diff -r c646b256fbcc -r 6d87e9f7a1ec newrandom/ThreadLocalRandom.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/newrandom/ThreadLocalRandom.java	Thu May 23 16:45:56 2019 -0400
@@ -0,0 +1,386 @@
+/*
+ * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ */
+
+/*
+ *
+ *
+ *
+ *
+ *
+ * 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.math.BigInteger;
+// import java.util.Random;
+import java.util.Spliterator;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * A random number generator isolated to the current thread.  Like the
+ * global {@link java.util.Random} generator used by the {@link
+ * java.lang.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.
+     */
+
+    /** Generates per-thread initialization/probe field */
+    private static final AtomicInteger probeGenerator =
+        new AtomicInteger();
+
+    /**
+     * The next seed for default constructors.
+     */
+    private static final AtomicLong seeder = new AtomicLong(RngSupport.initialSeed());
+
+    /**
+     * 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)
+
+    /** Rarely-used holder for the second of a pair of Gaussians */
+    private static final ThreadLocal<Double> nextLocalGaussian =
+        new ThreadLocal<Double>();
+
+    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
+    }
+
+    /** The common ThreadLocalRandom */
+    static final ThreadLocalRandom instance = new ThreadLocalRandom();
+
+    /**
+     * 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();
+        UNSAFE.putLong(t, SEED, seed);
+        UNSAFE.putInt(t, PROBE, probe);
+    }
+
+    /**
+     * Returns the current thread's {@code ThreadLocalRandom}.
+     *
+     * @return the current thread's {@code ThreadLocalRandom}
+     */
+    public static ThreadLocalRandom current() {
+        if (UNSAFE.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
+        UNSAFE.putLong(t = Thread.currentThread(), SEED,
+                       r = UNSAFE.getLong(t, SEED) + GAMMA);
+        return r;
+    }
+
+    // We must define this (to override the definition inherited from
+    // class Random), but we don't use it from within other methods.
+    protected int next(int bits) {
+        return (int)(mix64(nextSeed()) >>> (64 - bits));
+    }
+
+    /**
+     * Returns a pseudorandom {@code int} value.
+     *
+     * @return a pseudorandom {@code int} value
+     */
+    public int nextInt() {
+        return mix32(nextSeed());
+    }
+
+    /**
+     * Returns a pseudorandom {@code long} value.
+     *
+     * @return a pseudorandom {@code long} value
+     */
+    public long nextLong() {
+        return mix64(nextSeed());
+    }
+
+    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;
+    }
+
+    static final BigInteger thePeriod = BigInteger.valueOf(1).shiftLeft(64);  // Period is 2**64
+    public BigInteger period() { return thePeriod; }
+
+    // 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 UNSAFE.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;
+        UNSAFE.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 = UNSAFE.getInt(t, SECONDARY)) != 0) {
+            r ^= r << 13;   // xorshift
+            r ^= r >>> 17;
+            r ^= r << 5;
+        }
+        else {
+            localInit();
+            if ((r = (int)UNSAFE.getLong(t, SEED)) == 0)
+                r = 1; // avoid zero
+        }
+        UNSAFE.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", UNSAFE.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();
+    }
+
+    // Unsafe mechanics
+    private static final sun.misc.Unsafe UNSAFE;
+    private static final long SEED;
+    private static final long PROBE;
+    private static final long SECONDARY;
+    static {
+        try {
+            UNSAFE = sun.misc.Unsafe.getUnsafe();
+            Class<?> tk = Thread.class;
+            SEED = UNSAFE.objectFieldOffset
+                (tk.getDeclaredField("threadLocalRandomSeed"));
+            PROBE = UNSAFE.objectFieldOffset
+                (tk.getDeclaredField("threadLocalRandomProbe"));
+            SECONDARY = UNSAFE.objectFieldOffset
+                (tk.getDeclaredField("threadLocalRandomSecondarySeed"));
+        } catch (Exception e) {
+            throw new Error(e);
+        }
+    }
+}