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   * 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 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);
      }
  
      /**
       * 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);
              }
          }
      }
  
  }
  