8020292: j.u.SplittableRandom

Reviewed-by: mduigou
Contributed-by: NGuy Steele &lt;guy.steele@oracle.com&gt;, Doug Lea &lt;dl@cs.oswego.edu&gt;, Brian Goetz &lt;brian.goetz@oracle.com&gt;, Paul Sandoz <paul.sandoz@oracle.com>

src/share/classes/java/util/SplittableRandom.java

+/*
+ * 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.security.SecureRandom;
+import java.net.InetAddress;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.IntConsumer;
+import java.util.function.LongConsumer;
+import java.util.function.DoubleConsumer;
+import java.util.stream.StreamSupport;
+import java.util.stream.IntStream;
+import java.util.stream.LongStream;
+import java.util.stream.DoubleStream;
+
+/**
+ * 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>
+ *
+ * <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>
+ *
+ * <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.</li>
+ *
+ * </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 bit-mixing function computes the same
+     * value as the "64-bit finalizer" function in Austin Appleby's
+     * MurmurHash3 algorithm.  See
+     * http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
+     * comments: "The constants for the finalizers were generated by a
+     * simple simulated-annealing algorithm, and both avalanche all
+     * bits of 'h' to within 0.25% bias." The mix32 function is
+     * equivalent to (int)(mix64(seed) >>> 32), but faster because it
+     * omits a step that doesn't contribute to result.
+     *
+     * 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 nextGamma) uses the "Mix13" constants
+     * for MurmurHash3 described by David Stafford
+     * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
+     * To avoid potential weaknesses in bit-mixing transformations, we
+     * restrict gammas to odd values with at least 12 and no more than
+     * 52 bits set.  Rather than rejecting candidates with too few or
+     * too many bits set, method nextGamma 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<sup>14</sup>, a very tiny percentage, 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 "seeder" 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 seeder, we start
+     * off using a seed based on current time and host 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 initial gamma value for (unsplit) SplittableRandoms. Must
+     * be odd with at least 12 and no more than 52 bits set. Currently
+     * set to the golden ratio scaled to 64bits.
+     */
+    private static final long INITIAL_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 = 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 MurmurHash3 64bit mix function.
+     */
+    private static long mix64(long z) {
+        z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
+        z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
+        return z ^ (z >>> 33);
+    }
+
+    /**
+     * Returns the 32 high bits of mix64(z) as int.
+     */
+    private static int mix32(long z) {
+        z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
+        return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
+    }
+
+    /**
+     * Returns the gamma value to use for a new split instance.
+     */
+    private static long nextGamma(long z) {
+        z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; // Stafford "Mix13"
+        z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
+        z = (z ^ (z >>> 31)) | 1L; // force to be odd
+        int n = Long.bitCount(z);  // ensure enough 0 and 1 bits
+        return (n < 12 || n > 52) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
+    }
+
+    /**
+     * Adds gamma to seed.
+     */
+    private long nextSeed() {
+        return seed += gamma;
+    }
+
+    /**
+     * The seed generator for default constructors.
+     */
+    private static final AtomicLong seeder = new AtomicLong(initialSeed());
+
+    private static long initialSeed() {
+        String pp = java.security.AccessController.doPrivileged(
+                new sun.security.action.GetPropertyAction(
+                        "java.util.secureRandomSeed"));
+        if (pp != null && pp.equalsIgnoreCase("true")) {
+            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);
+            return s;
+        }
+        int hh = 0; // hashed host address
+        try {
+            hh = InetAddress.getLocalHost().hashCode();
+        } catch (Exception ignore) {
+        }
+        return (mix64((((long)hh) << 32) ^ System.currentTimeMillis()) ^
+                mix64(System.nanoTime()));
+    }
+
+    // IllegalArgumentException messages
+    static final String BadBound = "bound must be positive";
+    static final String BadRange = "bound must be greater than origin";
+    static final String BadSize  = "size must be non-negative";
+
+    /*
+     * 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, INITIAL_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 seeder.split()
+        this.gamma = nextGamma(this.seed = seeder.addAndGet(INITIAL_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() {
+        long s = nextSeed();
+        return new SplittableRandom(s, nextGamma(s));
+    }
+
+    /**
+     * 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(BadBound);
+        // 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(BadRange);
+        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(BadBound);
+        // 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(BadRange);
+        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(BadBound);
+        double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
+        return (result < bound) ?  result : // correct for rounding
+            Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
+    }
+
+    /**
+     * 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(BadRange);
+        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(BadSize);
+        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(BadSize);
+        if (randomNumberOrigin >= randomNumberBound)
+            throw new IllegalArgumentException(BadRange);
+        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(BadRange);
+        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(BadSize);
+        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(BadSize);
+        if (randomNumberOrigin >= randomNumberBound)
+            throw new IllegalArgumentException(BadRange);
+        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(BadRange);
+        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(BadSize);
+        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(BadSize);
+        if (!(randomNumberOrigin < randomNumberBound))
+            throw new IllegalArgumentException(BadRange);
+        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(BadRange);
+        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.
+     */
+    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.
+     */
+    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.
+     */
+    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);
+            }
+        }
+    }
+
+}

test/java/util/SplittableRandom/SplittableRandomTest.java

+/*
+ * Copyright (c) 2012, 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.
+ *
+ * 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.
+ */
+
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import java.util.SplittableRandom;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.LongAdder;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertNotNull;
+import static org.testng.AssertJUnit.assertTrue;
+
+/**
+ * @test
+ * @run testng SplittableRandomTest
+ * @run testng/othervm -Djava.util.secureRandomSeed=true SplittableRandomTest
+ * @summary test methods on SplittableRandom
+ */
+@Test
+public class SplittableRandomTest {
+
+    // Note: this test was copied from the 166 TCK SplittableRandomTest test
+    // and modified to be a TestNG test
+
+    /*
+     * Testing coverage notes:
+     *
+     * 1. Many of the test methods are adapted from ThreadLocalRandomTest.
+     *
+     * 2. These tests do not check for random number generator quality.
+     * But we check for minimal API compliance by requiring that
+     * repeated calls to nextX methods, up to NCALLS tries, produce at
+     * least two distinct results. (In some possible universe, a
+     * "correct" implementation might fail, but the odds are vastly
+     * less than that of encountering a hardware failure while running
+     * the test.) For bounded nextX methods, we sample various
+     * intervals across multiples of primes. In other tests, we repeat
+     * under REPS different values.
+     */
+
+    // max numbers of calls to detect getting stuck on one value
+    static final int NCALLS = 10000;
+
+    // max sampled int bound
+    static final int MAX_INT_BOUND = (1 << 28);
+
+    // max sampled long bound
+    static final long MAX_LONG_BOUND = (1L << 42);
+
+    // Number of replications for other checks
+    static final int REPS = 20;
+
+    /**
+     * Repeated calls to nextInt produce at least two distinct results
+     */
+    public void testNextInt() {
+        SplittableRandom sr = new SplittableRandom();
+        int f = sr.nextInt();
+        int i = 0;
+        while (i < NCALLS && sr.nextInt() == f)
+            ++i;
+        assertTrue(i < NCALLS);
+    }
+
+    /**
+     * Repeated calls to nextLong produce at least two distinct results
+     */
+    public void testNextLong() {
+        SplittableRandom sr = new SplittableRandom();
+        long f = sr.nextLong();
+        int i = 0;
+        while (i < NCALLS && sr.nextLong() == f)
+            ++i;
+        assertTrue(i < NCALLS);
+    }
+
+    /**
+     * Repeated calls to nextDouble produce at least two distinct results
+     */
+    public void testNextDouble() {
+        SplittableRandom sr = new SplittableRandom();
+        double f = sr.nextDouble();
+        int i = 0;
+        while (i < NCALLS && sr.nextDouble() == f)
+            ++i;
+        assertTrue(i < NCALLS);
+    }
+
+    /**
+     * Two SplittableRandoms created with the same seed produce the
+     * same values for nextLong.
+     */
+    public void testSeedConstructor() {
+        for (long seed = 2; seed < MAX_LONG_BOUND; seed += 15485863)  {
+            SplittableRandom sr1 = new SplittableRandom(seed);
+            SplittableRandom sr2 = new SplittableRandom(seed);
+            for (int i = 0; i < REPS; ++i)
+                assertEquals(sr1.nextLong(), sr2.nextLong());
+        }
+    }
+
+    /**
+     * A SplittableRandom produced by split() of a default-constructed
+     * SplittableRandom generates a different sequence
+     */
+    public void testSplit1() {
+        SplittableRandom sr = new SplittableRandom();
+        for (int reps = 0; reps < REPS; ++reps) {
+            SplittableRandom sc = sr.split();
+            int i = 0;
+            while (i < NCALLS && sr.nextLong() == sc.nextLong())
+                ++i;
+            assertTrue(i < NCALLS);
+        }
+    }
+
+    /**
+     * A SplittableRandom produced by split() of a seeded-constructed
+     * SplittableRandom generates a different sequence
+     */
+    public void testSplit2() {
+        SplittableRandom sr = new SplittableRandom(12345);
+        for (int reps = 0; reps < REPS; ++reps) {
+            SplittableRandom sc = sr.split();
+            int i = 0;
+            while (i < NCALLS && sr.nextLong() == sc.nextLong())
+                ++i;
+            assertTrue(i < NCALLS);
+        }
+    }
+
+    /**
+     * nextInt(negative) throws IllegalArgumentException
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testNextIntBoundedNeg() {
+        SplittableRandom sr = new SplittableRandom();
+        int f = sr.nextInt(-17);
+    }
+
+    /**
+     * nextInt(least >= bound) throws IllegalArgumentException
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testNextIntBadBounds() {
+        SplittableRandom sr = new SplittableRandom();
+        int f = sr.nextInt(17, 2);
+    }
+
+    /**
+     * nextInt(bound) returns 0 <= value < bound;
+     * repeated calls produce at least two distinct results
+     */
+    public void testNextIntBounded() {
+        SplittableRandom sr = new SplittableRandom();
+        // sample bound space across prime number increments
+        for (int bound = 2; bound < MAX_INT_BOUND; bound += 524959) {
+            int f = sr.nextInt(bound);
+            assertTrue(0 <= f && f < bound);
+            int i = 0;
+            int j;
+            while (i < NCALLS &&
+                   (j = sr.nextInt(bound)) == f) {
+                assertTrue(0 <= j && j < bound);
+                ++i;
+            }
+            assertTrue(i < NCALLS);
+        }
+    }
+
+    /**
+     * nextInt(least, bound) returns least <= value < bound;
+     * repeated calls produce at least two distinct results
+     */
+    public void testNextIntBounded2() {
+        SplittableRandom sr = new SplittableRandom();
+        for (int least = -15485863; least < MAX_INT_BOUND; least += 524959) {
+            for (int bound = least + 2; bound > least && bound < MAX_INT_BOUND; bound += 49979687) {
+                int f = sr.nextInt(least, bound);
+                assertTrue(least <= f && f < bound);
+                int i = 0;
+                int j;
+                while (i < NCALLS &&
+                       (j = sr.nextInt(least, bound)) == f) {
+                    assertTrue(least <= j && j < bound);
+                    ++i;
+                }
+                assertTrue(i < NCALLS);
+            }
+        }
+    }
+
+    /**
+     * nextLong(negative) throws IllegalArgumentException
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testNextLongBoundedNeg() {
+        SplittableRandom sr = new SplittableRandom();
+        long f = sr.nextLong(-17);
+    }
+
+    /**
+     * nextLong(least >= bound) throws IllegalArgumentException
+     */
+    @Test(expectedExceptions = IllegalArgumentException.class)
+    public void testNextLongBadBounds() {
+        SplittableRandom sr = new SplittableRandom();
+        long f = sr.nextLong(17, 2);
+    }
+
+    /**
+     * nextLong(bound) returns 0 <= value < bound;
+     * repeated calls produce at least two distinct results
+     */
+    public void testNextLongBounded() {
+        SplittableRandom sr = new SplittableRandom();
+        for (long bound = 2; bound < MAX_LONG_BOUND; bound += 15485863) {
+            long f = sr.nextLong(bound);
+            assertTrue(0 <= f && f < bound);
+            int i = 0;
+            long j;
+            while (i < NCALLS &&
+                   (j = sr.nextLong(bound)) == f) {
+                assertTrue(0 <= j && j < bound);
+                ++i;
+            }
+            assertTrue(i < NCALLS);
+        }
+    }
+
+    /**
+     * nextLong(least, bound) returns least <= value < bound;
+     * repeated calls produce at least two distinct results
+     */
+    public void testNextLongBounded2() {
+        SplittableRandom sr = new SplittableRandom();
+        for (long least = -86028121; least < MAX_LONG_BOUND; least += 982451653L) {
+            for (long bound = least + 2; bound > least && bound < MAX_LONG_BOUND; bound += Math.abs(bound * 7919)) {
+                long f = sr.nextLong(least, bound);
+                assertTrue(least <= f && f < bound);
+                int i = 0;
+                long j;
+                while (i < NCALLS &&
+                       (j = sr.nextLong(least, bound)) == f) {
+                    assertTrue(least <= j && j < bound);
+                    ++i;
+                }
+                assertTrue(i < NCALLS);
+            }
+        }
+    }
+
+    /**
+     * nextDouble(least, bound) returns least <= value < bound;
+     * repeated calls produce at least two distinct results
+     */
+    public void testNextDoubleBounded2() {
+        SplittableRandom sr = new SplittableRandom();
+        for (double least = 0.0001; least < 1.0e20; least *= 8) {
+            for (double bound = least * 1.001; bound < 1.0e20; bound *= 16) {
+                double f = sr.nextDouble(least, bound);
+                assertTrue(least <= f && f < bound);
+                int i = 0;
+                double j;
+                while (i < NCALLS &&
+                       (j = sr.nextDouble(least, bound)) == f) {
+                    assertTrue(least <= j && j < bound);
+                    ++i;
+                }
+                assertTrue(i < NCALLS);
+            }
+        }
+    }
+
+    /**
+     * Invoking sized ints, long, doubles, with negative sizes throws
+     * IllegalArgumentException
+     */
+    public void testBadStreamSize() {
+        SplittableRandom r = new SplittableRandom();
+        executeAndCatchIAE(() -> r.ints(-1L));
+        executeAndCatchIAE(() -> r.ints(-1L, 2, 3));
+        executeAndCatchIAE(() -> r.longs(-1L));
+        executeAndCatchIAE(() -> r.longs(-1L, -1L, 1L));
+        executeAndCatchIAE(() -> r.doubles(-1L));
+        executeAndCatchIAE(() -> r.doubles(-1L, .5, .6));
+    }
+
+    /**
+     * Invoking bounded ints, long, doubles, with illegal bounds throws
+     * IllegalArgumentException
+     */
+    public void testBadStreamBounds() {
+        SplittableRandom r = new SplittableRandom();
+        executeAndCatchIAE(() -> r.ints(2, 1));
+        executeAndCatchIAE(() -> r.ints(10, 42, 42));
+        executeAndCatchIAE(() -> r.longs(-1L, -1L));
+        executeAndCatchIAE(() -> r.longs(10, 1L, -2L));
+        executeAndCatchIAE(() -> r.doubles(0.0, 0.0));
+        executeAndCatchIAE(() -> r.doubles(10, .5, .4));
+    }
+
+    private void executeAndCatchIAE(Runnable r) {
+        executeAndCatch(IllegalArgumentException.class, r);
+    }
+
+    private void executeAndCatch(Class<? extends Exception> expected, Runnable r) {
+        Exception caught = null;
+        try {
+            r.run();
+        }
+        catch (Exception e) {
+            caught = e;
+        }
+
+        assertNotNull(caught,
+                      String.format("No Exception was thrown, expected an Exception of %s to be thrown",
+                                    expected.getName()));
+        Assert.assertTrue(expected.isInstance(caught),
+                          String.format("Exception thrown %s not an instance of %s",
+                                        caught.getClass().getName(), expected.getName()));
+    }
+
+    /**
+     * A parallel sized stream of ints generates the given number of values
+     */
+    public void testIntsCount() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 0;
+        for (int reps = 0; reps < REPS; ++reps) {
+            counter.reset();
+            r.ints(size).parallel().forEach(x -> {counter.increment();});
+            assertEquals(counter.sum(), size);
+            size += 524959;
+        }
+    }
+
+    /**
+     * A parallel sized stream of longs generates the given number of values
+     */
+    public void testLongsCount() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 0;
+        for (int reps = 0; reps < REPS; ++reps) {
+            counter.reset();
+            r.longs(size).parallel().forEach(x -> {counter.increment();});
+            assertEquals(counter.sum(), size);
+            size += 524959;
+        }
+    }
+
+    /**
+     * A parallel sized stream of doubles generates the given number of values
+     */
+    public void testDoublesCount() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 0;
+        for (int reps = 0; reps < REPS; ++reps) {
+            counter.reset();
+            r.doubles(size).parallel().forEach(x -> {counter.increment();});
+            assertEquals(counter.sum(), size);
+            size += 524959;
+        }
+    }
+
+    /**
+     * Each of a parallel sized stream of bounded ints is within bounds
+     */
+    public void testBoundedInts() {
+        AtomicInteger fails = new AtomicInteger(0);
+        SplittableRandom r = new SplittableRandom();
+        long size = 12345L;
+        for (int least = -15485867; least < MAX_INT_BOUND; least += 524959) {
+            for (int bound = least + 2; bound > least && bound < MAX_INT_BOUND; bound += 67867967) {
+                final int lo = least, hi = bound;
+                r.ints(size, lo, hi).parallel().
+                    forEach(x -> {if (x < lo || x >= hi)
+                                fails.getAndIncrement(); });
+            }
+        }
+        assertEquals(fails.get(), 0);
+    }
+
+    /**
+     * Each of a parallel sized stream of bounded longs is within bounds
+     */
+    public void testBoundedLongs() {
+        AtomicInteger fails = new AtomicInteger(0);
+        SplittableRandom r = new SplittableRandom();
+        long size = 123L;
+        for (long least = -86028121; least < MAX_LONG_BOUND; least += 1982451653L) {
+            for (long bound = least + 2; bound > least && bound < MAX_LONG_BOUND; bound += Math.abs(bound * 7919)) {
+                final long lo = least, hi = bound;
+                r.longs(size, lo, hi).parallel().
+                    forEach(x -> {if (x < lo || x >= hi)
+                                fails.getAndIncrement(); });
+            }
+        }
+        assertEquals(fails.get(), 0);
+    }
+
+    /**
+     * Each of a parallel sized stream of bounded doubles is within bounds
+     */
+    public void testBoundedDoubles() {
+        AtomicInteger fails = new AtomicInteger(0);
+        SplittableRandom r = new SplittableRandom();
+        long size = 456;
+        for (double least = 0.00011; least < 1.0e20; least *= 9) {
+            for (double bound = least * 1.0011; bound < 1.0e20; bound *= 17) {
+                final double lo = least, hi = bound;
+                r.doubles(size, lo, hi).parallel().
+                    forEach(x -> {if (x < lo || x >= hi)
+                                fails.getAndIncrement(); });
+            }
+        }
+        assertEquals(fails.get(), 0);
+    }
+
+    /**
+     * A parallel unsized stream of ints generates at least 100 values
+     */
+    public void testUnsizedIntsCount() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 100;
+        r.ints().limit(size).parallel().forEach(x -> {counter.increment();});
+        assertEquals(counter.sum(), size);
+    }
+
+    /**
+     * A parallel unsized stream of longs generates at least 100 values
+     */
+    public void testUnsizedLongsCount() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 100;
+        r.longs().limit(size).parallel().forEach(x -> {counter.increment();});
+        assertEquals(counter.sum(), size);
+    }
+
+    /**
+     * A parallel unsized stream of doubles generates at least 100 values
+     */
+    public void testUnsizedDoublesCount() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 100;
+        r.doubles().limit(size).parallel().forEach(x -> {counter.increment();});
+        assertEquals(counter.sum(), size);
+    }
+
+    /**
+     * A sequential unsized stream of ints generates at least 100 values
+     */
+    public void testUnsizedIntsCountSeq() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 100;
+        r.ints().limit(size).forEach(x -> {counter.increment();});
+        assertEquals(counter.sum(), size);
+    }
+
+    /**
+     * A sequential unsized stream of longs generates at least 100 values
+     */
+    public void testUnsizedLongsCountSeq() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 100;
+        r.longs().limit(size).forEach(x -> {counter.increment();});
+        assertEquals(counter.sum(), size);
+    }
+
+    /**
+     * A sequential unsized stream of doubles generates at least 100 values
+     */
+    public void testUnsizedDoublesCountSeq() {
+        LongAdder counter = new LongAdder();
+        SplittableRandom r = new SplittableRandom();
+        long size = 100;
+        r.doubles().limit(size).forEach(x -> {counter.increment();});
+        assertEquals(counter.sum(), size);
+    }
+
+}

test/java/util/stream/test/org/openjdk/tests/java/util/SplittableRandomTest.java

+/*
+ * 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.
+ *
+ * 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 org.openjdk.tests.java.util;
+
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.SplittableRandom;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.stream.DoubleStream;
+import java.util.stream.DoubleStreamTestScenario;
+import java.util.stream.IntStream;
+import java.util.stream.IntStreamTestScenario;
+import java.util.stream.LongStream;
+import java.util.stream.LongStreamTestScenario;
+import java.util.stream.OpTestCase;
+import java.util.stream.StreamSupport;
+import java.util.stream.TestData;
+
+@Test
+public class SplittableRandomTest extends OpTestCase {
+
+    static class RandomBoxedSpliterator<T> implements Spliterator<T> {
+        final SplittableRandom rng;
+        long index;
+        final long fence;
+        final Function<SplittableRandom, T> rngF;
+
+        RandomBoxedSpliterator(SplittableRandom rng, long index, long fence, Function<SplittableRandom, T> rngF) {
+            this.rng = rng;
+            this.index = index;
+            this.fence = fence;
+            this.rngF = rngF;
+        }
+
+        public RandomBoxedSpliterator<T> trySplit() {
+            long i = index, m = (i + fence) >>> 1;
+            return (m <= i) ? null :
+                   new RandomBoxedSpliterator<>(rng.split(), i, index = m, rngF);
+        }
+
+        public long estimateSize() {
+            return fence - index;
+        }
+
+        public int characteristics() {
+            return (Spliterator.SIZED | Spliterator.SUBSIZED |
+                    Spliterator.NONNULL | Spliterator.IMMUTABLE);
+        }
+
+        @Override
+        public boolean tryAdvance(Consumer<? super T> consumer) {
+            if (consumer == null) throw new NullPointerException();
+            long i = index, f = fence;
+            if (i < f) {
+                consumer.accept(rngF.apply(rng));
+                index = i + 1;
+                return true;
+            }
+            return false;
+        }
+    }
+
+    static final int SIZE = 1 << 16;
+
+    // Ensure there is a range of a power of 2
+    static final int[] BOUNDS = {256};
+    static final int[] ORIGINS = {-16, 0, 16};
+
+    static <T extends Comparable<T>> ResultAsserter<Iterable<T>> randomAsserter(int size, T origin, T bound) {
+        return (act, exp, ord, par) -> {
+            int count = 0;
+            Set<Comparable<T>> values = new HashSet<>();
+            for (Comparable<T> t : act) {
+                if (origin.compareTo(bound) < 0) {
+                    assertTrue(t.compareTo(origin) >= 0);
+                    assertTrue(t.compareTo(bound) < 0);
+                }
+                values.add(t);
+                count++;
+            }
+            assertEquals(count, size);
+            // Assert that at least one different result is produced
+            // For the size of the data it is highly improbable that this
+            // will cause a false negative (i.e. a false failure)
+            assertTrue(values.size() > 1);
+        };
+    }
+
+    @DataProvider(name = "ints")
+    public static Object[][] intsDataProvider() {
+        List<Object[]> data = new ArrayList<>();
+
+        // Function to create a stream using a RandomBoxedSpliterator
+
+        Function<Function<SplittableRandom, Integer>, IntStream> rbsf =
+                sf -> StreamSupport.stream(new RandomBoxedSpliterator<>(new SplittableRandom(), 0, SIZE, sf), false).
+                        mapToInt(i -> i);
+
+        // Unbounded
+
+        data.add(new Object[]{
+                TestData.Factory.ofIntSupplier(
+                        String.format("new SplittableRandom().ints().limit(%d)", SIZE),
+                        () -> new SplittableRandom().ints().limit(SIZE)),
+                randomAsserter(SIZE, Integer.MAX_VALUE, 0)
+        });
+
+        data.add(new Object[]{
+                TestData.Factory.ofIntSupplier(
+                        String.format("new SplittableRandom().ints(%d)", SIZE),
+                        () -> new SplittableRandom().ints(SIZE)),
+                randomAsserter(SIZE, Integer.MAX_VALUE, 0)
+        });
+
+        data.add(new Object[]{
+                TestData.Factory.ofIntSupplier(
+                        String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextInt())", SIZE),
+                        () -> rbsf.apply(sr -> sr.nextInt())),
+                randomAsserter(SIZE, Integer.MAX_VALUE, 0)
+        });
+
+        // Bounded
+
+        for (int b : BOUNDS) {
+            for (int o : ORIGINS) {
+                final int origin = o;
+                final int bound = b;
+
+                data.add(new Object[]{
+                        TestData.Factory.ofIntSupplier(
+                                String.format("new SplittableRandom().ints(%d, %d).limit(%d)", origin, bound, SIZE),
+                                () -> new SplittableRandom().ints(origin, bound).limit(SIZE)),
+                        randomAsserter(SIZE, origin, bound)
+                });
+
+                data.add(new Object[]{
+                        TestData.Factory.ofIntSupplier(
+                                String.format("new SplittableRandom().ints(%d, %d, %d)", SIZE, origin, bound),
+                                () -> new SplittableRandom().ints(SIZE, origin, bound)),
+                        randomAsserter(SIZE, origin, bound)
+                });
+
+                if (origin == 0) {
+                    data.add(new Object[]{
+                            TestData.Factory.ofIntSupplier(
+                                    String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextInt(%d))", SIZE, bound),
+                                    () -> rbsf.apply(sr -> sr.nextInt(bound))),
+                            randomAsserter(SIZE, origin, bound)
+                    });
+                }
+
+                data.add(new Object[]{
+                        TestData.Factory.ofIntSupplier(
+                                String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextInt(%d, %d))", SIZE, origin, bound),
+                                () -> rbsf.apply(sr -> sr.nextInt(origin, bound))),
+                        randomAsserter(SIZE, origin, bound)
+                });
+            }
+        }
+
+        return data.toArray(new Object[0][]);
+    }
+
+    @Test(dataProvider = "ints")
+    public void testInts(TestData.OfInt data, ResultAsserter<Iterable<Integer>> ra) {
+        withData(data).
+                stream(s -> s).
+                without(IntStreamTestScenario.PAR_STREAM_TO_ARRAY_CLEAR_SIZED).
+                resultAsserter(ra).
+                exercise();
+    }
+
+    @DataProvider(name = "longs")
+    public static Object[][] longsDataProvider() {
+        List<Object[]> data = new ArrayList<>();
+
+        // Function to create a stream using a RandomBoxedSpliterator
+
+        Function<Function<SplittableRandom, Long>, LongStream> rbsf =
+                sf -> StreamSupport.stream(new RandomBoxedSpliterator<>(new SplittableRandom(), 0, SIZE, sf), false).
+                        mapToLong(i -> i);
+
+        // Unbounded
+
+        data.add(new Object[]{
+                TestData.Factory.ofLongSupplier(
+                        String.format("new SplittableRandom().longs().limit(%d)", SIZE),
+                        () -> new SplittableRandom().longs().limit(SIZE)),
+                randomAsserter(SIZE, Long.MAX_VALUE, 0L)
+        });
+
+        data.add(new Object[]{
+                TestData.Factory.ofLongSupplier(
+                        String.format("new SplittableRandom().longs(%d)", SIZE),
+                        () -> new SplittableRandom().longs(SIZE)),
+                randomAsserter(SIZE, Long.MAX_VALUE, 0L)
+        });
+
+        data.add(new Object[]{
+                TestData.Factory.ofLongSupplier(
+                        String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextLong())", SIZE),
+                        () -> rbsf.apply(sr -> sr.nextLong())),
+                randomAsserter(SIZE, Long.MAX_VALUE, 0L)
+        });
+
+        // Bounded
+
+        for (int b : BOUNDS) {
+            for (int o : ORIGINS) {
+                final long origin = o;
+                final long bound = b;
+
+                data.add(new Object[]{
+                        TestData.Factory.ofLongSupplier(
+                                String.format("new SplittableRandom().longs(%d, %d).limit(%d)", origin, bound, SIZE),
+                                () -> new SplittableRandom().longs(origin, bound).limit(SIZE)),
+                        randomAsserter(SIZE, origin, bound)
+                });
+
+                data.add(new Object[]{
+                        TestData.Factory.ofLongSupplier(
+                                String.format("new SplittableRandom().longs(%d, %d, %d)", SIZE, origin, bound),
+                                () -> new SplittableRandom().longs(SIZE, origin, bound)),
+                        randomAsserter(SIZE, origin, bound)
+                });
+
+                if (origin == 0) {
+                    data.add(new Object[]{
+                            TestData.Factory.ofLongSupplier(
+                                    String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextLong(%d))", SIZE, bound),
+                                    () -> rbsf.apply(sr -> sr.nextLong(bound))),
+                            randomAsserter(SIZE, origin, bound)
+                    });
+                }
+
+                data.add(new Object[]{
+                        TestData.Factory.ofLongSupplier(
+                                String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextLong(%d, %d))", SIZE, origin, bound),
+                                () -> rbsf.apply(sr -> sr.nextLong(origin, bound))),
+                        randomAsserter(SIZE, origin, bound)
+                });
+            }
+        }
+
+        return data.toArray(new Object[0][]);
+    }
+
+    @Test(dataProvider = "longs")
+    public void testLongs(TestData.OfLong data, ResultAsserter<Iterable<Long>> ra) {
+        withData(data).
+                stream(s -> s).
+                without(LongStreamTestScenario.PAR_STREAM_TO_ARRAY_CLEAR_SIZED).
+                resultAsserter(ra).
+                exercise();
+    }
+
+    @DataProvider(name = "doubles")
+    public static Object[][] doublesDataProvider() {
+        List<Object[]> data = new ArrayList<>();
+
+        // Function to create a stream using a RandomBoxedSpliterator
+
+        Function<Function<SplittableRandom, Double>, DoubleStream> rbsf =
+                sf -> StreamSupport.stream(new RandomBoxedSpliterator<>(new SplittableRandom(), 0, SIZE, sf), false).
+                        mapToDouble(i -> i);
+
+        // Unbounded
+
+        data.add(new Object[]{
+                TestData.Factory.ofDoubleSupplier(
+                        String.format("new SplittableRandom().doubles().limit(%d)", SIZE),
+                        () -> new SplittableRandom().doubles().limit(SIZE)),
+                randomAsserter(SIZE, Double.MAX_VALUE, 0d)
+        });
+
+        data.add(new Object[]{
+                TestData.Factory.ofDoubleSupplier(
+                        String.format("new SplittableRandom().doubles(%d)", SIZE),
+                        () -> new SplittableRandom().doubles(SIZE)),
+                randomAsserter(SIZE, Double.MAX_VALUE, 0d)
+        });
+
+        data.add(new Object[]{
+                TestData.Factory.ofDoubleSupplier(
+                        String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextDouble())", SIZE),
+                        () -> rbsf.apply(sr -> sr.nextDouble())),
+                randomAsserter(SIZE, Double.MAX_VALUE, 0d)
+        });
+
+        // Bounded
+
+        for (int b : BOUNDS) {
+            for (int o : ORIGINS) {
+                final double origin = o;
+                final double bound = b;
+
+                data.add(new Object[]{
+                        TestData.Factory.ofDoubleSupplier(
+                                String.format("new SplittableRandom().doubles(%f, %f).limit(%d)", origin, bound, SIZE),
+                                () -> new SplittableRandom().doubles(origin, bound).limit(SIZE)),
+                        randomAsserter(SIZE, origin, bound)
+                });
+
+                data.add(new Object[]{
+                        TestData.Factory.ofDoubleSupplier(
+                                String.format("new SplittableRandom().doubles(%d, %f, %f)", SIZE, origin, bound),
+                                () -> new SplittableRandom().doubles(SIZE, origin, bound)),
+                        randomAsserter(SIZE, origin, bound)
+                });
+
+                if (origin == 0) {
+                    data.add(new Object[]{
+                            TestData.Factory.ofDoubleSupplier(
+                                    String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextDouble(%f))", SIZE, bound),
+                                    () -> rbsf.apply(sr -> sr.nextDouble(bound))),
+                            randomAsserter(SIZE, origin, bound)
+                    });
+                }
+
+                data.add(new Object[]{
+                        TestData.Factory.ofDoubleSupplier(
+                                String.format("new RandomBoxedSpliterator(0, %d, sr -> sr.nextDouble(%f, %f))", SIZE, origin, bound),
+                                () -> rbsf.apply(sr -> sr.nextDouble(origin, bound))),
+                        randomAsserter(SIZE, origin, bound)
+                });
+            }
+        }
+
+        return data.toArray(new Object[0][]);
+    }
+
+    @Test(dataProvider = "doubles")
+    public void testDoubles(TestData.OfDouble data, ResultAsserter<Iterable<Double>> ra) {
+        withData(data).
+                stream(s -> s).
+                without(DoubleStreamTestScenario.PAR_STREAM_TO_ARRAY_CLEAR_SIZED).
+                resultAsserter(ra).
+                exercise();
+    }
+}