1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/ThreadLocalRandom.java Sat Mar 19 10:46:31 2016 +0100
1.3 @@ -0,0 +1,226 @@
1.4 +/*
1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.6 + *
1.7 + * This code is free software; you can redistribute it and/or modify it
1.8 + * under the terms of the GNU General Public License version 2 only, as
1.9 + * published by the Free Software Foundation. Oracle designates this
1.10 + * particular file as subject to the "Classpath" exception as provided
1.11 + * by Oracle in the LICENSE file that accompanied this code.
1.12 + *
1.13 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.14 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.15 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.16 + * version 2 for more details (a copy is included in the LICENSE file that
1.17 + * accompanied this code).
1.18 + *
1.19 + * You should have received a copy of the GNU General Public License version
1.20 + * 2 along with this work; if not, write to the Free Software Foundation,
1.21 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.22 + *
1.23 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.24 + * or visit www.oracle.com if you need additional information or have any
1.25 + * questions.
1.26 + */
1.27 +
1.28 +/*
1.29 + * This file is available under and governed by the GNU General Public
1.30 + * License version 2 only, as published by the Free Software Foundation.
1.31 + * However, the following notice accompanied the original version of this
1.32 + * file:
1.33 + *
1.34 + * Written by Doug Lea with assistance from members of JCP JSR-166
1.35 + * Expert Group and released to the public domain, as explained at
1.36 + * http://creativecommons.org/publicdomain/zero/1.0/
1.37 + */
1.38 +
1.39 +package java.util.concurrent;
1.40 +
1.41 +import java.util.Random;
1.42 +
1.43 +/**
1.44 + * A random number generator isolated to the current thread. Like the
1.45 + * global {@link java.util.Random} generator used by the {@link
1.46 + * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized
1.47 + * with an internally generated seed that may not otherwise be
1.48 + * modified. When applicable, use of {@code ThreadLocalRandom} rather
1.49 + * than shared {@code Random} objects in concurrent programs will
1.50 + * typically encounter much less overhead and contention. Use of
1.51 + * {@code ThreadLocalRandom} is particularly appropriate when multiple
1.52 + * tasks (for example, each a {@link ForkJoinTask}) use random numbers
1.53 + * in parallel in thread pools.
1.54 + *
1.55 + * <p>Usages of this class should typically be of the form:
1.56 + * {@code ThreadLocalRandom.current().nextX(...)} (where
1.57 + * {@code X} is {@code Int}, {@code Long}, etc).
1.58 + * When all usages are of this form, it is never possible to
1.59 + * accidently share a {@code ThreadLocalRandom} across multiple threads.
1.60 + *
1.61 + * <p>This class also provides additional commonly used bounded random
1.62 + * generation methods.
1.63 + *
1.64 + * @since 1.7
1.65 + * @author Doug Lea
1.66 + */
1.67 +public class ThreadLocalRandom extends Random {
1.68 + // same constants as Random, but must be redeclared because private
1.69 + private static final long multiplier = 0x5DEECE66DL;
1.70 + private static final long addend = 0xBL;
1.71 + private static final long mask = (1L << 48) - 1;
1.72 +
1.73 + /**
1.74 + * The random seed. We can't use super.seed.
1.75 + */
1.76 + private long rnd;
1.77 +
1.78 + /**
1.79 + * Initialization flag to permit calls to setSeed to succeed only
1.80 + * while executing the Random constructor. We can't allow others
1.81 + * since it would cause setting seed in one part of a program to
1.82 + * unintentionally impact other usages by the thread.
1.83 + */
1.84 + boolean initialized;
1.85 +
1.86 + // Padding to help avoid memory contention among seed updates in
1.87 + // different TLRs in the common case that they are located near
1.88 + // each other.
1.89 + private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
1.90 +
1.91 + /**
1.92 + * The actual ThreadLocal
1.93 + */
1.94 + private static final ThreadLocal<ThreadLocalRandom> localRandom =
1.95 + new ThreadLocal<ThreadLocalRandom>() {
1.96 + protected ThreadLocalRandom initialValue() {
1.97 + return new ThreadLocalRandom();
1.98 + }
1.99 + };
1.100 +
1.101 +
1.102 + /**
1.103 + * Constructor called only by localRandom.initialValue.
1.104 + */
1.105 + ThreadLocalRandom() {
1.106 + super();
1.107 + initialized = true;
1.108 + }
1.109 +
1.110 + /**
1.111 + * Returns the current thread's {@code ThreadLocalRandom}.
1.112 + *
1.113 + * @return the current thread's {@code ThreadLocalRandom}
1.114 + */
1.115 + public static ThreadLocalRandom current() {
1.116 + return localRandom.get();
1.117 + }
1.118 +
1.119 + /**
1.120 + * Throws {@code UnsupportedOperationException}. Setting seeds in
1.121 + * this generator is not supported.
1.122 + *
1.123 + * @throws UnsupportedOperationException always
1.124 + */
1.125 + public void setSeed(long seed) {
1.126 + if (initialized)
1.127 + throw new UnsupportedOperationException();
1.128 + rnd = (seed ^ multiplier) & mask;
1.129 + }
1.130 +
1.131 + protected int next(int bits) {
1.132 + rnd = (rnd * multiplier + addend) & mask;
1.133 + return (int) (rnd >>> (48-bits));
1.134 + }
1.135 +
1.136 + /**
1.137 + * Returns a pseudorandom, uniformly distributed value between the
1.138 + * given least value (inclusive) and bound (exclusive).
1.139 + *
1.140 + * @param least the least value returned
1.141 + * @param bound the upper bound (exclusive)
1.142 + * @throws IllegalArgumentException if least greater than or equal
1.143 + * to bound
1.144 + * @return the next value
1.145 + */
1.146 + public int nextInt(int least, int bound) {
1.147 + if (least >= bound)
1.148 + throw new IllegalArgumentException();
1.149 + return nextInt(bound - least) + least;
1.150 + }
1.151 +
1.152 + /**
1.153 + * Returns a pseudorandom, uniformly distributed value
1.154 + * between 0 (inclusive) and the specified value (exclusive).
1.155 + *
1.156 + * @param n the bound on the random number to be returned. Must be
1.157 + * positive.
1.158 + * @return the next value
1.159 + * @throws IllegalArgumentException if n is not positive
1.160 + */
1.161 + public long nextLong(long n) {
1.162 + if (n <= 0)
1.163 + throw new IllegalArgumentException("n must be positive");
1.164 + // Divide n by two until small enough for nextInt. On each
1.165 + // iteration (at most 31 of them but usually much less),
1.166 + // randomly choose both whether to include high bit in result
1.167 + // (offset) and whether to continue with the lower vs upper
1.168 + // half (which makes a difference only if odd).
1.169 + long offset = 0;
1.170 + while (n >= Integer.MAX_VALUE) {
1.171 + int bits = next(2);
1.172 + long half = n >>> 1;
1.173 + long nextn = ((bits & 2) == 0) ? half : n - half;
1.174 + if ((bits & 1) == 0)
1.175 + offset += n - nextn;
1.176 + n = nextn;
1.177 + }
1.178 + return offset + nextInt((int) n);
1.179 + }
1.180 +
1.181 + /**
1.182 + * Returns a pseudorandom, uniformly distributed value between the
1.183 + * given least value (inclusive) and bound (exclusive).
1.184 + *
1.185 + * @param least the least value returned
1.186 + * @param bound the upper bound (exclusive)
1.187 + * @return the next value
1.188 + * @throws IllegalArgumentException if least greater than or equal
1.189 + * to bound
1.190 + */
1.191 + public long nextLong(long least, long bound) {
1.192 + if (least >= bound)
1.193 + throw new IllegalArgumentException();
1.194 + return nextLong(bound - least) + least;
1.195 + }
1.196 +
1.197 + /**
1.198 + * Returns a pseudorandom, uniformly distributed {@code double} value
1.199 + * between 0 (inclusive) and the specified value (exclusive).
1.200 + *
1.201 + * @param n the bound on the random number to be returned. Must be
1.202 + * positive.
1.203 + * @return the next value
1.204 + * @throws IllegalArgumentException if n is not positive
1.205 + */
1.206 + public double nextDouble(double n) {
1.207 + if (n <= 0)
1.208 + throw new IllegalArgumentException("n must be positive");
1.209 + return nextDouble() * n;
1.210 + }
1.211 +
1.212 + /**
1.213 + * Returns a pseudorandom, uniformly distributed value between the
1.214 + * given least value (inclusive) and bound (exclusive).
1.215 + *
1.216 + * @param least the least value returned
1.217 + * @param bound the upper bound (exclusive)
1.218 + * @return the next value
1.219 + * @throws IllegalArgumentException if least greater than or equal
1.220 + * to bound
1.221 + */
1.222 + public double nextDouble(double least, double bound) {
1.223 + if (least >= bound)
1.224 + throw new IllegalArgumentException();
1.225 + return nextDouble() * (bound - least) + least;
1.226 + }
1.227 +
1.228 + private static final long serialVersionUID = -5851777807851030925L;
1.229 +}