content: /*
   * 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.
   */
  
  /*
   * This file is available under and governed by the GNU General Public
   * License version 2 only, as published by the Free Software Foundation.
   * However, the following notice accompanied the original version of this
   * file:
   *
   * Written by Doug Lea with assistance from members of JCP JSR-166
   * Expert Group and released to the public domain, as explained at
   * http://creativecommons.org/publicdomain/zero/1.0/
   */
  
  package java.util.concurrent;
  
  import java.io.ObjectStreamField;
  import java.util.Random;
  import java.util.Spliterator;
  import java.util.concurrent.atomic.AtomicInteger;
  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 random number generator isolated to the current thread.  Like the
   * global {@link Random} generator used by the {@link
   * Math} class, a {@code ThreadLocalRandom} is initialized
   * with an internally generated seed that may not otherwise be
   * modified. When applicable, use of {@code ThreadLocalRandom} rather
   * than shared {@code Random} objects in concurrent programs will
   * typically encounter much less overhead and contention.  Use of
   * {@code ThreadLocalRandom} is particularly appropriate when multiple
   * tasks (for example, each a {@link ForkJoinTask}) use random numbers
   * in parallel in thread pools.
   *
   * <p>Usages of this class should typically be of the form:
   * {@code ThreadLocalRandom.current().nextX(...)} (where
   * {@code X} is {@code Int}, {@code Long}, etc).
   * When all usages are of this form, it is never possible to
   * accidently share a {@code ThreadLocalRandom} across multiple threads.
   *
   * <p>This class also provides additional commonly used bounded random
   * generation methods.
   *
   * <p>Instances of {@code ThreadLocalRandom} 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}.
   *
   * @since 1.7
   * @author Doug Lea
   */
  public class ThreadLocalRandom extends Random {
      /*
       * This class implements the java.util.Random API (and subclasses
       * Random) using a single static instance that accesses random
       * number state held in class Thread (primarily, field
       * threadLocalRandomSeed). In doing so, it also provides a home
       * for managing package-private utilities that rely on exactly the
       * same state as needed to maintain the ThreadLocalRandom
       * instances. We leverage the need for an initialization flag
       * field to also use it as a "probe" -- a self-adjusting thread
       * hash used for contention avoidance, as well as a secondary
       * simpler (xorShift) random seed that is conservatively used to
       * avoid otherwise surprising users by hijacking the
       * ThreadLocalRandom sequence.  The dual use is a marriage of
       * convenience, but is a simple and efficient way of reducing
       * application-level overhead and footprint of most concurrent
       * programs.
       *
       * Even though this class subclasses java.util.Random, it uses the
       * same basic algorithm as java.util.SplittableRandom.  (See its
       * internal documentation for explanations, which are not repeated
       * here.)  Because ThreadLocalRandoms are not splittable
       * though, we use only a single 64bit gamma.
       *
       * Because this class is in a different package than class Thread,
       * field access methods use Unsafe to bypass access control rules.
       * To conform to the requirements of the Random superclass
       * constructor, the common static ThreadLocalRandom maintains an
       * "initialized" field for the sake of rejecting user calls to
       * setSeed while still allowing a call from constructor.  Note
       * that serialization is completely unnecessary because there is
       * only a static singleton.  But we generate a serial form
       * containing "rnd" and "initialized" fields to ensure
       * compatibility across versions.
       *
       * Implementations of non-core methods are mostly the same as in
       * SplittableRandom, that were in part derived from a previous
       * version of this class.
       *
       * The nextLocalGaussian ThreadLocal supports the very rarely used
       * nextGaussian method by providing a holder for the second of a
       * pair of them. As is true for the base class version of this
       * method, this time/space tradeoff is probably never worthwhile,
       * but we provide identical statistical properties.
       */
  
      private static long mix64(long z) {
          z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
          z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
          return z ^ (z >>> 33);
      }
  
      private static int mix32(long z) {
          z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
          return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
      }
  
      /**
       * Field used only during singleton initialization.
       * True when constructor completes.
       */
      boolean initialized;
  
      /** Constructor used only for static singleton */
      private ThreadLocalRandom() {
          initialized = true; // false during super() call
      }
  
      /**
       * Initialize Thread fields for the current thread.  Called only
       * when Thread.threadLocalRandomProbe is zero, indicating that a
       * thread local seed value needs to be generated. Note that even
       * though the initialization is purely thread-local, we need to
       * rely on (static) atomic generators to initialize the values.
       */
      static final void localInit() {
          int p = probeGenerator.addAndGet(PROBE_INCREMENT);
          int probe = (p == 0) ? 1 : p; // skip 0
          long seed = mix64(seeder.getAndAdd(SEEDER_INCREMENT));
          Thread t = Thread.currentThread();
          U.putLong(t, SEED, seed);
          U.putInt(t, PROBE, probe);
      }
  
      /**
       * Returns the current thread's {@code ThreadLocalRandom}.
       *
       * @return the current thread's {@code ThreadLocalRandom}
       */
      public static ThreadLocalRandom current() {
          if (U.getInt(Thread.currentThread(), PROBE) == 0)
              localInit();
          return instance;
      }
  
      /**
       * Throws {@code UnsupportedOperationException}.  Setting seeds in
       * this generator is not supported.
       *
       * @throws UnsupportedOperationException always
       */
      public void setSeed(long seed) {
          // only allow call from super() constructor
          if (initialized)
              throw new UnsupportedOperationException();
      }
  
      final long nextSeed() {
          Thread t; long r; // read and update per-thread seed
          U.putLong(t = Thread.currentThread(), SEED,
                    r = U.getLong(t, SEED) + GAMMA);
          return r;
      }
  
      // We must define this, but never use it.
      protected int next(int bits) {
          return (int)(mix64(nextSeed()) >>> (64 - bits));
      }
  
      /**
       * 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) {
          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;
      }
  
      /**
       * 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);
          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);
          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;
      }
  
      /**
       * Returns a pseudorandom {@code float} value between zero
       * (inclusive) and one (exclusive).
       *
       * @return a pseudorandom {@code float} value between zero
       *         (inclusive) and one (exclusive)
       */
      public float nextFloat() {
          return (mix32(nextSeed()) >>> 8) * FLOAT_UNIT;
      }
  
      public double nextGaussian() {
          // Use nextLocalGaussian instead of nextGaussian field
          Double d = nextLocalGaussian.get();
          if (d != null) {
              nextLocalGaussian.set(null);
              return d.doubleValue();
          }
          double v1, v2, s;
          do {
              v1 = 2 * nextDouble() - 1; // between -1 and 1
              v2 = 2 * nextDouble() - 1; // between -1 and 1
              s = v1 * v1 + v2 * v2;
          } while (s >= 1 || s == 0);
          double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
          nextLocalGaussian.set(new Double(v2 * multiplier));
          return v1 * multiplier;
      }
  
      // 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.
       *
       * @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
       * @since 1.8
       */
      public IntStream ints(long streamSize) {
          if (streamSize < 0L)
              throw new IllegalArgumentException(BAD_SIZE);
          return StreamSupport.intStream
              (new RandomIntsSpliterator
               (0L, streamSize, Integer.MAX_VALUE, 0),
               false);
      }
  
      /**
       * Returns an effectively unlimited stream of pseudorandom {@code int}
       * values.
       *
       * @implNote This method is implemented to be equivalent to {@code
       * ints(Long.MAX_VALUE)}.
       *
       * @return a stream of pseudorandom {@code int} values
       * @since 1.8
       */
      public IntStream ints() {
          return StreamSupport.intStream
              (new RandomIntsSpliterator
               (0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
               false);
      }
  
      /**
       * Returns a stream producing the given {@code streamSize} number
       * of pseudorandom {@code int} values, each conforming 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}
       * @since 1.8
       */
      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
               (0L, streamSize, randomNumberOrigin, randomNumberBound),
               false);
      }
  
      /**
       * Returns an effectively unlimited stream of pseudorandom {@code
       * int} values, each conforming 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}
       * @since 1.8
       */
      public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
          if (randomNumberOrigin >= randomNumberBound)
              throw new IllegalArgumentException(BAD_RANGE);
          return StreamSupport.intStream
              (new RandomIntsSpliterator
               (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
               false);
      }
  
      /**
       * Returns a stream producing the given {@code streamSize} number of
       * pseudorandom {@code long} values.
       *
       * @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
       * @since 1.8
       */
      public LongStream longs(long streamSize) {
          if (streamSize < 0L)
              throw new IllegalArgumentException(BAD_SIZE);
          return StreamSupport.longStream
              (new RandomLongsSpliterator
               (0L, streamSize, Long.MAX_VALUE, 0L),
               false);
      }
  
      /**
       * Returns an effectively unlimited stream of pseudorandom {@code long}
       * values.
       *
       * @implNote This method is implemented to be equivalent to {@code
       * longs(Long.MAX_VALUE)}.
       *
       * @return a stream of pseudorandom {@code long} values
       * @since 1.8
       */
      public LongStream longs() {
          return StreamSupport.longStream
              (new RandomLongsSpliterator
               (0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
               false);
      }
  
      /**
       * Returns a stream producing the given {@code streamSize} number of
       * pseudorandom {@code long}, each conforming 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}
       * @since 1.8
       */
      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
               (0L, streamSize, randomNumberOrigin, randomNumberBound),
               false);
      }
  
      /**
       * Returns an effectively unlimited stream of pseudorandom {@code
       * long} values, each conforming 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}
       * @since 1.8
       */
      public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
          if (randomNumberOrigin >= randomNumberBound)
              throw new IllegalArgumentException(BAD_RANGE);
          return StreamSupport.longStream
              (new RandomLongsSpliterator
               (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
               false);
      }
  
      /**
       * Returns a stream producing the given {@code streamSize} number of
       * pseudorandom {@code double} values, each 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
       * @since 1.8
       */
      public DoubleStream doubles(long streamSize) {
          if (streamSize < 0L)
              throw new IllegalArgumentException(BAD_SIZE);
          return StreamSupport.doubleStream
              (new RandomDoublesSpliterator
               (0L, streamSize, Double.MAX_VALUE, 0.0),
               false);
      }
  
      /**
       * Returns an effectively unlimited stream of pseudorandom {@code
       * double} values, each 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
       * @since 1.8
       */
      public DoubleStream doubles() {
          return StreamSupport.doubleStream
              (new RandomDoublesSpliterator
               (0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
               false);
      }
  
      /**
       * Returns a stream producing the given {@code streamSize} number of
       * pseudorandom {@code double} values, each conforming 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}
       * @since 1.8
       */
      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
               (0L, streamSize, randomNumberOrigin, randomNumberBound),
               false);
      }
  
      /**
       * Returns an effectively unlimited stream of pseudorandom {@code
       * double} values, each conforming 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}
       * @since 1.8
       */
      public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
          if (!(randomNumberOrigin < randomNumberBound))
              throw new IllegalArgumentException(BAD_RANGE);
          return StreamSupport.doubleStream
              (new RandomDoublesSpliterator
               (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 {
          long index;
          final long fence;
          final int origin;
          final int bound;
          RandomIntsSpliterator(long index, long fence,
                                int origin, int bound) {
              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(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(ThreadLocalRandom.current().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;
                  int o = origin, b = bound;
                  ThreadLocalRandom rng = ThreadLocalRandom.current();
                  do {
                      consumer.accept(rng.internalNextInt(o, b));
                  } while (++i < f);
              }
          }
      }
  
      /**
       * Spliterator for long streams.
       */
      private static final class RandomLongsSpliterator
              implements Spliterator.OfLong {
          long index;
          final long fence;
          final long origin;
          final long bound;
          RandomLongsSpliterator(long index, long fence,
                                 long origin, long bound) {
              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(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(ThreadLocalRandom.current().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;
                  long o = origin, b = bound;
                  ThreadLocalRandom rng = ThreadLocalRandom.current();
                  do {
                      consumer.accept(rng.internalNextLong(o, b));
                  } while (++i < f);
              }
          }
  
      }
  
      /**
       * Spliterator for double streams.
       */
      private static final class RandomDoublesSpliterator
              implements Spliterator.OfDouble {
          long index;
          final long fence;
          final double origin;
          final double bound;
          RandomDoublesSpliterator(long index, long fence,
                                   double origin, double bound) {
              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(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(ThreadLocalRandom.current().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;
                  double o = origin, b = bound;
                  ThreadLocalRandom rng = ThreadLocalRandom.current();
                  do {
                      consumer.accept(rng.internalNextDouble(o, b));
                  } while (++i < f);
              }
          }
      }
  
  
      // Within-package utilities
  
      /*
       * Descriptions of the usages of the methods below can be found in
       * the classes that use them. Briefly, a thread's "probe" value is
       * a non-zero hash code that (probably) does not collide with
       * other existing threads with respect to any power of two
       * collision space. When it does collide, it is pseudo-randomly
       * adjusted (using a Marsaglia XorShift). The nextSecondarySeed
       * method is used in the same contexts as ThreadLocalRandom, but
       * only for transient usages such as random adaptive spin/block
       * sequences for which a cheap RNG suffices and for which it could
       * in principle disrupt user-visible statistical properties of the
       * main ThreadLocalRandom if we were to use it.
       *
       * Note: Because of package-protection issues, versions of some
       * these methods also appear in some subpackage classes.
       */
  
      /**
       * Returns the probe value for the current thread without forcing
       * initialization. Note that invoking ThreadLocalRandom.current()
       * can be used to force initialization on zero return.
       */
      static final int getProbe() {
          return U.getInt(Thread.currentThread(), PROBE);
      }
  
      /**
       * Pseudo-randomly advances and records the given probe value for the
       * given thread.
       */
      static final int advanceProbe(int probe) {
          probe ^= probe << 13;   // xorshift
          probe ^= probe >>> 17;
          probe ^= probe << 5;
          U.putInt(Thread.currentThread(), PROBE, probe);
          return probe;
      }
  
      /**
       * Returns the pseudo-randomly initialized or updated secondary seed.
       */
      static final int nextSecondarySeed() {
          int r;
          Thread t = Thread.currentThread();
          if ((r = U.getInt(t, SECONDARY)) != 0) {
              r ^= r << 13;   // xorshift
              r ^= r >>> 17;
              r ^= r << 5;
          }
          else if ((r = mix32(seeder.getAndAdd(SEEDER_INCREMENT))) == 0)
              r = 1; // avoid zero
          U.putInt(t, SECONDARY, r);
          return r;
      }
  
      // Serialization support
  
      private static final long serialVersionUID = -5851777807851030925L;
  
      /**
       * @serialField rnd long
       *              seed for random computations
       * @serialField initialized boolean
       *              always true
       */
      private static final ObjectStreamField[] serialPersistentFields = {
          new ObjectStreamField("rnd", long.class),
          new ObjectStreamField("initialized", boolean.class),
      };
  
      /**
       * Saves the {@code ThreadLocalRandom} to a stream (that is, serializes it).
       * @param s the stream
       * @throws java.io.IOException if an I/O error occurs
       */
      private void writeObject(java.io.ObjectOutputStream s)
          throws java.io.IOException {
  
          java.io.ObjectOutputStream.PutField fields = s.putFields();
          fields.put("rnd", U.getLong(Thread.currentThread(), SEED));
          fields.put("initialized", true);
          s.writeFields();
      }
  
      /**
       * Returns the {@link #current() current} thread's {@code ThreadLocalRandom}.
       * @return the {@link #current() current} thread's {@code ThreadLocalRandom}
       */
      private Object readResolve() {
          return current();
      }
  
      // Static initialization
  
      /**
       * The seed increment.
       */
      private static final long GAMMA = 0x9e3779b97f4a7c15L;
  
      /**
       * The increment for generating probe values.
       */
      private static final int PROBE_INCREMENT = 0x9e3779b9;
  
      /**
       * The increment of seeder per new instance.
       */
      private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL;
  
      // Constants from SplittableRandom
      private static final double DOUBLE_UNIT = 0x1.0p-53;  // 1.0  / (1L << 53)
      private static final float  FLOAT_UNIT  = 0x1.0p-24f; // 1.0f / (1 << 24)
  
      // 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";
  
      // Unsafe mechanics
      private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe();
      private static final long SEED;
      private static final long PROBE;
      private static final long SECONDARY;
      static {
          try {
              SEED = U.objectFieldOffset
                  (Thread.class.getDeclaredField("threadLocalRandomSeed"));
              PROBE = U.objectFieldOffset
                  (Thread.class.getDeclaredField("threadLocalRandomProbe"));
              SECONDARY = U.objectFieldOffset
                  (Thread.class.getDeclaredField("threadLocalRandomSecondarySeed"));
          } catch (ReflectiveOperationException e) {
              throw new Error(e);
          }
      }
  
      /** Rarely-used holder for the second of a pair of Gaussians */
      private static final ThreadLocal<Double> nextLocalGaussian =
          new ThreadLocal<>();
  
      /** Generates per-thread initialization/probe field */
      private static final AtomicInteger probeGenerator = new AtomicInteger();
  
      /** The common ThreadLocalRandom */
      static final ThreadLocalRandom instance = new ThreadLocalRandom();
  
      /**
       * The next seed for default constructors.
       */
      private static final AtomicLong seeder
          = 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);
              seeder.set(s);
          }
      }
  }
  