadLocalRandom} is particularly appropriate when multiple
61 * tasks (for example, each a {@link ForkJoinTask}) use random numbers
62 * in parallel in thread pools.
63 *
64 * <p>Usages of this class should typically be of the form:
65 * {@code ThreadLocalRandom.current().nextX(...)} (where
66 * {@code X} is {@code Int}, {@code Long}, etc).
67 * When all usages are of this form, it is never possible to
68 * accidently share a {@code ThreadLocalRandom} across multiple threads.
69 *
70 * <p>This class also provides additional commonly used bounded random
71 * generation methods.
72 *
73 * <p>Instances of {@code ThreadLocalRandom} are not cryptographically
74 * secure. Consider instead using {@link java.security.SecureRandom}
75 * in security-sensitive applications. Additionally,
76 * default-constructed instances do not use a cryptographically random
77 * seed unless the {@linkplain System#getProperty system property}
78 * {@code java.util.secureRandomSeed} is set to {@code true}.
79 *
80 * @since 1.7
81 * @author Doug Lea
82 */
83 public class ThreadLocalRandom extends Random {
84 /*
85 * This class implements the java.util.Random API (and subclasses
86 * Random) using a single static instance that accesses random
87 * number state held in class Thread (primarily, field
88 * threadLocalRandomSeed). In doing so, it also provides a home
89 * for managing package-private utilities that rely on exactly the
90 * same state as needed to maintain the ThreadLocalRandom
91 * instances. We leverage the need for an initialization flag
92 * field to also use it as a "probe" -- a self-adjusting thread
93 * hash used for contention avoidance, as well as a secondary
94 * simpler (xorShift) random seed that is conservatively used to
95 * avoid otherwise surprising users by hijacking the
96 * ThreadLocalRandom sequence. The dual use is a marriage of
97 * convenience, but is a simple and efficient way of reducing
98 * application-level overhead and footprint of most concurrent
99 * programs.
100 *
101 * Even though this class subclasses java.util.Random, it uses the
102 * same basic algorithm as java.util.SplittableRandom. (See its
103 * internal documentation for explanations, which are not repeated
104 * here.) Because ThreadLocalRandoms are not splittable
105 * though, we use only a single 64bit gamma.
106 *
107 * Because this class is in a different package than class Thread,
108 * field access methods use Unsafe to bypass access control rules.
109 * To conform to the requirements of the Random superclass
110 * constructor, the common static ThreadLocalRandom maintains an
111 * "initialized" field for the sake of rejecting user calls to
112 * setSeed while still allowing a call from constructor. Note
113 * that serialization is completely unnecessary because there is
114 * only a static singleton. But we generate a serial form
115 * containing "rnd" and "initialized" fields to ensure
116 * compatibility across versions.
117 *
118 * Implementations of non-core methods are mostly the same as in
119 * SplittableRandom, that were in part derived from a previous
120 * version of this class.
121 *
122 * The nextLocalGaussian ThreadLocal supports the very rarely used
123 * nextGaussian method by providing a holder for the second of a
124 * pair of them. As is true for the base class version of this
125 * method, this time/space tradeoff is probably never worthwhile,
126 * but we provide identical statistical properties.
127 */
128
129 /** Generates per-thread initialization/probe field */
130 private static final AtomicInteger probeGenerator =
131 new AtomicInteger();
132
133 /**
134 * The next seed for default constructors.
135 */
136 private static final AtomicLong seeder = new AtomicLong(initialSeed());
137
138 private static long initialSeed() {
139 String sec = VM.getSavedProperty("java.util.secureRandomSeed");
140 if (Boolean.parseBoolean(sec)) {
141 byte[] seedBytes = java.security.SecureRandom.getSeed(8);
142 long s = (long)(seedBytes[0]) & 0xffL;
143 for (int i = 1; i < 8; ++i)
144 s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
145 return s;
146 }
147 return (mix64(System.currentTimeMillis()) ^
148 mix64(System.nanoTime()));
149 }
150
151 /**
152 * The seed increment
153 */
154 private static final long GAMMA = 0x9e3779b97f4a7c15L;
155
156 /**
157 * The increment for generating probe values
158 */
159 private static final int PROBE_INCREMENT = 0x9e3779b9;
160
161 /**
162 * The increment of seeder per new instance
163 */
164 private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL;
165
166 // Constants from SplittableRandom
167 private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
168 private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << 24)
169
170 /** Rarely-used holder for the second of a pair of Gaussians */
171 private static final ThreadLocal<Double> nextLocalGaussian =
172 new ThreadLocal<Double>();
173
174 private static long mix64(long z) {
175 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
176 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
177 return z ^ (z >>> 33);
178 }
179
180 private static int mix32(long z) {
181 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
182 return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
183 }
184
185 /**
186 * Field used only during singleton initialization.
187 * True when constructor completes.
188 */
189 boolean initialized;
190
191 /** Constructor used only for static singleton */
192 private ThreadLocalRandom() {
193 initialized = true; // false during super() call
194 }
195
196 /** The common ThreadLocalRandom */
197 static final ThreadLocalRandom instance = new ThreadLocalRandom();
198
199 /**
200 * Initialize Thread fields for the current thread. Called only
201 * when Thread.threadLocalRandomProbe is zero, indicating that a
202 * thread local seed value needs to be generated. Note that even
203 * though the initialization is purely thread-local, we need to
204 * rely on (static) atomic generators to initialize the values.
205 */
206 static final void localInit() {
207 int p = probeGenerator.addAndGet(PROBE_INCREMENT);
208 int probe = (p == 0) ? 1 : p; // skip 0
209 long seed = mix64(seeder.getAndAdd(SEEDER_INCREMENT));
210 Thread t = Thread.currentThread();
211 UNSAFE.putLong(t, SEED, seed);
212 UNSAFE.putInt(t, PROBE, probe);
213 }
214
215 /**
216 * Returns the current thread's {@code ThreadLocalRandom}.
217 *
218 * @return the current thread's {@code ThreadLocalRandom}
219 */
220 public static ThreadLocalRandom current() {
221 if (UNSAFE.getInt(Thread.currentThread(), PROBE) == 0)
222 localInit();
223 return instance;
224 }
225
226 /**
227 * Throws {@code UnsupportedOperationException}. Setting seeds in
228 * this generator is not supported.
229 *
230 * @throws UnsupportedOperationException always
231 */
232 public void setSeed(long seed) {
233 // only allow call from super() constructor
234 if (initialized)
235 throw new UnsupportedOperationException();
236 }
237
238 final long nextSeed() {
239 Thread t; long r; // read and update per-thread seed
240 UNSAFE.putLong(t = Thread.currentThread(), SEED,
241 r = UNSAFE.getLong(t, SEED) + GAMMA);
242 return r;
243 }
244
245 // We must define this, but never use it.
246 protected int next(int bits) {
247 return (int)(mix64(nextSeed()) >>> (64 - bits));
248 }
249
250 // IllegalArgumentException messages
251 static final String BadBound = "bound must be positive";
252 static final String BadRange = "bound must be greater than origin";
253 static final String BadSize = "size must be non-negative";
254
255 /**
256 * The form of nextLong used by LongStream Spliterators. If
257 * origin is greater than bound, acts as unbounded form of
258 * nextLong, else as bounded form.
259 *
260 * @param origin the least value, unless greater than bound
261 * @param bound the upper bound (exclusive), must not equal origin
262 * @return a pseudorandom value
263 */
264 final long internalNextLong(long origin, long bound) {
265 long r = mix64(nextSeed());
266 if (origin < bound) {
267 long n = bound - origin, m = n - 1;
268 if ((n & m) == 0L) // power of two
269 r = (r & m) + origin;
270 else if (n > 0L) { // reject over-represented candidates
271 for (long u = r >>> 1; // ensure nonnegative
272 u + m - (r = u % n) < 0L; // rejection check
273 u = mix64(nextSeed()) >>> 1) // retry
274 ;
275 r += origin;
276 }
277 else { // range not representable as long
278 while (r < origin || r >= bound)
279 r = mix64(nextSeed());
280 }
281 }
282 return r;
283 }
284
285 /**
286 * The form of nextInt used by IntStream Spliterators.
287 * Exactly the same as long version, except for types.
288 *
289 * @param origin the least value, unless greater than bound
290 * @param bound the upper bound (exclusive), must not equal origin
291 * @return a pseudorandom value
292 */
293 final int internalNextInt(int origin, int bound) {
294 int r = mix32(nextSeed());
295 if (origin < bound) {
296 int n = bound - origin, m = n - 1;
297 if ((n & m) == 0)
298 r = (r & m) + origin;
299 else if (n > 0) {
300 for (int u = r >>> 1;
301 u + m - (r = u % n) < 0;
302 u = mix32(nextSeed()) >>> 1)
303 ;
304 r += origin;
305 }
306 else {
307 while (r < origin || r >= bound)
308 r = mix32(nextSeed());
309 }
310 }
311 return r;
312 }
313
314 /**
315 * The form of nextDouble used by DoubleStream Spliterators.
316 *
317 * @param origin the least value, unless greater than bound
318 * @param bound the upper bound (exclusive), must not equal origin
319 * @return a pseudorandom value
320 */
321 final double internalNextDouble(double origin, double bound) {
322 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
323 if (origin < bound) {
324 r = r * (bound - origin) + origin;
325 if (r >= bound) // correct for rounding
326 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
327 }
328 return r;
329 }
330
331 /**
332 * Returns a pseudorandom {@code int} value.
333 *
334 * @return a pseudorandom {@code int} value
335 */
336 public int nextInt() {
337 return mix32(nextSeed());
338 }
339
340 /**
341 * Returns a pseudorandom {@code int} value between zero (inclusive)
342 * and the specified bound (exclusive).
343 *
344 * @param bound the upper bound (exclusive). Must be positive.
345 * @return a pseudorandom {@code int} value between zero
346 * (inclusive) and the bound (exclusive)
347 * @throws IllegalArgumentException if {@code bound} is not positive
348 */
349 public int nextInt(int bound) {
350 if (bound <= 0)
351 throw new IllegalArgumentException(BadBound);
352 int r = mix32(nextSeed());
353 int m = bound - 1;
354 if ((bound & m) == 0) // power of two
355 r &= m;
356 else { // reject over-represented candidates
357 for (int u = r >>> 1;
358 u + m - (r = u % bound) < 0;
359 u = mix32(nextSeed()) >>> 1)
360 ;
361 }
362 return r;
363 }
364
365 /**
366 * Returns a pseudorandom {@code int} value between the specified
367 * origin (inclusive) and the specified bound (exclusive).
368 *
369 * @param origin the least value returned
370 * @param bound the upper bound (exclusive)
371 * @return a pseudorandom {@code int} value between the origin
372 * (inclusive) and the bound (exclusive)
373 * @throws IllegalArgumentException if {@code origin} is greater than
374 * or equal to {@code bound}
375 */
376 public int nextInt(int origin, int bound) {
377 if (origin >= bound)
378 throw new IllegalArgumentException(BadRange);
379 return internalNextInt(origin, bound);
380 }
381
382 /**
383 * Returns a pseudorandom {@code long} value.
384 *
385 * @return a pseudorandom {@code long} value
386 */
387 public long nextLong() {
388 return mix64(nextSeed());
389 }
390
391 /**
392 * Returns a pseudorandom {@code long} value between zero (inclusive)
393 * and the specified bound (exclusive).
394 *
395 * @param bound the upper bound (exclusive). Must be positive.
396 * @return a pseudorandom {@code long} value between zero
397 * (inclusive) and the bound (exclusive)
398 * @throws IllegalArgumentException if {@code bound} is not positive
399 */
400 public long nextLong(long bound) {
401 if (bound <= 0)
402 throw new IllegalArgumentException(BadBound);
403 long r = mix64(nextSeed());
404 long m = bound - 1;
405 if ((bound & m) == 0L) // power of two
406 r &= m;
407 else { // reject over-represented candidates
408 for (long u = r >>> 1;
409 u + m - (r = u % bound) < 0L;
410 u = mix64(nextSeed()) >>> 1)
411 ;
412 }
413 return r;
414 }
415
416 /**
417 * Returns a pseudorandom {@code long} value between the specified
418 * origin (inclusive) and the specified bound (exclusive).
419 *
420 * @param origin the least value returned
421 * @param bound the upper bound (exclusive)
422 * @return a pseudorandom {@code long} value between the origin
423 * (inclusive) and the bound (exclusive)
424 * @throws IllegalArgumentException if {@code origin} is greater than
425 * or equal to {@code bound}
426 */
427 public long nextLong(long origin, long bound) {
428 if (origin >= bound)
429 throw new IllegalArgumentException(BadRange);
430 return internalNextLong(origin, bound);
431 }
432
433 /**
434 * Returns a pseudorandom {@code double} value between zero
435 * (inclusive) and one (exclusive).
436 *
437 * @return a pseudorandom {@code double} value between zero
438 * (inclusive) and one (exclusive)
439 */
440 public double nextDouble() {
441 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
442 }
443
444 /**
445 * Returns a pseudorandom {@code double} value between 0.0
446 * (inclusive) and the specified bound (exclusive).
447 *
448 * @param bound the upper bound (exclusive). Must be positive.
449 * @return a pseudorandom {@code double} value between zero
450 * (inclusive) and the bound (exclusive)
451 * @throws IllegalArgumentException if {@code bound} is not positive
452 */
453 public double nextDouble(double bound) {
454 if (!(bound > 0.0))
455 throw new IllegalArgumentException(BadBound);
456 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
457 return (result < bound) ? result : // correct for rounding
458 Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
459 }
460
461 /**
462 * Returns a pseudorandom {@code double} value between the specified
463 * origin (inclusive) and bound (exclusive).
464 *
465 * @param origin the least value returned
466 * @param bound the upper bound (exclusive)
467 * @return a pseudorandom {@code double} value between the origin
468 * (inclusive) and the bound (exclusive)
469 * @throws IllegalArgumentException if {@code origin} is greater than
470 * or equal to {@code bound}
471 */
472 public double nextDouble(double origin, double bound) {
473 if (!(origin < bound))
474 throw new IllegalArgumentException(BadRange);
475 return internalNextDouble(origin, bound);
476 }
477
478 /**
479 * Returns a pseudorandom {@code boolean} value.
480 *
481 * @return a pseudorandom {@code boolean} value
482 */
483 public boolean nextBoolean() {
484 return mix32(nextSeed()) < 0;
485 }
486
487 /**
488 * Returns a pseudorandom {@code float} value between zero
489 * (inclusive) and one (exclusive).
490 *
491 * @return a pseudorandom {@code float} value between zero
492 * (inclusive) and one (exclusive)
493 */
494 public float nextFloat() {
495 return (mix32(nextSeed()) >>> 8) * FLOAT_UNIT;
496 }
497
498 public double nextGaussian() {
499 // Use nextLocalGaussian instead of nextGaussian field
500 Double d = nextLocalGaussian.get();
501 if (d != null) {
502 nextLocalGaussian.set(null);
503 return d.doubleValue();
504 }
505 double v1, v2, s;
506 do {
507 v1 = 2 * nextDouble() - 1; // between -1 and 1
508 v2 = 2 * nextDouble() - 1; // between -1 and 1
509 s = v1 * v1 + v2 * v2;
510 } while (s >= 1 || s == 0);
511 double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
512 nextLocalGaussian.set(new Double(v2 * multiplier));
513 return v1 * multiplier;
514 }
515
516 // stream methods, coded in a way intended to better isolate for
517 // maintenance purposes the small differences across forms.
518
519 /**
520 * Returns a stream producing the given {@code streamSize} number of
521 * pseudorandom {@code int} values.
522 *
523 * @param streamSize the number of values to generate
524 * @return a stream of pseudorandom {@code int} values
525 * @throws IllegalArgumentException if {@code streamSize} is
526 * less than zero
527 * @since 1.8
528 */
529 public IntStream ints(long streamSize) {
530 if (streamSize < 0L)
531 throw new IllegalArgumentException(BadSize);
532 return StreamSupport.intStream
533 (new RandomIntsSpliterator
534 (0L, streamSize, Integer.MAX_VALUE, 0),
535 false);
536 }
537
538 /**
539 * Returns an effectively unlimited stream of pseudorandom {@code int}
540 * values.
541 *
542 * @implNote This method is implemented to be equivalent to {@code
543 * ints(Long.MAX_VALUE)}.
544 *
545 * @return a stream of pseudorandom {@code int} values
546 * @since 1.8
547 */
548 public IntStream ints() {
549 return StreamSupport.intStream
550 (new RandomIntsSpliterator
551 (0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
552 false);
553 }
554
555 /**
556 * Returns a stream producing the given {@code streamSize} number
557 * of pseudorandom {@code int} values, each conforming to the given
558 * origin (inclusive) and bound (exclusive).
559 *
560 * @param streamSize the number of values to generate
561 * @param randomNumberOrigin the origin (inclusive) of each random value
562 * @param randomNumberBound the bound (exclusive) of each random value
563 * @return a stream of pseudorandom {@code int} values,
564 * each with the given origin (inclusive) and bound (exclusive)
565 * @throws IllegalArgumentException if {@code streamSize} is
566 * less than zero, or {@code randomNumberOrigin}
567 * is greater than or equal to {@code randomNumberBound}
568 * @since 1.8
569 */
570 public IntStream ints(long streamSize, int randomNumberOrigin,
571 int randomNumberBound) {
572 if (streamSize < 0L)
573 throw new IllegalArgumentException(BadSize);
574 if (randomNumberOrigin >= randomNumberBound)
575 throw new IllegalArgumentException(BadRange);
576 return StreamSupport.intStream
577 (new RandomIntsSpliterator
578 (0L, streamSize, randomNumberOrigin, randomNumberBound),
579 false);
580 }
581
582 /**
583 * Returns an effectively unlimited stream of pseudorandom {@code
584 * int} values, each conforming to the given origin (inclusive) and bound
585 * (exclusive).
586 *
587 * @implNote This method is implemented to be equivalent to {@code
588 * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
589 *
590 * @param randomNumberOrigin the origin (inclusive) of each random value
591 * @param randomNumberBound the bound (exclusive) of each random value
592 * @return a stream of pseudorandom {@code int} values,
593 * each with the given origin (inclusive) and bound (exclusive)
594 * @throws IllegalArgumentException if {@code randomNumberOrigin}
595 * is greater than or equal to {@code randomNumberBound}
596 * @since 1.8
597 */
598 public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
599 if (randomNumberOrigin >= randomNumberBound)
600 throw new IllegalArgumentException(BadRange);
601 return StreamSupport.intStream
602 (new RandomIntsSpliterator
603 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
604 false);
605 }
606
607 /**
608 * Returns a stream producing the given {@code streamSize} number of
609 * pseudorandom {@code long} values.
610 *
611 * @param streamSize the number of values to generate
612 * @return a stream of pseudorandom {@code long} values
613 * @throws IllegalArgumentException if {@code streamSize} is
614 * less than zero
615 * @since 1.8
616 */
617 public LongStream longs(long streamSize) {
618 if (streamSize < 0L)
619 throw new IllegalArgumentException(BadSize);
620 return StreamSupport.longStream
621 (new RandomLongsSpliterator
622 (0L, streamSize, Long.MAX_VALUE, 0L),
623 false);
624 }
625
626 /**
627 * Returns an effectively unlimited stream of pseudorandom {@code long}
628 * values.
629 *
630 * @implNote This method is implemented to be equivalent to {@code
631 * longs(Long.MAX_VALUE)}.
632 *
633 * @return a stream of pseudorandom {@code long} values
634 * @since 1.8
635 */
636 public LongStream longs() {
637 return StreamSupport.longStream
638 (new RandomLongsSpliterator
639 (0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
640 false);
641 }
642
643 /**
644 * Returns a stream producing the given {@code streamSize} number of
645 * pseudorandom {@code long}, each conforming to the given origin
646 * (inclusive) and bound (exclusive).
647 *
648 * @param streamSize the number of values to generate
649 * @param randomNumberOrigin the origin (inclusive) of each random value
650 * @param randomNumberBound the bound (exclusive) of each random value
651 * @return a stream of pseudorandom {@code long} values,
652 * each with the given origin (inclusive) and bound (exclusive)
653 * @throws IllegalArgumentException if {@code streamSize} is
654 * less than zero, or {@code randomNumberOrigin}
655 * is greater than or equal to {@code randomNumberBound}
656 * @since 1.8
657 */
658 public LongStream longs(long streamSize, long randomNumberOrigin,
659 long randomNumberBound) {
660 if (streamSize < 0L)
661 throw new IllegalArgumentException(BadSize);
662 if (randomNumberOrigin >= randomNumberBound)
663 throw new IllegalArgumentException(BadRange);
664 return StreamSupport.longStream
665 (new RandomLongsSpliterator
666 (0L, streamSize, randomNumberOrigin, randomNumberBound),
667 false);
668 }
669
670 /**
671 * Returns an effectively unlimited stream of pseudorandom {@code
672 * long} values, each conforming to the given origin (inclusive) and bound
673 * (exclusive).
674 *
675 * @implNote This method is implemented to be equivalent to {@code
676 * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
677 *
678 * @param randomNumberOrigin the origin (inclusive) of each random value
679 * @param randomNumberBound the bound (exclusive) of each random value
680 * @return a stream of pseudorandom {@code long} values,
681 * each with the given origin (inclusive) and bound (exclusive)
682 * @throws IllegalArgumentException if {@code randomNumberOrigin}
683 * is greater than or equal to {@code randomNumberBound}
684 * @since 1.8
685 */
686 public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
687 if (randomNumberOrigin >= randomNumberBound)
688 throw new IllegalArgumentException(BadRange);
689 return StreamSupport.longStream
690 (new RandomLongsSpliterator
691 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
692 false);
693 }
694
695 /**
696 * Returns a stream producing the given {@code streamSize} number of
697 * pseudorandom {@code double} values, each between zero
698 * (inclusive) and one (exclusive).
699 *
700 * @param streamSize the number of values to generate
701 * @return a stream of {@code double} values
702 * @throws IllegalArgumentException if {@code streamSize} is
703 * less than zero
704 * @since 1.8
705 */
706 public DoubleStream doubles(long streamSize) {
707 if (streamSize < 0L)
708 throw new IllegalArgumentException(BadSize);
709 return StreamSupport.doubleStream
710 (new RandomDoublesSpliterator
711 (0L, streamSize, Double.MAX_VALUE, 0.0),
712 false);
713 }
714
715 /**
716 * Returns an effectively unlimited stream of pseudorandom {@code
717 * double} values, each between zero (inclusive) and one
718 * (exclusive).
719 *
720 * @implNote This method is implemented to be equivalent to {@code
721 * doubles(Long.MAX_VALUE)}.
722 *
723 * @return a stream of pseudorandom {@code double} values
724 * @since 1.8
725 */
726 public DoubleStream doubles() {
727 return StreamSupport.doubleStream
728 (new RandomDoublesSpliterator
729 (0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
730 false);
731 }
732
733 /**
734 * Returns a stream producing the given {@code streamSize} number of
735 * pseudorandom {@code double} values, each conforming to the given origin
736 * (inclusive) and bound (exclusive).
737 *
738 * @param streamSize the number of values to generate
739 * @param randomNumberOrigin the origin (inclusive) of each random value
740 * @param randomNumberBound the bound (exclusive) of each random value
741 * @return a stream of pseudorandom {@code double} values,
742 * each with the given origin (inclusive) and bound (exclusive)
743 * @throws IllegalArgumentException if {@code streamSize} is
744 * less than zero
745 * @throws IllegalArgumentException if {@code randomNumberOrigin}
746 * is greater than or equal to {@code randomNumberBound}
747 * @since 1.8
748 */
749 public DoubleStream doubles(long streamSize, double randomNumberOrigin,
750 double randomNumberBound) {
751 if (streamSize < 0L)
752 throw new IllegalArgumentException(BadSize);
753 if (!(randomNumberOrigin < randomNumberBound))
754 throw new IllegalArgumentException(BadRange);
755 return StreamSupport.doubleStream
756 (new RandomDoublesSpliterator
757 (0L, streamSize, randomNumberOrigin, randomNumberBound),
758 false);
759 }
760
761 /**
762 * Returns an effectively unlimited stream of pseudorandom {@code
763 * double} values, each conforming to the given origin (inclusive) and bound
764 * (exclusive).
765 *
766 * @implNote This method is implemented to be equivalent to {@code
767 * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
768 *
769 * @param randomNumberOrigin the origin (inclusive) of each random value
770 * @param randomNumberBound the bound (exclusive) of each random value
771 * @return a stream of pseudorandom {@code double} values,
772 * each with the given origin (inclusive) and bound (exclusive)
773 * @throws IllegalArgumentException if {@code randomNumberOrigin}
774 * is greater than or equal to {@code randomNumberBound}
775 * @since 1.8
776 */
777 public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
778 if (!(randomNumberOrigin < randomNumberBound))
779 throw new IllegalArgumentException(BadRange);
780 return StreamSupport.doubleStream
781 (new RandomDoublesSpliterator
782 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
783 false);
784 }
785
786 /**
787 * Spliterator for int streams. We multiplex the four int
788 * versions into one class by treating a bound less than origin as
789 * unbounded, and also by treating "infinite" as equivalent to
790 * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
791 * approach. The long and double versions of this class are
792 * identical except for types.
793 */
794 static final class RandomIntsSpliterator implements Spliterator.OfInt {
795 long index;
796 final long fence;
797 final int origin;
798 final int bound;
799 RandomIntsSpliterator(long index, long fence,
800 int origin, int bound) {
801 this.index = index; this.fence = fence;
802 this.origin = origin; this.bound = bound;
803 }
804
805 public RandomIntsSpliterator trySplit() {
806 long i = index, m = (i + fence) >>> 1;
807 return (m <= i) ? null :
808 new RandomIntsSpliterator(i, index = m, origin, bound);
809 }
810
811 public long estimateSize() {
812 return fence - index;
813 }
814
815 public int characteristics() {
816 return (Spliterator.SIZED | Spliterator.SUBSIZED |
817 Spliterator.NONNULL | Spliterator.IMMUTABLE);
818 }
819
820 public boolean tryAdvance(IntConsumer consumer) {
821 if (consumer == null) throw new NullPointerException();
822 long i = index, f = fence;
823 if (i < f) {
824 consumer.accept(ThreadLocalRandom.current().internalNextInt(origin, bound));
825 index = i + 1;
826 return true;
827 }
828 return false;
829 }
830
831 public void forEachRemaining(IntConsumer consumer) {
832 if (consumer == null) throw new NullPointerException();
833 long i = index, f = fence;
834 if (i < f) {
835 index = f;
836 int o = origin, b = bound;
837 ThreadLocalRandom rng = ThreadLocalRandom.current();
838 do {
839 consumer.accept(rng.internalNextInt(o, b));
840 } while (++i < f);
841 }
842 }
843 }
844
845 /**
846 * Spliterator for long streams.
847 */
848 static final class RandomLongsSpliterator implements Spliterator.OfLong {
849 long index;
850 final long fence;
851 final long origin;
852 final long bound;
853 RandomLongsSpliterator(long index, long fence,
854 long origin, long bound) {
855 this.index = index; this.fence = fence;
856 this.origin = origin; this.bound = bound;
857 }
858
859 public RandomLongsSpliterator trySplit() {
860 long i = index, m = (i + fence) >>> 1;
861 return (m <= i) ? null :
862 new RandomLongsSpliterator(i, index = m, origin, bound);
863 }
864
865 public long estimateSize() {
866 return fence - index;
867 }
868
869 public int characteristics() {
870 return (Spliterator.SIZED | Spliterator.SUBSIZED |
871 Spliterator.NONNULL | Spliterator.IMMUTABLE);
872 }
873
874 public boolean tryAdvance(LongConsumer consumer) {
875 if (consumer == null) throw new NullPointerException();
876 long i = index, f = fence;
877 if (i < f) {
878 consumer.accept(ThreadLocalRandom.current().internalNextLong(origin, bound));
879 index = i + 1;
880 return true;
881 }
882 return false;
883 }
884
885 public void forEachRemaining(LongConsumer consumer) {
886 if (consumer == null) throw new NullPointerException();
887 long i = index, f = fence;
888 if (i < f) {
889 index = f;
890 long o = origin, b = bound;
891 ThreadLocalRandom rng = ThreadLocalRandom.current();
892 do {
893 consumer.accept(rng.internalNextLong(o, b));
894 } while (++i < f);
895 }
896 }
897
898 }
899
900 /**
901 * Spliterator for double streams.
902 */
903 static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
904 long index;
905 final long fence;
906 final double origin;
907 final double bound;
908 RandomDoublesSpliterator(long index, long fence,
909 double origin, double bound) {
910 this.index = index; this.fence = fence;
911 this.origin = origin; this.bound = bound;
912 }
913
914 public RandomDoublesSpliterator trySplit() {
915 long i = index, m = (i + fence) >>> 1;
916 return (m <= i) ? null :
917 new RandomDoublesSpliterator(i, index = m, origin, bound);
918 }
919
920 public long estimateSize() {
921 return fence - index;
922 }
923
924 public int characteristics() {
925 return (Spliterator.SIZED | Spliterator.SUBSIZED |
926 Spliterator.NONNULL | Spliterator.IMMUTABLE);
927 }
928
929 public boolean tryAdvance(DoubleConsumer consumer) {
930 if (consumer == null) throw new NullPointerException();
931 long i = index, f = fence;
932 if (i < f) {
933 consumer.accept(ThreadLocalRandom.current().internalNextDouble(origin, bound));
934 index = i + 1;
935 return true;
936 }
937 return false;
938 }
939
940 public void forEachRemaining(DoubleConsumer consumer) {
941 if (consumer == null) throw new NullPointerException();
942 long i = index, f = fence;
943 if (i < f) {
944 index = f;
945 double o = origin, b = bound;
946 ThreadLocalRandom rng = ThreadLocalRandom.current();
947 do {
948 consumer.accept(rng.internalNextDouble(o, b));
949 } while (++i < f);
950 }
951 }
952 }
953
954
955 // Within-package utilities
956
957 /*
958 * Descriptions of the usages of the methods below can be found in
959 * the classes that use them. Briefly, a thread's "probe" value is
960 * a non-zero hash code that (probably) does not collide with
961 * other existing threads with respect to any power of two
962 * collision space. When it does collide, it is pseudo-randomly
963 * adjusted (using a Marsaglia XorShift). The nextSecondarySeed
964 * method is used in the same contexts as ThreadLocalRandom, but
965 * only for transient usages such as random adaptive spin/block
966 * sequences for which a cheap RNG suffices and for which it could
967 * in principle disrupt user-visible statistical properties of the
968 * main ThreadLocalRandom if we were to use it.
969 *
970 * Note: Because of package-protection issues, versions of some
971 * these methods also appear in some subpackage classes.
972 */
973
974 /**
975 * Returns the probe value for the current thread without forcing
976 * initialization. Note that invoking ThreadLocalRandom.current()
977 * can be used to force initialization on zero return.
978 */
979 static final int getProbe() {
980 return UNSAFE.getInt(Thread.currentThread(), PROBE);
981 }
982
983 /**
984 * Pseudo-randomly advances and records the given probe value for the
985 * given thread.
986 */
987 static final int advanceProbe(int probe) {
988 probe ^= probe << 13; // xorshift
989 probe ^= probe >>> 17;
990 probe ^= probe << 5;
991 UNSAFE.putInt(Thread.currentThread(), PROBE, probe);
992 return probe;
993 }
994
995 /**
996 * Returns the pseudo-randomly initialized or updated secondary seed.
997 */
998 static final int nextSecondarySeed() {
999 int r;
1000 Thread t = Thread.currentThread();
1001 if ((r = UNSAFE.getInt(t, SECONDARY)) != 0) {
1002 r ^= r << 13; // xorshift
1003 r ^= r >>> 17;
1004 r ^= r << 5;
1005 }
1006 else {
1007 localInit();
1008 if ((r = (int)UNSAFE.getLong(t, SEED)) == 0)
1009 r = 1; // avoid zero
1010 }
1011 UNSAFE.putInt(t, SECONDARY, r);
1012 return r;
1013 }
1014
1015 // Serialization support
1016
1017 private static final long serialVersionUID = -5851777807851030925L;
1018
1019 /**
1020 * @serialField rnd long
1021 * seed for random computations
1022 * @serialField initialized boolean
1023 * always true
1024 */
1025 private static final ObjectStreamField[] serialPersistentFields = {
1026 new ObjectStreamField("rnd", long.class),
1027 new ObjectStreamField("initialized", boolean.class),
1028 };
1029
1030 /**
1031 * Saves the {@code ThreadLocalRandom} to a stream (that is, serializes it).
1032 * @param s the stream
1033 * @throws java.io.IOException if an I/O error occurs
1034 */
1035 private void writeObject(java.io.ObjectOutputStream s)
1036 throws java.io.IOException {
1037
1038 java.io.ObjectOutputStream.PutField fields = s.putFields();
1039 fields.put("rnd", UNSAFE.getLong(Thread.currentThread(), SEED));
1040 fields.put("initialized", true);
1041 s.writeFields();
1042 }
1043
1044 /**
1045 * Returns the {@link #current() current} thread's {@code ThreadLocalRandom}.
1046 * @return the {@link #current() current} thread's {@code ThreadLocalRandom}
1047 */
1048 private Object readResolve() {
1049 return current();
1050 }
1051
1052 // Unsafe mechanics
1053 private static final sun.misc.Unsafe UNSAFE;
1054 private static final long SEED;
1055 private static final long PROBE;
1056 private static final long SECONDARY;
1057 static {
1058 try {
1059 UNSAFE = sun.misc.Unsafe.getUnsafe();
1060 Class<?> tk = Thread.class;
1061 SEED = UNSAFE.objectFieldOffset
1062 (tk.getDeclaredField("threadLocalRandomSeed"));
1063 PROBE = UNSAFE.objectFieldOffset
1064 (tk.getDeclaredField("threadLocalRandomProbe"));
1065 SECONDARY = UNSAFE.objectFieldOffset
1066 (tk.getDeclaredField("threadLocalRandomSecondarySeed"));
1067 } catch (Exception e) {
1068 throw new Error(e);
1069 }
1070 }
1071 }