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25 
26 package java.util;
27 
28 import java.util.concurrent.atomic.AtomicLong;
29 import java.util.function.IntConsumer;
30 import java.util.function.LongConsumer;
31 import java.util.function.DoubleConsumer;
32 import java.util.stream.StreamSupport;
33 import java.util.stream.IntStream;
34 import java.util.stream.LongStream;
35 import java.util.stream.DoubleStream;
36 
37 /**
38  * A generator of uniform pseudorandom values applicable for use in
39  * (among other contexts) isolated parallel computations that may
40  * generate subtasks. Class {@code SplittableRandom} supports methods for
41  * producing pseudorandom numbers of type {@code int}, {@code long},
42  * and {@code double} with similar usages as for class
43  * {@link java.util.Random} but differs in the following ways:
44  *
45  * <ul>
46  *
47  * <li>Series of generated values pass the DieHarder suite testing
48  * independence and uniformity properties of random number generators.
49  * (Most recently validated with <a
50  * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
51  * 3.31.1</a>.) These tests validate only the methods for certain
52  * types and ranges, but similar properties are expected to hold, at
53  * least approximately, for others as well. The <em>period</em>
54  * (length of any series of generated values before it repeats) is at
55  * least 2<sup>64</sup>. </li>
56  *
57  * <li> Method {@link #split} constructs and returns a new
58  * SplittableRandom instance that shares no mutable state with the
59  * current instance. However, with very high probability, the
60  * values collectively generated by the two objects have the same
61  * statistical properties as if the same quantity of values were
62  * generated by a single thread using a single {@code
63  * SplittableRandom} object.  </li>
64  *
65  * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
66  * They are designed to be split, not shared, across threads. For
67  * example, a {@link java.util.concurrent.ForkJoinTask
68  * fork/join-style} computation using random numbers might include a
69  * construction of the form {@code new
70  * Subtask(aSplittableRandom.split()).fork()}.
71  *
72  * <li>This class provides additional methods for generating random
73  * streams, that employ the above techniques when used in {@code
74  * stream.parallel()} mode.</li>
75  *
76  * </ul>
77  *
78  * <p>Instances of {@code SplittableRandom} are not cryptographically
79  * secure.  Consider instead using {@link java.security.SecureRandom}
80  * in security-sensitive applications. Additionally,
81  * default-constructed instances do not use a cryptographically random
82  * seed unless the {@linkplain System#getProperty system property}
83  * {@code java.util.secureRandomSeed} is set to {@code true}.
84  *
85  * @author  Guy Steele
86  * @author  Doug Lea
87  * @since   1.8
88  */
89 public final class SplittableRandom {
90 
91     /*
92      * Implementation Overview.
93      *
94      * This algorithm was inspired by the "DotMix" algorithm by
95      * Leiserson, Schardl, and Sukha "Deterministic Parallel
96      * Random-Number Generation for Dynamic-Multithreading Platforms",
97      * PPoPP 2012, as well as those in "Parallel random numbers: as
98      * easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011.  It
99      * differs mainly in simplifying and cheapening operations.
100      *
101      * The primary update step (method nextSeed()) is to add a
102      * constant ("gamma") to the current (64 bit) seed, forming a
103      * simple sequence.  The seed and the gamma values for any two
104      * SplittableRandom instances are highly likely to be different.
105      *
106      * Methods nextLong, nextInt, and derivatives do not return the
107      * sequence (seed) values, but instead a hash-like bit-mix of
108      * their bits, producing more independently distributed sequences.
109      * For nextLong, the mix64 function is based on David Stafford's
110      * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
111      * "Mix13" variant of the "64-bit finalizer" function in Austin
112      * Appleby's MurmurHash3 algorithm (see
113      * http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32
114      * function is based on Stafford's Mix04 mix function, but returns
115      * the upper 32 bits cast as int.
116      *
117      * The split operation uses the current generator to form the seed
118      * and gamma for another SplittableRandom.  To conservatively
119      * avoid potential correlations between seed and value generation,
120      * gamma selection (method mixGamma) uses different
121      * (Murmurhash3's) mix constants.  To avoid potential weaknesses
122      * in bit-mixing transformations, we restrict gammas to odd values
123      * with at least 24 0-1 or 1-0 bit transitions.  Rather than
124      * rejecting candidates with too few or too many bits set, method
125      * mixGamma flips some bits (which has the effect of mapping at
126      * most 4 to any given gamma value).  This reduces the effective
127      * set of 64bit odd gamma values by about 2%, and serves as an
128      * automated screening for sequence constant selection that is
129      * left as an empirical decision in some other hashing and crypto
130      * algorithms.
131      *
132      * The resulting generator thus transforms a sequence in which
133      * (typically) many bits change on each step, with an inexpensive
134      * mixer with good (but less than cryptographically secure)
135      * avalanching.
136      *
137      * The default (no-argument) constructor, in essence, invokes
138      * split() for a common "defaultGen" SplittableRandom.  Unlike
139      * other cases, this split must be performed in a thread-safe
140      * manner, so we use an AtomicLong to represent the seed rather
141      * than use an explicit SplittableRandom. To bootstrap the
142      * defaultGen, we start off using a seed based on current time
143      * unless the java.util.secureRandomSeed property is set. This
144      * serves as a slimmed-down (and insecure) variant of SecureRandom
145      * that also avoids stalls that may occur when using /dev/random.
146      *
147      * It is a relatively simple matter to apply the basic design here
148      * to use 128 bit seeds. However, emulating 128bit arithmetic and
149      * carrying around twice the state add more overhead than appears
150      * warranted for current usages.
151      *
152      * File organization: First the non-public methods that constitute
153      * the main algorithm, then the main public methods, followed by
154      * some custom spliterator classes needed for stream methods.
155      */
156 
157     /**
158      * The golden ratio scaled to 64bits, used as the initial gamma
159      * value for (unsplit) SplittableRandoms.
160      */
161     private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
162 
163     /**
164      * The least non-zero value returned by nextDouble(). This value
165      * is scaled by a random value of 53 bits to produce a result.
166      */
167     private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);
168 
169     /**
170      * The seed. Updated only via method nextSeed.
171      */
172     private long seed;
173 
174     /**
175      * The step value.
176      */
177     private final long gamma;
178 
179     /**
180      * Internal constructor used by all others except default constructor.
181      */
SplittableRandom(long seed, long gamma)182     private SplittableRandom(long seed, long gamma) {
183         this.seed = seed;
184         this.gamma = gamma;
185     }
186 
187     /**
188      * Computes Stafford variant 13 of 64bit mix function.
189      */
mix64(long z)190     private static long mix64(long z) {
191         z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
192         z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
193         return z ^ (z >>> 31);
194     }
195 
196     /**
197      * Returns the 32 high bits of Stafford variant 4 mix64 function as int.
198      */
mix32(long z)199     private static int mix32(long z) {
200         z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
201         return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
202     }
203 
204     /**
205      * Returns the gamma value to use for a new split instance.
206      */
mixGamma(long z)207     private static long mixGamma(long z) {
208         z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants
209         z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
210         z = (z ^ (z >>> 33)) | 1L;                  // force to be odd
211         int n = Long.bitCount(z ^ (z >>> 1));       // ensure enough transitions
212         return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
213     }
214 
215     /**
216      * Adds gamma to seed.
217      */
nextSeed()218     private long nextSeed() {
219         return seed += gamma;
220     }
221 
222     /**
223      * The seed generator for default constructors.
224      */
225     private static final AtomicLong defaultGen = new AtomicLong(initialSeed());
226 
initialSeed()227     private static long initialSeed() {
228         String pp = java.security.AccessController.doPrivileged(
229                 new sun.security.action.GetPropertyAction(
230                         "java.util.secureRandomSeed"));
231         if (pp != null && pp.equalsIgnoreCase("true")) {
232             byte[] seedBytes = java.security.SecureRandom.getSeed(8);
233             long s = (long)(seedBytes[0]) & 0xffL;
234             for (int i = 1; i < 8; ++i)
235                 s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
236             return s;
237         }
238         return (mix64(System.currentTimeMillis()) ^
239                 mix64(System.nanoTime()));
240     }
241 
242     // IllegalArgumentException messages
243     static final String BadBound = "bound must be positive";
244     static final String BadRange = "bound must be greater than origin";
245     static final String BadSize  = "size must be non-negative";
246 
247     /*
248      * Internal versions of nextX methods used by streams, as well as
249      * the public nextX(origin, bound) methods.  These exist mainly to
250      * avoid the need for multiple versions of stream spliterators
251      * across the different exported forms of streams.
252      */
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      */
internalNextLong(long origin, long bound)263     final long internalNextLong(long origin, long bound) {
264         /*
265          * Four Cases:
266          *
267          * 1. If the arguments indicate unbounded form, act as
268          * nextLong().
269          *
270          * 2. If the range is an exact power of two, apply the
271          * associated bit mask.
272          *
273          * 3. If the range is positive, loop to avoid potential bias
274          * when the implicit nextLong() bound (2<sup>64</sup>) is not
275          * evenly divisible by the range. The loop rejects candidates
276          * computed from otherwise over-represented values.  The
277          * expected number of iterations under an ideal generator
278          * varies from 1 to 2, depending on the bound. The loop itself
279          * takes an unlovable form. Because the first candidate is
280          * already available, we need a break-in-the-middle
281          * construction, which is concisely but cryptically performed
282          * within the while-condition of a body-less for loop.
283          *
284          * 4. Otherwise, the range cannot be represented as a positive
285          * long.  The loop repeatedly generates unbounded longs until
286          * obtaining a candidate meeting constraints (with an expected
287          * number of iterations of less than two).
288          */
289 
290         long r = mix64(nextSeed());
291         if (origin < bound) {
292             long n = bound - origin, m = n - 1;
293             if ((n & m) == 0L)  // power of two
294                 r = (r & m) + origin;
295             else if (n > 0L) {  // reject over-represented candidates
296                 for (long u = r >>> 1;            // ensure nonnegative
297                      u + m - (r = u % n) < 0L;    // rejection check
298                      u = mix64(nextSeed()) >>> 1) // retry
299                     ;
300                 r += origin;
301             }
302             else {              // range not representable as long
303                 while (r < origin || r >= bound)
304                     r = mix64(nextSeed());
305             }
306         }
307         return r;
308     }
309 
310     /**
311      * The form of nextInt used by IntStream Spliterators.
312      * Exactly the same as long version, except for types.
313      *
314      * @param origin the least value, unless greater than bound
315      * @param bound the upper bound (exclusive), must not equal origin
316      * @return a pseudorandom value
317      */
internalNextInt(int origin, int bound)318     final int internalNextInt(int origin, int bound) {
319         int r = mix32(nextSeed());
320         if (origin < bound) {
321             int n = bound - origin, m = n - 1;
322             if ((n & m) == 0)
323                 r = (r & m) + origin;
324             else if (n > 0) {
325                 for (int u = r >>> 1;
326                      u + m - (r = u % n) < 0;
327                      u = mix32(nextSeed()) >>> 1)
328                     ;
329                 r += origin;
330             }
331             else {
332                 while (r < origin || r >= bound)
333                     r = mix32(nextSeed());
334             }
335         }
336         return r;
337     }
338 
339     /**
340      * The form of nextDouble used by DoubleStream Spliterators.
341      *
342      * @param origin the least value, unless greater than bound
343      * @param bound the upper bound (exclusive), must not equal origin
344      * @return a pseudorandom value
345      */
internalNextDouble(double origin, double bound)346     final double internalNextDouble(double origin, double bound) {
347         double r = (nextLong() >>> 11) * DOUBLE_UNIT;
348         if (origin < bound) {
349             r = r * (bound - origin) + origin;
350             if (r >= bound) // correct for rounding
351                 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
352         }
353         return r;
354     }
355 
356     /* ---------------- public methods ---------------- */
357 
358     /**
359      * Creates a new SplittableRandom instance using the specified
360      * initial seed. SplittableRandom instances created with the same
361      * seed in the same program generate identical sequences of values.
362      *
363      * @param seed the initial seed
364      */
SplittableRandom(long seed)365     public SplittableRandom(long seed) {
366         this(seed, GOLDEN_GAMMA);
367     }
368 
369     /**
370      * Creates a new SplittableRandom instance that is likely to
371      * generate sequences of values that are statistically independent
372      * of those of any other instances in the current program; and
373      * may, and typically does, vary across program invocations.
374      */
SplittableRandom()375     public SplittableRandom() { // emulate defaultGen.split()
376         long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
377         this.seed = mix64(s);
378         this.gamma = mixGamma(s + GOLDEN_GAMMA);
379     }
380 
381     /**
382      * Constructs and returns a new SplittableRandom instance that
383      * shares no mutable state with this instance. However, with very
384      * high probability, the set of values collectively generated by
385      * the two objects has the same statistical properties as if the
386      * same quantity of values were generated by a single thread using
387      * a single SplittableRandom object.  Either or both of the two
388      * objects may be further split using the {@code split()} method,
389      * and the same expected statistical properties apply to the
390      * entire set of generators constructed by such recursive
391      * splitting.
392      *
393      * @return the new SplittableRandom instance
394      */
split()395     public SplittableRandom split() {
396         return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
397     }
398 
399     /**
400      * Returns a pseudorandom {@code int} value.
401      *
402      * @return a pseudorandom {@code int} value
403      */
nextInt()404     public int nextInt() {
405         return mix32(nextSeed());
406     }
407 
408     /**
409      * Returns a pseudorandom {@code int} value between zero (inclusive)
410      * and the specified bound (exclusive).
411      *
412      * @param bound the upper bound (exclusive).  Must be positive.
413      * @return a pseudorandom {@code int} value between zero
414      *         (inclusive) and the bound (exclusive)
415      * @throws IllegalArgumentException if {@code bound} is not positive
416      */
nextInt(int bound)417     public int nextInt(int bound) {
418         if (bound <= 0)
419             throw new IllegalArgumentException(BadBound);
420         // Specialize internalNextInt for origin 0
421         int r = mix32(nextSeed());
422         int m = bound - 1;
423         if ((bound & m) == 0) // power of two
424             r &= m;
425         else { // reject over-represented candidates
426             for (int u = r >>> 1;
427                  u + m - (r = u % bound) < 0;
428                  u = mix32(nextSeed()) >>> 1)
429                 ;
430         }
431         return r;
432     }
433 
434     /**
435      * Returns a pseudorandom {@code int} value between the specified
436      * origin (inclusive) and the specified bound (exclusive).
437      *
438      * @param origin the least value returned
439      * @param bound the upper bound (exclusive)
440      * @return a pseudorandom {@code int} value between the origin
441      *         (inclusive) and the bound (exclusive)
442      * @throws IllegalArgumentException if {@code origin} is greater than
443      *         or equal to {@code bound}
444      */
nextInt(int origin, int bound)445     public int nextInt(int origin, int bound) {
446         if (origin >= bound)
447             throw new IllegalArgumentException(BadRange);
448         return internalNextInt(origin, bound);
449     }
450 
451     /**
452      * Returns a pseudorandom {@code long} value.
453      *
454      * @return a pseudorandom {@code long} value
455      */
nextLong()456     public long nextLong() {
457         return mix64(nextSeed());
458     }
459 
460     /**
461      * Returns a pseudorandom {@code long} value between zero (inclusive)
462      * and the specified bound (exclusive).
463      *
464      * @param bound the upper bound (exclusive).  Must be positive.
465      * @return a pseudorandom {@code long} value between zero
466      *         (inclusive) and the bound (exclusive)
467      * @throws IllegalArgumentException if {@code bound} is not positive
468      */
nextLong(long bound)469     public long nextLong(long bound) {
470         if (bound <= 0)
471             throw new IllegalArgumentException(BadBound);
472         // Specialize internalNextLong for origin 0
473         long r = mix64(nextSeed());
474         long m = bound - 1;
475         if ((bound & m) == 0L) // power of two
476             r &= m;
477         else { // reject over-represented candidates
478             for (long u = r >>> 1;
479                  u + m - (r = u % bound) < 0L;
480                  u = mix64(nextSeed()) >>> 1)
481                 ;
482         }
483         return r;
484     }
485 
486     /**
487      * Returns a pseudorandom {@code long} value between the specified
488      * origin (inclusive) and the specified bound (exclusive).
489      *
490      * @param origin the least value returned
491      * @param bound the upper bound (exclusive)
492      * @return a pseudorandom {@code long} value between the origin
493      *         (inclusive) and the bound (exclusive)
494      * @throws IllegalArgumentException if {@code origin} is greater than
495      *         or equal to {@code bound}
496      */
nextLong(long origin, long bound)497     public long nextLong(long origin, long bound) {
498         if (origin >= bound)
499             throw new IllegalArgumentException(BadRange);
500         return internalNextLong(origin, bound);
501     }
502 
503     /**
504      * Returns a pseudorandom {@code double} value between zero
505      * (inclusive) and one (exclusive).
506      *
507      * @return a pseudorandom {@code double} value between zero
508      *         (inclusive) and one (exclusive)
509      */
nextDouble()510     public double nextDouble() {
511         return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
512     }
513 
514     /**
515      * Returns a pseudorandom {@code double} value between 0.0
516      * (inclusive) and the specified bound (exclusive).
517      *
518      * @param bound the upper bound (exclusive).  Must be positive.
519      * @return a pseudorandom {@code double} value between zero
520      *         (inclusive) and the bound (exclusive)
521      * @throws IllegalArgumentException if {@code bound} is not positive
522      */
nextDouble(double bound)523     public double nextDouble(double bound) {
524         if (!(bound > 0.0))
525             throw new IllegalArgumentException(BadBound);
526         double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
527         return (result < bound) ?  result : // correct for rounding
528             Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
529     }
530 
531     /**
532      * Returns a pseudorandom {@code double} value between the specified
533      * origin (inclusive) and bound (exclusive).
534      *
535      * @param origin the least value returned
536      * @param bound the upper bound (exclusive)
537      * @return a pseudorandom {@code double} value between the origin
538      *         (inclusive) and the bound (exclusive)
539      * @throws IllegalArgumentException if {@code origin} is greater than
540      *         or equal to {@code bound}
541      */
nextDouble(double origin, double bound)542     public double nextDouble(double origin, double bound) {
543         if (!(origin < bound))
544             throw new IllegalArgumentException(BadRange);
545         return internalNextDouble(origin, bound);
546     }
547 
548     /**
549      * Returns a pseudorandom {@code boolean} value.
550      *
551      * @return a pseudorandom {@code boolean} value
552      */
nextBoolean()553     public boolean nextBoolean() {
554         return mix32(nextSeed()) < 0;
555     }
556 
557     // stream methods, coded in a way intended to better isolate for
558     // maintenance purposes the small differences across forms.
559 
560     /**
561      * Returns a stream producing the given {@code streamSize} number
562      * of pseudorandom {@code int} values from this generator and/or
563      * one split from it.
564      *
565      * @param streamSize the number of values to generate
566      * @return a stream of pseudorandom {@code int} values
567      * @throws IllegalArgumentException if {@code streamSize} is
568      *         less than zero
569      */
ints(long streamSize)570     public IntStream ints(long streamSize) {
571         if (streamSize < 0L)
572             throw new IllegalArgumentException(BadSize);
573         return StreamSupport.intStream
574             (new RandomIntsSpliterator
575              (this, 0L, streamSize, Integer.MAX_VALUE, 0),
576              false);
577     }
578 
579     /**
580      * Returns an effectively unlimited stream of pseudorandom {@code int}
581      * values from this generator and/or one split from it.
582      *
583      * @implNote This method is implemented to be equivalent to {@code
584      * ints(Long.MAX_VALUE)}.
585      *
586      * @return a stream of pseudorandom {@code int} values
587      */
ints()588     public IntStream ints() {
589         return StreamSupport.intStream
590             (new RandomIntsSpliterator
591              (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
592              false);
593     }
594 
595     /**
596      * Returns a stream producing the given {@code streamSize} number
597      * of pseudorandom {@code int} values from this generator and/or one split
598      * from it; each value conforms to the given origin (inclusive) and bound
599      * (exclusive).
600      *
601      * @param streamSize the number of values to generate
602      * @param randomNumberOrigin the origin (inclusive) of each random value
603      * @param randomNumberBound the bound (exclusive) of each random value
604      * @return a stream of pseudorandom {@code int} values,
605      *         each with the given origin (inclusive) and bound (exclusive)
606      * @throws IllegalArgumentException if {@code streamSize} is
607      *         less than zero, or {@code randomNumberOrigin}
608      *         is greater than or equal to {@code randomNumberBound}
609      */
ints(long streamSize, int randomNumberOrigin, int randomNumberBound)610     public IntStream ints(long streamSize, int randomNumberOrigin,
611                           int randomNumberBound) {
612         if (streamSize < 0L)
613             throw new IllegalArgumentException(BadSize);
614         if (randomNumberOrigin >= randomNumberBound)
615             throw new IllegalArgumentException(BadRange);
616         return StreamSupport.intStream
617             (new RandomIntsSpliterator
618              (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
619              false);
620     }
621 
622     /**
623      * Returns an effectively unlimited stream of pseudorandom {@code
624      * int} values from this generator and/or one split from it; each value
625      * conforms to the given origin (inclusive) and bound (exclusive).
626      *
627      * @implNote This method is implemented to be equivalent to {@code
628      * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
629      *
630      * @param randomNumberOrigin the origin (inclusive) of each random value
631      * @param randomNumberBound the bound (exclusive) of each random value
632      * @return a stream of pseudorandom {@code int} values,
633      *         each with the given origin (inclusive) and bound (exclusive)
634      * @throws IllegalArgumentException if {@code randomNumberOrigin}
635      *         is greater than or equal to {@code randomNumberBound}
636      */
ints(int randomNumberOrigin, int randomNumberBound)637     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
638         if (randomNumberOrigin >= randomNumberBound)
639             throw new IllegalArgumentException(BadRange);
640         return StreamSupport.intStream
641             (new RandomIntsSpliterator
642              (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
643              false);
644     }
645 
646     /**
647      * Returns a stream producing the given {@code streamSize} number
648      * of pseudorandom {@code long} values from this generator and/or
649      * one split from it.
650      *
651      * @param streamSize the number of values to generate
652      * @return a stream of pseudorandom {@code long} values
653      * @throws IllegalArgumentException if {@code streamSize} is
654      *         less than zero
655      */
longs(long streamSize)656     public LongStream longs(long streamSize) {
657         if (streamSize < 0L)
658             throw new IllegalArgumentException(BadSize);
659         return StreamSupport.longStream
660             (new RandomLongsSpliterator
661              (this, 0L, streamSize, Long.MAX_VALUE, 0L),
662              false);
663     }
664 
665     /**
666      * Returns an effectively unlimited stream of pseudorandom {@code
667      * long} values from this generator and/or one split from it.
668      *
669      * @implNote This method is implemented to be equivalent to {@code
670      * longs(Long.MAX_VALUE)}.
671      *
672      * @return a stream of pseudorandom {@code long} values
673      */
longs()674     public LongStream longs() {
675         return StreamSupport.longStream
676             (new RandomLongsSpliterator
677              (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
678              false);
679     }
680 
681     /**
682      * Returns a stream producing the given {@code streamSize} number of
683      * pseudorandom {@code long} values from this generator and/or one split
684      * from it; each value conforms to the given origin (inclusive) and bound
685      * (exclusive).
686      *
687      * @param streamSize the number of values to generate
688      * @param randomNumberOrigin the origin (inclusive) of each random value
689      * @param randomNumberBound the bound (exclusive) of each random value
690      * @return a stream of pseudorandom {@code long} values,
691      *         each with the given origin (inclusive) and bound (exclusive)
692      * @throws IllegalArgumentException if {@code streamSize} is
693      *         less than zero, or {@code randomNumberOrigin}
694      *         is greater than or equal to {@code randomNumberBound}
695      */
longs(long streamSize, long randomNumberOrigin, long randomNumberBound)696     public LongStream longs(long streamSize, long randomNumberOrigin,
697                             long randomNumberBound) {
698         if (streamSize < 0L)
699             throw new IllegalArgumentException(BadSize);
700         if (randomNumberOrigin >= randomNumberBound)
701             throw new IllegalArgumentException(BadRange);
702         return StreamSupport.longStream
703             (new RandomLongsSpliterator
704              (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
705              false);
706     }
707 
708     /**
709      * Returns an effectively unlimited stream of pseudorandom {@code
710      * long} values from this generator and/or one split from it; each value
711      * conforms to the given origin (inclusive) and bound (exclusive).
712      *
713      * @implNote This method is implemented to be equivalent to {@code
714      * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
715      *
716      * @param randomNumberOrigin the origin (inclusive) of each random value
717      * @param randomNumberBound the bound (exclusive) of each random value
718      * @return a stream of pseudorandom {@code long} values,
719      *         each with the given origin (inclusive) and bound (exclusive)
720      * @throws IllegalArgumentException if {@code randomNumberOrigin}
721      *         is greater than or equal to {@code randomNumberBound}
722      */
longs(long randomNumberOrigin, long randomNumberBound)723     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
724         if (randomNumberOrigin >= randomNumberBound)
725             throw new IllegalArgumentException(BadRange);
726         return StreamSupport.longStream
727             (new RandomLongsSpliterator
728              (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
729              false);
730     }
731 
732     /**
733      * Returns a stream producing the given {@code streamSize} number of
734      * pseudorandom {@code double} values from this generator and/or one split
735      * from it; each value is between zero (inclusive) and one (exclusive).
736      *
737      * @param streamSize the number of values to generate
738      * @return a stream of {@code double} values
739      * @throws IllegalArgumentException if {@code streamSize} is
740      *         less than zero
741      */
doubles(long streamSize)742     public DoubleStream doubles(long streamSize) {
743         if (streamSize < 0L)
744             throw new IllegalArgumentException(BadSize);
745         return StreamSupport.doubleStream
746             (new RandomDoublesSpliterator
747              (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
748              false);
749     }
750 
751     /**
752      * Returns an effectively unlimited stream of pseudorandom {@code
753      * double} values from this generator and/or one split from it; each value
754      * is between zero (inclusive) and one (exclusive).
755      *
756      * @implNote This method is implemented to be equivalent to {@code
757      * doubles(Long.MAX_VALUE)}.
758      *
759      * @return a stream of pseudorandom {@code double} values
760      */
doubles()761     public DoubleStream doubles() {
762         return StreamSupport.doubleStream
763             (new RandomDoublesSpliterator
764              (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
765              false);
766     }
767 
768     /**
769      * Returns a stream producing the given {@code streamSize} number of
770      * pseudorandom {@code double} values from this generator and/or one split
771      * from it; each value conforms to the given origin (inclusive) and bound
772      * (exclusive).
773      *
774      * @param streamSize the number of values to generate
775      * @param randomNumberOrigin the origin (inclusive) of each random value
776      * @param randomNumberBound the bound (exclusive) of each random value
777      * @return a stream of pseudorandom {@code double} values,
778      *         each with the given origin (inclusive) and bound (exclusive)
779      * @throws IllegalArgumentException if {@code streamSize} is
780      *         less than zero
781      * @throws IllegalArgumentException if {@code randomNumberOrigin}
782      *         is greater than or equal to {@code randomNumberBound}
783      */
doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)784     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
785                                 double randomNumberBound) {
786         if (streamSize < 0L)
787             throw new IllegalArgumentException(BadSize);
788         if (!(randomNumberOrigin < randomNumberBound))
789             throw new IllegalArgumentException(BadRange);
790         return StreamSupport.doubleStream
791             (new RandomDoublesSpliterator
792              (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
793              false);
794     }
795 
796     /**
797      * Returns an effectively unlimited stream of pseudorandom {@code
798      * double} values from this generator and/or one split from it; each value
799      * conforms to the given origin (inclusive) and bound (exclusive).
800      *
801      * @implNote This method is implemented to be equivalent to {@code
802      * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
803      *
804      * @param randomNumberOrigin the origin (inclusive) of each random value
805      * @param randomNumberBound the bound (exclusive) of each random value
806      * @return a stream of pseudorandom {@code double} values,
807      *         each with the given origin (inclusive) and bound (exclusive)
808      * @throws IllegalArgumentException if {@code randomNumberOrigin}
809      *         is greater than or equal to {@code randomNumberBound}
810      */
doubles(double randomNumberOrigin, double randomNumberBound)811     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
812         if (!(randomNumberOrigin < randomNumberBound))
813             throw new IllegalArgumentException(BadRange);
814         return StreamSupport.doubleStream
815             (new RandomDoublesSpliterator
816              (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
817              false);
818     }
819 
820     /**
821      * Spliterator for int streams.  We multiplex the four int
822      * versions into one class by treating a bound less than origin as
823      * unbounded, and also by treating "infinite" as equivalent to
824      * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
825      * approach. The long and double versions of this class are
826      * identical except for types.
827      */
828     static final class RandomIntsSpliterator implements Spliterator.OfInt {
829         final SplittableRandom rng;
830         long index;
831         final long fence;
832         final int origin;
833         final int bound;
RandomIntsSpliterator(SplittableRandom rng, long index, long fence, int origin, int bound)834         RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
835                               int origin, int bound) {
836             this.rng = rng; this.index = index; this.fence = fence;
837             this.origin = origin; this.bound = bound;
838         }
839 
trySplit()840         public RandomIntsSpliterator trySplit() {
841             long i = index, m = (i + fence) >>> 1;
842             return (m <= i) ? null :
843                 new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
844         }
845 
estimateSize()846         public long estimateSize() {
847             return fence - index;
848         }
849 
characteristics()850         public int characteristics() {
851             return (Spliterator.SIZED | Spliterator.SUBSIZED |
852                     Spliterator.NONNULL | Spliterator.IMMUTABLE);
853         }
854 
tryAdvance(IntConsumer consumer)855         public boolean tryAdvance(IntConsumer consumer) {
856             if (consumer == null) throw new NullPointerException();
857             long i = index, f = fence;
858             if (i < f) {
859                 consumer.accept(rng.internalNextInt(origin, bound));
860                 index = i + 1;
861                 return true;
862             }
863             return false;
864         }
865 
forEachRemaining(IntConsumer consumer)866         public void forEachRemaining(IntConsumer consumer) {
867             if (consumer == null) throw new NullPointerException();
868             long i = index, f = fence;
869             if (i < f) {
870                 index = f;
871                 SplittableRandom r = rng;
872                 int o = origin, b = bound;
873                 do {
874                     consumer.accept(r.internalNextInt(o, b));
875                 } while (++i < f);
876             }
877         }
878     }
879 
880     /**
881      * Spliterator for long streams.
882      */
883     static final class RandomLongsSpliterator implements Spliterator.OfLong {
884         final SplittableRandom rng;
885         long index;
886         final long fence;
887         final long origin;
888         final long bound;
RandomLongsSpliterator(SplittableRandom rng, long index, long fence, long origin, long bound)889         RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
890                                long origin, long bound) {
891             this.rng = rng; this.index = index; this.fence = fence;
892             this.origin = origin; this.bound = bound;
893         }
894 
trySplit()895         public RandomLongsSpliterator trySplit() {
896             long i = index, m = (i + fence) >>> 1;
897             return (m <= i) ? null :
898                 new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
899         }
900 
estimateSize()901         public long estimateSize() {
902             return fence - index;
903         }
904 
characteristics()905         public int characteristics() {
906             return (Spliterator.SIZED | Spliterator.SUBSIZED |
907                     Spliterator.NONNULL | Spliterator.IMMUTABLE);
908         }
909 
tryAdvance(LongConsumer consumer)910         public boolean tryAdvance(LongConsumer consumer) {
911             if (consumer == null) throw new NullPointerException();
912             long i = index, f = fence;
913             if (i < f) {
914                 consumer.accept(rng.internalNextLong(origin, bound));
915                 index = i + 1;
916                 return true;
917             }
918             return false;
919         }
920 
forEachRemaining(LongConsumer consumer)921         public void forEachRemaining(LongConsumer consumer) {
922             if (consumer == null) throw new NullPointerException();
923             long i = index, f = fence;
924             if (i < f) {
925                 index = f;
926                 SplittableRandom r = rng;
927                 long o = origin, b = bound;
928                 do {
929                     consumer.accept(r.internalNextLong(o, b));
930                 } while (++i < f);
931             }
932         }
933 
934     }
935 
936     /**
937      * Spliterator for double streams.
938      */
939     static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
940         final SplittableRandom rng;
941         long index;
942         final long fence;
943         final double origin;
944         final double bound;
RandomDoublesSpliterator(SplittableRandom rng, long index, long fence, double origin, double bound)945         RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
946                                  double origin, double bound) {
947             this.rng = rng; this.index = index; this.fence = fence;
948             this.origin = origin; this.bound = bound;
949         }
950 
trySplit()951         public RandomDoublesSpliterator trySplit() {
952             long i = index, m = (i + fence) >>> 1;
953             return (m <= i) ? null :
954                 new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
955         }
956 
estimateSize()957         public long estimateSize() {
958             return fence - index;
959         }
960 
characteristics()961         public int characteristics() {
962             return (Spliterator.SIZED | Spliterator.SUBSIZED |
963                     Spliterator.NONNULL | Spliterator.IMMUTABLE);
964         }
965 
tryAdvance(DoubleConsumer consumer)966         public boolean tryAdvance(DoubleConsumer consumer) {
967             if (consumer == null) throw new NullPointerException();
968             long i = index, f = fence;
969             if (i < f) {
970                 consumer.accept(rng.internalNextDouble(origin, bound));
971                 index = i + 1;
972                 return true;
973             }
974             return false;
975         }
976 
forEachRemaining(DoubleConsumer consumer)977         public void forEachRemaining(DoubleConsumer consumer) {
978             if (consumer == null) throw new NullPointerException();
979             long i = index, f = fence;
980             if (i < f) {
981                 index = f;
982                 SplittableRandom r = rng;
983                 double o = origin, b = bound;
984                 do {
985                     consumer.accept(r.internalNextDouble(o, b));
986                 } while (++i < f);
987             }
988         }
989     }
990 
991 }
992