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Implement and Document useless next(int)

/* * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.util; import java.util.concurrent.atomic.AtomicLong; import java.util.function.DoubleConsumer; import java.util.function.IntConsumer; import java.util.function.LongConsumer; import java.util.stream.DoubleStream; import java.util.stream.IntStream; import java.util.stream.LongStream; import java.util.stream.StreamSupport; /** * A generator of uniform pseudorandom values applicable for use in * (among other contexts) isolated parallel computations that may * generate subtasks. Class {@code SplittableRandom} supports methods for * producing pseudorandom numbers of type {@code int}, {@code long}, * and {@code double} with similar usages as for class * {@link java.util.Random} but differs in the following ways: * * <ul> * * <li>Series of generated values pass the DieHarder suite testing * independence and uniformity properties of random number generators. * (Most recently validated with <a * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version * 3.31.1</a>.) These tests validate only the methods for certain * types and ranges, but similar properties are expected to hold, at * least approximately, for others as well. The <em>period</em> * (length of any series of generated values before it repeats) is at * least 2<sup>64</sup>. * * <li>Method {@link #split} constructs and returns a new * SplittableRandom instance that shares no mutable state with the * current instance. However, with very high probability, the * values collectively generated by the two objects have the same * statistical properties as if the same quantity of values were * generated by a single thread using a single {@code * SplittableRandom} object. * * <li>Instances of SplittableRandom are <em>not</em> thread-safe. * They are designed to be split, not shared, across threads. For * example, a {@link java.util.concurrent.ForkJoinTask * fork/join-style} computation using random numbers might include a * construction of the form {@code new * Subtask(aSplittableRandom.split()).fork()}. * * <li>This class provides additional methods for generating random * streams, that employ the above techniques when used in {@code * stream.parallel()} mode. * * </ul> * * <p>Instances of {@code SplittableRandom} are not cryptographically * secure. Consider instead using {@link java.security.SecureRandom} * in security-sensitive applications. Additionally, * default-constructed instances do not use a cryptographically random * seed unless the {@linkplain System#getProperty system property} * {@code java.util.secureRandomSeed} is set to {@code true}. * * @author Guy Steele * @author Doug Lea * @since 1.8 */ public final class SplittableRandom { /* * Implementation Overview. * * This algorithm was inspired by the "DotMix" algorithm by * Leiserson, Schardl, and Sukha "Deterministic Parallel * Random-Number Generation for Dynamic-Multithreading Platforms", * PPoPP 2012, as well as those in "Parallel random numbers: as * easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It * differs mainly in simplifying and cheapening operations. * * The primary update step (method nextSeed()) is to add a * constant ("gamma") to the current (64 bit) seed, forming a * simple sequence. The seed and the gamma values for any two * SplittableRandom instances are highly likely to be different. * * Methods nextLong, nextInt, and derivatives do not return the * sequence (seed) values, but instead a hash-like bit-mix of * their bits, producing more independently distributed sequences. * For nextLong, the mix64 function is based on David Stafford's * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html) * "Mix13" variant of the "64-bit finalizer" function in Austin * Appleby's MurmurHash3 algorithm (see * http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32 * function is based on Stafford's Mix04 mix function, but returns * the upper 32 bits cast as int. * * The split operation uses the current generator to form the seed * and gamma for another SplittableRandom. To conservatively * avoid potential correlations between seed and value generation, * gamma selection (method mixGamma) uses different * (Murmurhash3's) mix constants. To avoid potential weaknesses * in bit-mixing transformations, we restrict gammas to odd values * with at least 24 0-1 or 1-0 bit transitions. Rather than * rejecting candidates with too few or too many bits set, method * mixGamma flips some bits (which has the effect of mapping at * most 4 to any given gamma value). This reduces the effective * set of 64bit odd gamma values by about 2%, and serves as an * automated screening for sequence constant selection that is * left as an empirical decision in some other hashing and crypto * algorithms. * * The resulting generator thus transforms a sequence in which * (typically) many bits change on each step, with an inexpensive * mixer with good (but less than cryptographically secure) * avalanching. * * The default (no-argument) constructor, in essence, invokes * split() for a common "defaultGen" SplittableRandom. Unlike * other cases, this split must be performed in a thread-safe * manner, so we use an AtomicLong to represent the seed rather * than use an explicit SplittableRandom. To bootstrap the * defaultGen, we start off using a seed based on current time * unless the java.util.secureRandomSeed property is set. This * serves as a slimmed-down (and insecure) variant of SecureRandom * that also avoids stalls that may occur when using /dev/random. * * It is a relatively simple matter to apply the basic design here * to use 128 bit seeds. However, emulating 128bit arithmetic and * carrying around twice the state add more overhead than appears * warranted for current usages. * * File organization: First the non-public methods that constitute * the main algorithm, then the main public methods, followed by * some custom spliterator classes needed for stream methods. */ /** * The golden ratio scaled to 64bits, used as the initial gamma * value for (unsplit) SplittableRandoms. */ private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L; /** * The least non-zero value returned by nextDouble(). This value * is scaled by a random value of 53 bits to produce a result. */ private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53); /** * The seed. Updated only via method nextSeed. */ private long seed; /** * The step value. */ private final long gamma; /** * Internal constructor used by all others except default constructor. */ private SplittableRandom(long seed, long gamma) { this.seed = seed; this.gamma = gamma; } /** * Computes Stafford variant 13 of 64bit mix function. */ private static long mix64(long z) { z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; return z ^ (z >>> 31); } /** * Returns the 32 high bits of Stafford variant 4 mix64 function as int. */ private static int mix32(long z) { z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L; return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32); } /** * Returns the gamma value to use for a new split instance. */ private static long mixGamma(long z) { z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; z = (z ^ (z >>> 33)) | 1L; // force to be odd int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z; } /** * Adds gamma to seed. */ private long nextSeed() { return seed += gamma; } // IllegalArgumentException messages static final String BAD_BOUND = "bound must be positive"; static final String BAD_RANGE = "bound must be greater than origin"; static final String BAD_SIZE = "size must be non-negative"; /** * The seed generator for default constructors. */ private static final AtomicLong defaultGen = new AtomicLong(mix64(System.currentTimeMillis()) ^ mix64(System.nanoTime())); // at end of <clinit> to survive static initialization circularity static { if (java.security.AccessController.doPrivileged( new java.security.PrivilegedAction<Boolean>() { public Boolean run() { return Boolean.getBoolean("java.util.secureRandomSeed"); }})) { byte[] seedBytes = java.security.SecureRandom.getSeed(8); long s = (long)seedBytes[0] & 0xffL; for (int i = 1; i < 8; ++i) s = (s << 8) | ((long)seedBytes[i] & 0xffL); defaultGen.set(s); } } /* * Internal versions of nextX methods used by streams, as well as * the public nextX(origin, bound) methods. These exist mainly to * avoid the need for multiple versions of stream spliterators * across the different exported forms of streams. */ /** * The form of nextLong used by LongStream Spliterators. If * origin is greater than bound, acts as unbounded form of * nextLong, else as bounded form. * * @param origin the least value, unless greater than bound * @param bound the upper bound (exclusive), must not equal origin * @return a pseudorandom value */ final long internalNextLong(long origin, long bound) { /* * Four Cases: * * 1. If the arguments indicate unbounded form, act as * nextLong(). * * 2. If the range is an exact power of two, apply the * associated bit mask. * * 3. If the range is positive, loop to avoid potential bias * when the implicit nextLong() bound (2<sup>64</sup>) is not * evenly divisible by the range. The loop rejects candidates * computed from otherwise over-represented values. The * expected number of iterations under an ideal generator * varies from 1 to 2, depending on the bound. The loop itself * takes an unlovable form. Because the first candidate is * already available, we need a break-in-the-middle * construction, which is concisely but cryptically performed * within the while-condition of a body-less for loop. * * 4. Otherwise, the range cannot be represented as a positive * long. The loop repeatedly generates unbounded longs until * obtaining a candidate meeting constraints (with an expected * number of iterations of less than two). */ long r = mix64(nextSeed()); if (origin < bound) { long n = bound - origin, m = n - 1; if ((n & m) == 0L) // power of two r = (r & m) + origin; else if (n > 0L) { // reject over-represented candidates for (long u = r >>> 1; // ensure nonnegative u + m - (r = u % n) < 0L; // rejection check u = mix64(nextSeed()) >>> 1) // retry ; r += origin; } else { // range not representable as long while (r < origin || r >= bound) r = mix64(nextSeed()); } } return r; } /** * The form of nextInt used by IntStream Spliterators. * Exactly the same as long version, except for types. * * @param origin the least value, unless greater than bound * @param bound the upper bound (exclusive), must not equal origin * @return a pseudorandom value */ final int internalNextInt(int origin, int bound) { int r = mix32(nextSeed()); if (origin < bound) { int n = bound - origin, m = n - 1; if ((n & m) == 0) r = (r & m) + origin; else if (n > 0) { for (int u = r >>> 1; u + m - (r = u % n) < 0; u = mix32(nextSeed()) >>> 1) ; r += origin; } else { while (r < origin || r >= bound) r = mix32(nextSeed()); } } return r; } /** * The form of nextDouble used by DoubleStream Spliterators. * * @param origin the least value, unless greater than bound * @param bound the upper bound (exclusive), must not equal origin * @return a pseudorandom value */ final double internalNextDouble(double origin, double bound) { double r = (nextLong() >>> 11) * DOUBLE_UNIT; if (origin < bound) { r = r * (bound - origin) + origin; if (r >= bound) // correct for rounding r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); } return r; } /* ---------------- public methods ---------------- */ /** * Creates a new SplittableRandom instance using the specified * initial seed. SplittableRandom instances created with the same * seed in the same program generate identical sequences of values. * * @param seed the initial seed */ public SplittableRandom(long seed) { this(seed, GOLDEN_GAMMA); } /** * Creates a new SplittableRandom instance that is likely to * generate sequences of values that are statistically independent * of those of any other instances in the current program; and * may, and typically does, vary across program invocations. */ public SplittableRandom() { // emulate defaultGen.split() long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA); this.seed = mix64(s); this.gamma = mixGamma(s + GOLDEN_GAMMA); } /** * Constructs and returns a new SplittableRandom instance that * shares no mutable state with this instance. However, with very * high probability, the set of values collectively generated by * the two objects has the same statistical properties as if the * same quantity of values were generated by a single thread using * a single SplittableRandom object. Either or both of the two * objects may be further split using the {@code split()} method, * and the same expected statistical properties apply to the * entire set of generators constructed by such recursive * splitting. * * @return the new SplittableRandom instance */ public SplittableRandom split() { return new SplittableRandom(nextLong(), mixGamma(nextSeed())); } /** * Returns a pseudorandom {@code int} value. * * @return a pseudorandom {@code int} value */ public int nextInt() { return mix32(nextSeed()); } /** * Returns a pseudorandom {@code int} value between zero (inclusive) * and the specified bound (exclusive). * * @param bound the upper bound (exclusive). Must be positive. * @return a pseudorandom {@code int} value between zero * (inclusive) and the bound (exclusive) * @throws IllegalArgumentException if {@code bound} is not positive */ public int nextInt(int bound) { if (bound <= 0) throw new IllegalArgumentException(BAD_BOUND); // Specialize internalNextInt for origin 0 int r = mix32(nextSeed()); int m = bound - 1; if ((bound & m) == 0) // power of two r &= m; else { // reject over-represented candidates for (int u = r >>> 1; u + m - (r = u % bound) < 0; u = mix32(nextSeed()) >>> 1) ; } return r; } /** * Returns a pseudorandom {@code int} value between the specified * origin (inclusive) and the specified bound (exclusive). * * @param origin the least value returned * @param bound the upper bound (exclusive) * @return a pseudorandom {@code int} value between the origin * (inclusive) and the bound (exclusive) * @throws IllegalArgumentException if {@code origin} is greater than * or equal to {@code bound} */ public int nextInt(int origin, int bound) { if (origin >= bound) throw new IllegalArgumentException(BAD_RANGE); return internalNextInt(origin, bound); } /** * Returns a pseudorandom {@code long} value. * * @return a pseudorandom {@code long} value */ public long nextLong() { return mix64(nextSeed()); } /** * Returns a pseudorandom {@code long} value between zero (inclusive) * and the specified bound (exclusive). * * @param bound the upper bound (exclusive). Must be positive. * @return a pseudorandom {@code long} value between zero * (inclusive) and the bound (exclusive) * @throws IllegalArgumentException if {@code bound} is not positive */ public long nextLong(long bound) { if (bound <= 0) throw new IllegalArgumentException(BAD_BOUND); // Specialize internalNextLong for origin 0 long r = mix64(nextSeed()); long m = bound - 1; if ((bound & m) == 0L) // power of two r &= m; else { // reject over-represented candidates for (long u = r >>> 1; u + m - (r = u % bound) < 0L; u = mix64(nextSeed()) >>> 1) ; } return r; } /** * Returns a pseudorandom {@code long} value between the specified * origin (inclusive) and the specified bound (exclusive). * * @param origin the least value returned * @param bound the upper bound (exclusive) * @return a pseudorandom {@code long} value between the origin * (inclusive) and the bound (exclusive) * @throws IllegalArgumentException if {@code origin} is greater than * or equal to {@code bound} */ public long nextLong(long origin, long bound) { if (origin >= bound) throw new IllegalArgumentException(BAD_RANGE); return internalNextLong(origin, bound); } /** * Returns a pseudorandom {@code double} value between zero * (inclusive) and one (exclusive). * * @return a pseudorandom {@code double} value between zero * (inclusive) and one (exclusive) */ public double nextDouble() { return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; } /** * Returns a pseudorandom {@code double} value between 0.0 * (inclusive) and the specified bound (exclusive). * * @param bound the upper bound (exclusive). Must be positive. * @return a pseudorandom {@code double} value between zero * (inclusive) and the bound (exclusive) * @throws IllegalArgumentException if {@code bound} is not positive */ public double nextDouble(double bound) { if (!(bound > 0.0)) throw new IllegalArgumentException(BAD_BOUND); double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; return (result < bound) ? result : // correct for rounding Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); } /** * Generates a pseudorandom number with the indicated number of * bits. Unlike in superclass @{link Random}, this method is never * internally called or used by any other publicly accessible * method. * * @param bits random bits * @return the next pseudorandom value from this random number * generator's sequence */ protected int next(int bits) { return (int)(nextLong() >>> (64 - bits)); } /** * Returns a pseudorandom {@code double} value between the specified * origin (inclusive) and bound (exclusive). * * @param origin the least value returned * @param bound the upper bound (exclusive) * @return a pseudorandom {@code double} value between the origin * (inclusive) and the bound (exclusive) * @throws IllegalArgumentException if {@code origin} is greater than * or equal to {@code bound} */ public double nextDouble(double origin, double bound) { if (!(origin < bound)) throw new IllegalArgumentException(BAD_RANGE); return internalNextDouble(origin, bound); } /** * Returns a pseudorandom {@code boolean} value. * * @return a pseudorandom {@code boolean} value */ public boolean nextBoolean() { return mix32(nextSeed()) < 0; } // stream methods, coded in a way intended to better isolate for // maintenance purposes the small differences across forms. /** * Returns a stream producing the given {@code streamSize} number * of pseudorandom {@code int} values from this generator and/or * one split from it. * * @param streamSize the number of values to generate * @return a stream of pseudorandom {@code int} values * @throws IllegalArgumentException if {@code streamSize} is * less than zero */ public IntStream ints(long streamSize) { if (streamSize < 0L) throw new IllegalArgumentException(BAD_SIZE); return StreamSupport.intStream (new RandomIntsSpliterator (this, 0L, streamSize, Integer.MAX_VALUE, 0), false); } /** * Returns an effectively unlimited stream of pseudorandom {@code int} * values from this generator and/or one split from it. * * @implNote This method is implemented to be equivalent to {@code * ints(Long.MAX_VALUE)}. * * @return a stream of pseudorandom {@code int} values */ public IntStream ints() { return StreamSupport.intStream (new RandomIntsSpliterator (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), false); } /** * Returns a stream producing the given {@code streamSize} number * of pseudorandom {@code int} values from this generator and/or one split * from it; each value conforms to the given origin (inclusive) and bound * (exclusive). * * @param streamSize the number of values to generate * @param randomNumberOrigin the origin (inclusive) of each random value * @param randomNumberBound the bound (exclusive) of each random value * @return a stream of pseudorandom {@code int} values, * each with the given origin (inclusive) and bound (exclusive) * @throws IllegalArgumentException if {@code streamSize} is * less than zero, or {@code randomNumberOrigin} * is greater than or equal to {@code randomNumberBound} */ public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound) { if (streamSize < 0L) throw new IllegalArgumentException(BAD_SIZE); if (randomNumberOrigin >= randomNumberBound) throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.intStream (new RandomIntsSpliterator (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), false); } /** * Returns an effectively unlimited stream of pseudorandom {@code * int} values from this generator and/or one split from it; each value * conforms to the given origin (inclusive) and bound (exclusive). * * @implNote This method is implemented to be equivalent to {@code * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. * * @param randomNumberOrigin the origin (inclusive) of each random value * @param randomNumberBound the bound (exclusive) of each random value * @return a stream of pseudorandom {@code int} values, * each with the given origin (inclusive) and bound (exclusive) * @throws IllegalArgumentException if {@code randomNumberOrigin} * is greater than or equal to {@code randomNumberBound} */ public IntStream ints(int randomNumberOrigin, int randomNumberBound) { if (randomNumberOrigin >= randomNumberBound) throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.intStream (new RandomIntsSpliterator (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), false); } /** * Returns a stream producing the given {@code streamSize} number * of pseudorandom {@code long} values from this generator and/or * one split from it. * * @param streamSize the number of values to generate * @return a stream of pseudorandom {@code long} values * @throws IllegalArgumentException if {@code streamSize} is * less than zero */ public LongStream longs(long streamSize) { if (streamSize < 0L) throw new IllegalArgumentException(BAD_SIZE); return StreamSupport.longStream (new RandomLongsSpliterator (this, 0L, streamSize, Long.MAX_VALUE, 0L), false); } /** * Returns an effectively unlimited stream of pseudorandom {@code * long} values from this generator and/or one split from it. * * @implNote This method is implemented to be equivalent to {@code * longs(Long.MAX_VALUE)}. * * @return a stream of pseudorandom {@code long} values */ public LongStream longs() { return StreamSupport.longStream (new RandomLongsSpliterator (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), false); } /** * Returns a stream producing the given {@code streamSize} number of * pseudorandom {@code long} values from this generator and/or one split * from it; each value conforms to the given origin (inclusive) and bound * (exclusive). * * @param streamSize the number of values to generate * @param randomNumberOrigin the origin (inclusive) of each random value * @param randomNumberBound the bound (exclusive) of each random value * @return a stream of pseudorandom {@code long} values, * each with the given origin (inclusive) and bound (exclusive) * @throws IllegalArgumentException if {@code streamSize} is * less than zero, or {@code randomNumberOrigin} * is greater than or equal to {@code randomNumberBound} */ public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound) { if (streamSize < 0L) throw new IllegalArgumentException(BAD_SIZE); if (randomNumberOrigin >= randomNumberBound) throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.longStream (new RandomLongsSpliterator (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), false); } /** * Returns an effectively unlimited stream of pseudorandom {@code * long} values from this generator and/or one split from it; each value * conforms to the given origin (inclusive) and bound (exclusive). * * @implNote This method is implemented to be equivalent to {@code * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. * * @param randomNumberOrigin the origin (inclusive) of each random value * @param randomNumberBound the bound (exclusive) of each random value * @return a stream of pseudorandom {@code long} values, * each with the given origin (inclusive) and bound (exclusive) * @throws IllegalArgumentException if {@code randomNumberOrigin} * is greater than or equal to {@code randomNumberBound} */ public LongStream longs(long randomNumberOrigin, long randomNumberBound) { if (randomNumberOrigin >= randomNumberBound) throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.longStream (new RandomLongsSpliterator (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), false); } /** * Returns a stream producing the given {@code streamSize} number of * pseudorandom {@code double} values from this generator and/or one split * from it; each value is between zero (inclusive) and one (exclusive). * * @param streamSize the number of values to generate * @return a stream of {@code double} values * @throws IllegalArgumentException if {@code streamSize} is * less than zero */ public DoubleStream doubles(long streamSize) { if (streamSize < 0L) throw new IllegalArgumentException(BAD_SIZE); return StreamSupport.doubleStream (new RandomDoublesSpliterator (this, 0L, streamSize, Double.MAX_VALUE, 0.0), false); } /** * Returns an effectively unlimited stream of pseudorandom {@code * double} values from this generator and/or one split from it; each value * is between zero (inclusive) and one (exclusive). * * @implNote This method is implemented to be equivalent to {@code * doubles(Long.MAX_VALUE)}. * * @return a stream of pseudorandom {@code double} values */ public DoubleStream doubles() { return StreamSupport.doubleStream (new RandomDoublesSpliterator (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), false); } /** * Returns a stream producing the given {@code streamSize} number of * pseudorandom {@code double} values from this generator and/or one split * from it; each value conforms to the given origin (inclusive) and bound * (exclusive). * * @param streamSize the number of values to generate * @param randomNumberOrigin the origin (inclusive) of each random value * @param randomNumberBound the bound (exclusive) of each random value * @return a stream of pseudorandom {@code double} values, * each with the given origin (inclusive) and bound (exclusive) * @throws IllegalArgumentException if {@code streamSize} is * less than zero * @throws IllegalArgumentException if {@code randomNumberOrigin} * is greater than or equal to {@code randomNumberBound} */ public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound) { if (streamSize < 0L) throw new IllegalArgumentException(BAD_SIZE); if (!(randomNumberOrigin < randomNumberBound)) throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.doubleStream (new RandomDoublesSpliterator (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), false); } /** * Returns an effectively unlimited stream of pseudorandom {@code * double} values from this generator and/or one split from it; each value * conforms to the given origin (inclusive) and bound (exclusive). * * @implNote This method is implemented to be equivalent to {@code * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. * * @param randomNumberOrigin the origin (inclusive) of each random value * @param randomNumberBound the bound (exclusive) of each random value * @return a stream of pseudorandom {@code double} values, * each with the given origin (inclusive) and bound (exclusive) * @throws IllegalArgumentException if {@code randomNumberOrigin} * is greater than or equal to {@code randomNumberBound} */ public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { if (!(randomNumberOrigin < randomNumberBound)) throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.doubleStream (new RandomDoublesSpliterator (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), false); } /** * Spliterator for int streams. We multiplex the four int * versions into one class by treating a bound less than origin as * unbounded, and also by treating "infinite" as equivalent to * Long.MAX_VALUE. For splits, it uses the standard divide-by-two * approach. The long and double versions of this class are * identical except for types. */ private static final class RandomIntsSpliterator implements Spliterator.OfInt { final SplittableRandom rng; long index; final long fence; final int origin; final int bound; RandomIntsSpliterator(SplittableRandom rng, long index, long fence, int origin, int bound) { this.rng = rng; this.index = index; this.fence = fence; this.origin = origin; this.bound = bound; } public RandomIntsSpliterator trySplit() { long i = index, m = (i + fence) >>> 1; return (m <= i) ? null : new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound); } public long estimateSize() { return fence - index; } public int characteristics() { return (Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL | Spliterator.IMMUTABLE); } public boolean tryAdvance(IntConsumer consumer) { if (consumer == null) throw new NullPointerException(); long i = index, f = fence; if (i < f) { consumer.accept(rng.internalNextInt(origin, bound)); index = i + 1; return true; } return false; } public void forEachRemaining(IntConsumer consumer) { if (consumer == null) throw new NullPointerException(); long i = index, f = fence; if (i < f) { index = f; SplittableRandom r = rng; int o = origin, b = bound; do { consumer.accept(r.internalNextInt(o, b)); } while (++i < f); } } } /** * Spliterator for long streams. */ private static final class RandomLongsSpliterator implements Spliterator.OfLong { final SplittableRandom rng; long index; final long fence; final long origin; final long bound; RandomLongsSpliterator(SplittableRandom rng, long index, long fence, long origin, long bound) { this.rng = rng; this.index = index; this.fence = fence; this.origin = origin; this.bound = bound; } public RandomLongsSpliterator trySplit() { long i = index, m = (i + fence) >>> 1; return (m <= i) ? null : new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound); } public long estimateSize() { return fence - index; } public int characteristics() { return (Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL | Spliterator.IMMUTABLE); } public boolean tryAdvance(LongConsumer consumer) { if (consumer == null) throw new NullPointerException(); long i = index, f = fence; if (i < f) { consumer.accept(rng.internalNextLong(origin, bound)); index = i + 1; return true; } return false; } public void forEachRemaining(LongConsumer consumer) { if (consumer == null) throw new NullPointerException(); long i = index, f = fence; if (i < f) { index = f; SplittableRandom r = rng; long o = origin, b = bound; do { consumer.accept(r.internalNextLong(o, b)); } while (++i < f); } } } /** * Spliterator for double streams. */ private static final class RandomDoublesSpliterator implements Spliterator.OfDouble { final SplittableRandom rng; long index; final long fence; final double origin; final double bound; RandomDoublesSpliterator(SplittableRandom rng, long index, long fence, double origin, double bound) { this.rng = rng; this.index = index; this.fence = fence; this.origin = origin; this.bound = bound; } public RandomDoublesSpliterator trySplit() { long i = index, m = (i + fence) >>> 1; return (m <= i) ? null : new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound); } public long estimateSize() { return fence - index; } public int characteristics() { return (Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL | Spliterator.IMMUTABLE); } public boolean tryAdvance(DoubleConsumer consumer) { if (consumer == null) throw new NullPointerException(); long i = index, f = fence; if (i < f) { consumer.accept(rng.internalNextDouble(origin, bound)); index = i + 1; return true; } return false; } public void forEachRemaining(DoubleConsumer consumer) { if (consumer == null) throw new NullPointerException(); long i = index, f = fence; if (i < f) { index = f; SplittableRandom r = rng; double o = origin, b = bound; do { consumer.accept(r.internalNextDouble(o, b)); } while (++i < f); } } } }

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