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 sun.security.provider.SeedGenerator;
40 import java.util.Random;
41 import java.util.Spliterator;
42 import java.util.concurrent.atomic.AtomicInteger;
43 import java.util.concurrent.atomic.AtomicLong;
44 import java.util.function.DoubleConsumer;
45 import java.util.function.IntConsumer;
46 import java.util.function.LongConsumer;
47 import java.util.stream.DoubleStream;
48 import java.util.stream.IntStream;
49 import java.util.stream.LongStream;
50 import java.util.stream.StreamSupport;
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 try (SeedGenerator sg = SeedGenerator.getNativeInstance()) {
140 byte[] seedBytes = new byte[8];
141 sg.getSeedBytes(seedBytes);
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 ^ mix64(System.currentTimeMillis()) ^
146 mix64(System.nanoTime());
147 }
148 }
149
150 /**
151 * The seed increment
152 */
153 private static final long GAMMA = 0x9e3779b97f4a7c15L;
154
155 /**
156 * The increment for generating probe values
157 */
158 private static final int PROBE_INCREMENT = 0x9e3779b9;
159
160 /**
161 * The increment of seeder per new instance
162 */
163 private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL;
164
165 // Constants from SplittableRandom
166 private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
167 private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << 24)
168
169 /** Rarely-used holder for the second of a pair of Gaussians */
170 private static final ThreadLocal<Double> nextLocalGaussian =
171 new ThreadLocal<Double>();
172
173 private static long mix64(long z) {
174 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
175 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
176 return z ^ (z >>> 33);
177 }
178
179 private static int mix32(long z) {
180 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
181 return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
182 }
183
184 /**
185 * Field used only during singleton initialization.
186 * True when constructor completes.
187 */
188 boolean initialized;
189
190 /** Constructor used only for static singleton */
191 private ThreadLocalRandom() {
192 initialized = true; // false during super() call
193 }
194
195 /** The common ThreadLocalRandom */
196 static final ThreadLocalRandom instance = new ThreadLocalRandom();
197
198 /**
199 * Initialize Thread fields for the current thread. Called only
200 * when Thread.threadLocalRandomProbe is zero, indicating that a
201 * thread local seed value needs to be generated. Note that even
202 * though the initialization is purely thread-local, we need to
203 * rely on (static) atomic generators to initialize the values.
204 */
205 static final void localInit() {
206 int p = probeGenerator.addAndGet(PROBE_INCREMENT);
207 int probe = (p == 0) ? 1 : p; // skip 0
208 long seed = mix64(seeder.getAndAdd(SEEDER_INCREMENT));
209 Thread t = Thread.currentThread();
210 UNSAFE.putLong(t, SEED, seed);
211 UNSAFE.putInt(t, PROBE, probe);
212 }
213
214 /**
215 * Returns the current thread's {@code ThreadLocalRandom}.
216 *
217 * @return the current thread's {@code ThreadLocalRandom}
218 */
219 public static ThreadLocalRandom current() {
220 if (UNSAFE.getInt(Thread.currentThread(), PROBE) == 0)
221 localInit();
222 return instance;
223 }
224
225 /**
226 * Throws {@code UnsupportedOperationException}. Setting seeds in
227 * this generator is not supported.
228 *
229 * @throws UnsupportedOperationException always
230 */
231 public void setSeed(long seed) {
232 // only allow call from super() constructor
233 if (initialized)
234 throw new UnsupportedOperationException();
235 }
236
237 final long nextSeed() {
238 Thread t; long r; // read and update per-thread seed
239 UNSAFE.putLong(t = Thread.currentThread(), SEED,
240 r = UNSAFE.getLong(t, SEED) + GAMMA);
241 return r;
242 }
243
244 // We must define this, but never use it.
245 protected int next(int bits) {
246 return (int)(mix64(nextSeed()) >>> (64 - bits));
247 }
248
249 // IllegalArgumentException messages
250 static final String BadBound = "bound must be positive";
251 static final String BadRange = "bound must be greater than origin";
252 static final String BadSize = "size must be non-negative";
253
254 /**
255 * The form of nextLong used by LongStream Spliterators. If
256 * origin is greater than bound, acts as unbounded form of
257 * nextLong, else as bounded form.
258 *
259 * @param origin the least value, unless greater than bound
260 * @param bound the upper bound (exclusive), must not equal origin
261 * @return a pseudorandom value
262 */
263 final long internalNextLong(long origin, long bound) {
264 long r = mix64(nextSeed());
265 if (origin < bound) {
266 long n = bound - origin, m = n - 1;
267 if ((n & m) == 0L) // power of two
268 r = (r & m) + origin;
269 else if (n > 0L) { // reject over-represented candidates
270 for (long u = r >>> 1; // ensure nonnegative
271 u + m - (r = u % n) < 0L; // rejection check
272 u = mix64(nextSeed()) >>> 1) // retry
273 ;
274 r += origin;
275 }
276 else { // range not representable as long
277 while (r < origin || r >= bound)
278 r = mix64(nextSeed());
279 }
280 }
281 return r;
282 }
283
284 /**
285 * The form of nextInt used by IntStream Spliterators.
286 * Exactly the same as long version, except for types.
287 *
288 * @param origin the least value, unless greater than bound
289 * @param bound the upper bound (exclusive), must not equal origin
290 * @return a pseudorandom value
291 */
292 final int internalNextInt(int origin, int bound) {
293 int r = mix32(nextSeed());
294 if (origin < bound) {
295 int n = bound - origin, m = n - 1;
296 if ((n & m) == 0)
297 r = (r & m) + origin;
298 else if (n > 0) {
299 for (int u = r >>> 1;
300 u + m - (r = u % n) < 0;
301 u = mix32(nextSeed()) >>> 1)
302 ;
303 r += origin;
304 }
305 else {
306 while (r < origin || r >= bound)
307 r = mix32(nextSeed());
308 }
309 }
310 return r;
311 }
312
313 /**
314 * The form of nextDouble used by DoubleStream Spliterators.
315 *
316 * @param origin the least value, unless greater than bound
317 * @param bound the upper bound (exclusive), must not equal origin
318 * @return a pseudorandom value
319 */
320 final double internalNextDouble(double origin, double bound) {
321 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
322 if (origin < bound) {
323 r = r * (bound - origin) + origin;
324 if (r >= bound) // correct for rounding
325 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
326 }
327 return r;
328 }
329
330 /**
331 * Returns a pseudorandom {@code int} value.
332 *
333 * @return a pseudorandom {@code int} value
334 */
335 public int nextInt() {
336 return mix32(nextSeed());
337 }
338
339 /**
340 * Returns a pseudorandom {@code int} value between zero (inclusive)
341 * and the specified bound (exclusive).
342 *
343 * @param bound the upper bound (exclusive). Must be positive.
344 * @return a pseudorandom {@code int} value between zero
345 * (inclusive) and the bound (exclusive)
346 * @throws IllegalArgumentException if {@code bound} is not positive
347 */
348 public int nextInt(int bound) {
349 if (bound <= 0)
350 throw new IllegalArgumentException(BadBound);
351 int r = mix32(nextSeed());
352 int m = bound - 1;
353 if ((bound & m) == 0) // power of two
354 r &= m;
355 else { // reject over-represented candidates
356 for (int u = r >>> 1;
357 u + m - (r = u % bound) < 0;
358 u = mix32(nextSeed()) >>> 1)
359 ;
360 }
361 return r;
362 }
363
364 /**
365 * Returns a pseudorandom {@code int} value between the specified
366 * origin (inclusive) and the specified bound (exclusive).
367 *
368 * @param origin the least value returned
369 * @param bound the upper bound (exclusive)
370 * @return a pseudorandom {@code int} value between the origin
371 * (inclusive) and the bound (exclusive)
372 * @throws IllegalArgumentException if {@code origin} is greater than
373 * or equal to {@code bound}
374 */
375 public int nextInt(int origin, int bound) {
376 if (origin >= bound)
377 throw new IllegalArgumentException(BadRange);
378 return internalNextInt(origin, bound);
379 }
380
381 /**
382 * Returns a pseudorandom {@code long} value.
383 *
384 * @return a pseudorandom {@code long} value
385 */
386 public long nextLong() {
387 return mix64(nextSeed());
388 }
389
390 /**
391 * Returns a pseudorandom {@code long} value between zero (inclusive)
392 * and the specified bound (exclusive).
393 *
394 * @param bound the upper bound (exclusive). Must be positive.
395 * @return a pseudorandom {@code long} value between zero
396 * (inclusive) and the bound (exclusive)
397 * @throws IllegalArgumentException if {@code bound} is not positive
398 */
399 public long nextLong(long bound) {
400 if (bound <= 0)
401 throw new IllegalArgumentException(BadBound);
402 long r = mix64(nextSeed());
403 long m = bound - 1;
404 if ((bound & m) == 0L) // power of two
405 r &= m;
406 else { // reject over-represented candidates
407 for (long u = r >>> 1;
408 u + m - (r = u % bound) < 0L;
409 u = mix64(nextSeed()) >>> 1)
410 ;
411 }
412 return r;
413 }
414
415 /**
416 * Returns a pseudorandom {@code long} value between the specified
417 * origin (inclusive) and the specified bound (exclusive).
418 *
419 * @param origin the least value returned
420 * @param bound the upper bound (exclusive)
421 * @return a pseudorandom {@code long} value between the origin
422 * (inclusive) and the bound (exclusive)
423 * @throws IllegalArgumentException if {@code origin} is greater than
424 * or equal to {@code bound}
425 */
426 public long nextLong(long origin, long bound) {
427 if (origin >= bound)
428 throw new IllegalArgumentException(BadRange);
429 return internalNextLong(origin, bound);
430 }
431
432 /**
433 * Returns a pseudorandom {@code double} value between zero
434 * (inclusive) and one (exclusive).
435 *
436 * @return a pseudorandom {@code double} value between zero
437 * (inclusive) and one (exclusive)
438 */
439 public double nextDouble() {
440 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
441 }
442
443 /**
444 * Returns a pseudorandom {@code double} value between 0.0
445 * (inclusive) and the specified bound (exclusive).
446 *
447 * @param bound the upper bound (exclusive). Must be positive.
448 * @return a pseudorandom {@code double} value between zero
449 * (inclusive) and the bound (exclusive)
450 * @throws IllegalArgumentException if {@code bound} is not positive
451 */
452 public double nextDouble(double bound) {
453 if (!(bound > 0.0))
454 throw new IllegalArgumentException(BadBound);
455 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
456 return (result < bound) ? result : // correct for rounding
457 Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
458 }
459
460 /**
461 * Returns a pseudorandom {@code double} value between the specified
462 * origin (inclusive) and bound (exclusive).
463 *
464 * @param origin the least value returned
465 * @param bound the upper bound (exclusive)
466 * @return a pseudorandom {@code double} value between the origin
467 * (inclusive) and the bound (exclusive)
468 * @throws IllegalArgumentException if {@code origin} is greater than
469 * or equal to {@code bound}
470 */
471 public double nextDouble(double origin, double bound) {
472 if (!(origin < bound))
473 throw new IllegalArgumentException(BadRange);
474 return internalNextDouble(origin, bound);
475 }
476
477 /**
478 * Returns a pseudorandom {@code boolean} value.
479 *
480 * @return a pseudorandom {@code boolean} value
481 */
482 public boolean nextBoolean() {
483 return mix32(nextSeed()) < 0;
484 }
485
486 /**
487 * Returns a pseudorandom {@code float} value between zero
488 * (inclusive) and one (exclusive).
489 *
490 * @return a pseudorandom {@code float} value between zero
491 * (inclusive) and one (exclusive)
492 */
493 public float nextFloat() {
494 return (mix32(nextSeed()) >>> 8) * FLOAT_UNIT;
495 }
496
497 public double nextGaussian() {
498 // Use nextLocalGaussian instead of nextGaussian field
499 Double d = nextLocalGaussian.get();
500 if (d != null) {
501 nextLocalGaussian.set(null);
502 return d.doubleValue();
503 }
504 double v1, v2, s;
505 do {
506 v1 = 2 * nextDouble() - 1; // between -1 and 1
507 v2 = 2 * nextDouble() - 1; // between -1 and 1
508 s = v1 * v1 + v2 * v2;
509 } while (s >= 1 || s == 0);
510 double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
511 nextLocalGaussian.set(new Double(v2 * multiplier));
512 return v1 * multiplier;
513 }
514
515 // stream methods, coded in a way intended to better isolate for
516 // maintenance purposes the small differences across forms.
517
518 /**
519 * Returns a stream producing the given {@code streamSize} number of
520 * pseudorandom {@code int} values.
521 *
522 * @param streamSize the number of values to generate
523 * @return a stream of pseudorandom {@code int} values
524 * @throws IllegalArgumentException if {@code streamSize} is
525 * less than zero
526 * @since 1.8
527 */
528 public IntStream ints(long streamSize) {
529 if (streamSize < 0L)
530 throw new IllegalArgumentException(BadSize);
531 return StreamSupport.intStream
532 (new RandomIntsSpliterator
533 (0L, streamSize, Integer.MAX_VALUE, 0),
534 false);
535 }
536
537 /**
538 * Returns an effectively unlimited stream of pseudorandom {@code int}
539 * values.
540 *
541 * @implNote This method is implemented to be equivalent to {@code
542 * ints(Long.MAX_VALUE)}.
543 *
544 * @return a stream of pseudorandom {@code int} values
545 * @since 1.8
546 */
547 public IntStream ints() {
548 return StreamSupport.intStream
549 (new RandomIntsSpliterator
550 (0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
551 false);
552 }
553
554 /**
555 * Returns a stream producing the given {@code streamSize} number
556 * of pseudorandom {@code int} values, each conforming to the given
557 * origin (inclusive) and bound (exclusive).
558 *
559 * @param streamSize the number of values to generate
560 * @param randomNumberOrigin the origin (inclusive) of each random value
561 * @param randomNumberBound the bound (exclusive) of each random value
562 * @return a stream of pseudorandom {@code int} values,
563 * each with the given origin (inclusive) and bound (exclusive)
564 * @throws IllegalArgumentException if {@code streamSize} is
565 * less than zero, or {@code randomNumberOrigin}
566 * is greater than or equal to {@code randomNumberBound}
567 * @since 1.8
568 */
569 public IntStream ints(long streamSize, int randomNumberOrigin,
570 int randomNumberBound) {
571 if (streamSize < 0L)
572 throw new IllegalArgumentException(BadSize);
573 if (randomNumberOrigin >= randomNumberBound)
574 throw new IllegalArgumentException(BadRange);
575 return StreamSupport.intStream
576 (new RandomIntsSpliterator
577 (0L, streamSize, randomNumberOrigin, randomNumberBound),
578 false);
579 }
580
581 /**
582 * Returns an effectively unlimited stream of pseudorandom {@code
583 * int} values, each conforming to the given origin (inclusive) and bound
584 * (exclusive).
585 *
586 * @implNote This method is implemented to be equivalent to {@code
587 * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
588 *
589 * @param randomNumberOrigin the origin (inclusive) of each random value
590 * @param randomNumberBound the bound (exclusive) of each random value
591 * @return a stream of pseudorandom {@code int} values,
592 * each with the given origin (inclusive) and bound (exclusive)
593 * @throws IllegalArgumentException if {@code randomNumberOrigin}
594 * is greater than or equal to {@code randomNumberBound}
595 * @since 1.8
596 */
597 public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
598 if (randomNumberOrigin >= randomNumberBound)
599 throw new IllegalArgumentException(BadRange);
600 return StreamSupport.intStream
601 (new RandomIntsSpliterator
602 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
603 false);
604 }
605
606 /**
607 * Returns a stream producing the given {@code streamSize} number of
608 * pseudorandom {@code long} values.
609 *
610 * @param streamSize the number of values to generate
611 * @return a stream of pseudorandom {@code long} values
612 * @throws IllegalArgumentException if {@code streamSize} is
613 * less than zero
614 * @since 1.8
615 */
616 public LongStream longs(long streamSize) {
617 if (streamSize < 0L)
618 throw new IllegalArgumentException(BadSize);
619 return StreamSupport.longStream
620 (new RandomLongsSpliterator
621 (0L, streamSize, Long.MAX_VALUE, 0L),
622 false);
623 }
624
625 /**
626 * Returns an effectively unlimited stream of pseudorandom {@code long}
627 * values.
628 *
629 * @implNote This method is implemented to be equivalent to {@code
630 * longs(Long.MAX_VALUE)}.
631 *
632 * @return a stream of pseudorandom {@code long} values
633 * @since 1.8
634 */
635 public LongStream longs() {
636 return StreamSupport.longStream
637 (new RandomLongsSpliterator
638 (0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
639 false);
640 }
641
642 /**
643 * Returns a stream producing the given {@code streamSize} number of
644 * pseudorandom {@code long}, each conforming to the given origin
645 * (inclusive) and bound (exclusive).
646 *
647 * @param streamSize the number of values to generate
648 * @param randomNumberOrigin the origin (inclusive) of each random value
649 * @param randomNumberBound the bound (exclusive) of each random value
650 * @return a stream of pseudorandom {@code long} values,
651 * each with the given origin (inclusive) and bound (exclusive)
652 * @throws IllegalArgumentException if {@code streamSize} is
653 * less than zero, or {@code randomNumberOrigin}
654 * is greater than or equal to {@code randomNumberBound}
655 * @since 1.8
656 */
657 public LongStream longs(long streamSize, long randomNumberOrigin,
658 long randomNumberBound) {
659 if (streamSize < 0L)
660 throw new IllegalArgumentException(BadSize);
661 if (randomNumberOrigin >= randomNumberBound)
662 throw new IllegalArgumentException(BadRange);
663 return StreamSupport.longStream
664 (new RandomLongsSpliterator
665 (0L, streamSize, randomNumberOrigin, randomNumberBound),
666 false);
667 }
668
669 /**
670 * Returns an effectively unlimited stream of pseudorandom {@code
671 * long} values, each conforming to the given origin (inclusive) and bound
672 * (exclusive).
673 *
674 * @implNote This method is implemented to be equivalent to {@code
675 * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
676 *
677 * @param randomNumberOrigin the origin (inclusive) of each random value
678 * @param randomNumberBound the bound (exclusive) of each random value
679 * @return a stream of pseudorandom {@code long} values,
680 * each with the given origin (inclusive) and bound (exclusive)
681 * @throws IllegalArgumentException if {@code randomNumberOrigin}
682 * is greater than or equal to {@code randomNumberBound}
683 * @since 1.8
684 */
685 public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
686 if (randomNumberOrigin >= randomNumberBound)
687 throw new IllegalArgumentException(BadRange);
688 return StreamSupport.longStream
689 (new RandomLongsSpliterator
690 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
691 false);
692 }
693
694 /**
695 * Returns a stream producing the given {@code streamSize} number of
696 * pseudorandom {@code double} values, each between zero
697 * (inclusive) and one (exclusive).
698 *
699 * @param streamSize the number of values to generate
700 * @return a stream of {@code double} values
701 * @throws IllegalArgumentException if {@code streamSize} is
702 * less than zero
703 * @since 1.8
704 */
705 public DoubleStream doubles(long streamSize) {
706 if (streamSize < 0L)
707 throw new IllegalArgumentException(BadSize);
708 return StreamSupport.doubleStream
709 (new RandomDoublesSpliterator
710 (0L, streamSize, Double.MAX_VALUE, 0.0),
711 false);
712 }
713
714 /**
715 * Returns an effectively unlimited stream of pseudorandom {@code
716 * double} values, each between zero (inclusive) and one
717 * (exclusive).
718 *
719 * @implNote This method is implemented to be equivalent to {@code
720 * doubles(Long.MAX_VALUE)}.
721 *
722 * @return a stream of pseudorandom {@code double} values
723 * @since 1.8
724 */
725 public DoubleStream doubles() {
726 return StreamSupport.doubleStream
727 (new RandomDoublesSpliterator
728 (0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
729 false);
730 }
731
732 /**
733 * Returns a stream producing the given {@code streamSize} number of
734 * pseudorandom {@code double} values, each conforming to the given origin
735 * (inclusive) and bound (exclusive).
736 *
737 * @param streamSize the number of values to generate
738 * @param randomNumberOrigin the origin (inclusive) of each random value
739 * @param randomNumberBound the bound (exclusive) of each random value
740 * @return a stream of pseudorandom {@code double} values,
741 * each with the given origin (inclusive) and bound (exclusive)
742 * @throws IllegalArgumentException if {@code streamSize} is
743 * less than zero
744 * @throws IllegalArgumentException if {@code randomNumberOrigin}
745 * is greater than or equal to {@code randomNumberBound}
746 * @since 1.8
747 */
748 public DoubleStream doubles(long streamSize, double randomNumberOrigin,
749 double randomNumberBound) {
750 if (streamSize < 0L)
751 throw new IllegalArgumentException(BadSize);
752 if (!(randomNumberOrigin < randomNumberBound))
753 throw new IllegalArgumentException(BadRange);
754 return StreamSupport.doubleStream
755 (new RandomDoublesSpliterator
756 (0L, streamSize, randomNumberOrigin, randomNumberBound),
757 false);
758 }
759
760 /**
761 * Returns an effectively unlimited stream of pseudorandom {@code
762 * double} values, each conforming to the given origin (inclusive) and bound
763 * (exclusive).
764 *
765 * @implNote This method is implemented to be equivalent to {@code
766 * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
767 *
768 * @param randomNumberOrigin the origin (inclusive) of each random value
769 * @param randomNumberBound the bound (exclusive) of each random value
770 * @return a stream of pseudorandom {@code double} values,
771 * each with the given origin (inclusive) and bound (exclusive)
772 * @throws IllegalArgumentException if {@code randomNumberOrigin}
773 * is greater than or equal to {@code randomNumberBound}
774 * @since 1.8
775 */
776 public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
777 if (!(randomNumberOrigin < randomNumberBound))
778 throw new IllegalArgumentException(BadRange);
779 return StreamSupport.doubleStream
780 (new RandomDoublesSpliterator
781 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
782 false);
783 }
784
785 /**
786 * Spliterator for int streams. We multiplex the four int
787 * versions into one class by treating a bound less than origin as
788 * unbounded, and also by treating "infinite" as equivalent to
789 * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
790 * approach. The long and double versions of this class are
791 * identical except for types.
792 */
793 static final class RandomIntsSpliterator implements Spliterator.OfInt {
794 long index;
795 final long fence;
796 final int origin;
797 final int bound;
798 RandomIntsSpliterator(long index, long fence,
799 int origin, int bound) {
800 this.index = index; this.fence = fence;
801 this.origin = origin; this.bound = bound;
802 }
803
804 public RandomIntsSpliterator trySplit() {
805 long i = index, m = (i + fence) >>> 1;
806 return (m <= i) ? null :
807 new RandomIntsSpliterator(i, index = m, origin, bound);
808 }
809
810 public long estimateSize() {
811 return fence - index;
812 }
813
814 public int characteristics() {
815 return (Spliterator.SIZED | Spliterator.SUBSIZED |
816 Spliterator.NONNULL | Spliterator.IMMUTABLE);
817 }
818
819 public boolean tryAdvance(IntConsumer consumer) {
820 if (consumer == null) throw new NullPointerException();
821 long i = index, f = fence;
822 if (i < f) {
823 consumer.accept(ThreadLocalRandom.current().internalNextInt(origin, bound));
824 index = i + 1;
825 return true;
826 }
827 return false;
828 }
829
830 public void forEachRemaining(IntConsumer consumer) {
831 if (consumer == null) throw new NullPointerException();
832 long i = index, f = fence;
833 if (i < f) {
834 index = f;
835 int o = origin, b = bound;
836 ThreadLocalRandom rng = ThreadLocalRandom.current();
837 do {
838 consumer.accept(rng.internalNextInt(o, b));
839 } while (++i < f);
840 }
841 }
842 }
843
844 /**
845 * Spliterator for long streams.
846 */
847 static final class RandomLongsSpliterator implements Spliterator.OfLong {
848 long index;
849 final long fence;
850 final long origin;
851 final long bound;
852 RandomLongsSpliterator(long index, long fence,
853 long origin, long bound) {
854 this.index = index; this.fence = fence;
855 this.origin = origin; this.bound = bound;
856 }
857
858 public RandomLongsSpliterator trySplit() {
859 long i = index, m = (i + fence) >>> 1;
860 return (m <= i) ? null :
861 new RandomLongsSpliterator(i, index = m, origin, bound);
862 }
863
864 public long estimateSize() {
865 return fence - index;
866 }
867
868 public int characteristics() {
869 return (Spliterator.SIZED | Spliterator.SUBSIZED |
870 Spliterator.NONNULL | Spliterator.IMMUTABLE);
871 }
872
873 public boolean tryAdvance(LongConsumer consumer) {
874 if (consumer == null) throw new NullPointerException();
875 long i = index, f = fence;
876 if (i < f) {
877 consumer.accept(ThreadLocalRandom.current().internalNextLong(origin, bound));
878 index = i + 1;
879 return true;
880 }
881 return false;
882 }
883
884 public void forEachRemaining(LongConsumer consumer) {
885 if (consumer == null) throw new NullPointerException();
886 long i = index, f = fence;
887 if (i < f) {
888 index = f;
889 long o = origin, b = bound;
890 ThreadLocalRandom rng = ThreadLocalRandom.current();
891 do {
892 consumer.accept(rng.internalNextLong(o, b));
893 } while (++i < f);
894 }
895 }
896
897 }
898
899 /**
900 * Spliterator for double streams.
901 */
902 static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
903 long index;
904 final long fence;
905 final double origin;
906 final double bound;
907 RandomDoublesSpliterator(long index, long fence,
908 double origin, double bound) {
909 this.index = index; this.fence = fence;
910 this.origin = origin; this.bound = bound;
911 }
912
913 public RandomDoublesSpliterator trySplit() {
914 long i = index, m = (i + fence) >>> 1;
915 return (m <= i) ? null :
916 new RandomDoublesSpliterator(i, index = m, origin, bound);
917 }
918
919 public long estimateSize() {
920 return fence - index;
921 }
922
923 public int characteristics() {
924 return (Spliterator.SIZED | Spliterator.SUBSIZED |
925 Spliterator.NONNULL | Spliterator.IMMUTABLE);
926 }
927
928 public boolean tryAdvance(DoubleConsumer consumer) {
929 if (consumer == null) throw new NullPointerException();
930 long i = index, f = fence;
931 if (i < f) {
932 consumer.accept(ThreadLocalRandom.current().internalNextDouble(origin, bound));
933 index = i + 1;
934 return true;
935 }
936 return false;
937 }
938
939 public void forEachRemaining(DoubleConsumer consumer) {
940 if (consumer == null) throw new NullPointerException();
941 long i = index, f = fence;
942 if (i < f) {
943 index = f;
944 double o = origin, b = bound;
945 ThreadLocalRandom rng = ThreadLocalRandom.current();
946 do {
947 consumer.accept(rng.internalNextDouble(o, b));
948 } while (++i < f);
949 }
950 }
951 }
952
953
954 // Within-package utilities
955
956 /*
957 * Descriptions of the usages of the methods below can be found in
958 * the classes that use them. Briefly, a thread's "probe" value is
959 * a non-zero hash code that (probably) does not collide with
960 * other existing threads with respect to any power of two
961 * collision space. When it does collide, it is pseudo-randomly
962 * adjusted (using a Marsaglia XorShift). The nextSecondarySeed
963 * method is used in the same contexts as ThreadLocalRandom, but
964 * only for transient usages such as random adaptive spin/block
965 * sequences for which a cheap RNG suffices and for which it could
966 * in principle disrupt user-visible statistical properties of the
967 * main ThreadLocalRandom if we were to use it.
968 *
969 * Note: Because of package-protection issues, versions of some
970 * these methods also appear in some subpackage classes.
971 */
972
973 /**
974 * Returns the probe value for the current thread without forcing
975 * initialization. Note that invoking ThreadLocalRandom.current()
976 * can be used to force initialization on zero return.
977 */
978 static final int getProbe() {
979 return UNSAFE.getInt(Thread.currentThread(), PROBE);
980 }
981
982 /**
983 * Pseudo-randomly advances and records the given probe value for the
984 * given thread.
985 */
986 static final int advanceProbe(int probe) {
987 probe ^= probe << 13; // xorshift
988 probe ^= probe >>> 17;
989 probe ^= probe << 5;
990 UNSAFE.putInt(Thread.currentThread(), PROBE, probe);
991 return probe;
992 }
993
994 /**
995 * Returns the pseudo-randomly initialized or updated secondary seed.
996 */
997 static final int nextSecondarySeed() {
998 int r;
999 Thread t = Thread.currentThread();
1000 if ((r = UNSAFE.getInt(t, SECONDARY)) != 0) {
1001 r ^= r << 13; // xorshift
1002 r ^= r >>> 17;
1003 r ^= r << 5;
1004 }
1005 else {
1006 localInit();
1007 if ((r = (int)UNSAFE.getLong(t, SEED)) == 0)
1008 r = 1; // avoid zero
1009 }
1010 UNSAFE.putInt(t, SECONDARY, r);
1011 return r;
1012 }
1013
1014 // Serialization support
1015
1016 private static final long serialVersionUID = -5851777807851030925L;
1017
1018 /**
1019 * @serialField rnd long
1020 * seed for random computations
1021 * @serialField initialized boolean
1022 * always true
1023 */
1024 private static final ObjectStreamField[] serialPersistentFields = {
1025 new ObjectStreamField("rnd", long.class),
1026 new ObjectStreamField("initialized", boolean.class),
1027 };
1028
1029 /**
1030 * Saves the {@code ThreadLocalRandom} to a stream (that is, serializes it).
1031 * @param s the stream
1032 * @throws java.io.IOException if an I/O error occurs
1033 */
1034 private void writeObject(java.io.ObjectOutputStream s)
1035 throws java.io.IOException {
1036
1037 java.io.ObjectOutputStream.PutField fields = s.putFields();
1038 fields.put("rnd", UNSAFE.getLong(Thread.currentThread(), SEED));
1039 fields.put("initialized", true);
1040 s.writeFields();
1041 }
1042
1043 /**
1044 * Returns the {@link #current() current} thread's {@code ThreadLocalRandom}.
1045 * @return the {@link #current() current} thread's {@code ThreadLocalRandom}
1046 */
1047 private Object readResolve() {
1048 return current();
1049 }
1050
1051 // Unsafe mechanics
1052 private static final sun.misc.Unsafe UNSAFE;
1053 private static final long SEED;
1054 private static final long PROBE;
1055 private static final long SECONDARY;
1056 static {
1057 try {
1058 UNSAFE = sun.misc.Unsafe.getUnsafe();
1059 Class<?> tk = Thread.class;
1060 SEED = UNSAFE.objectFieldOffset
1061 (tk.getDeclaredField("threadLocalRandomSeed"));
1062 PROBE = UNSAFE.objectFieldOffset
1063 (tk.getDeclaredField("threadLocalRandomProbe"));
1064 SECONDARY = UNSAFE.objectFieldOffset
1065 (tk.getDeclaredField("threadLocalRandomSecondarySeed"));
1066 } catch (Exception e) {
1067 throw new Error(e);
1068 }
1069 }
1070 }