1011 lines
40 KiB
Java
1011 lines
40 KiB
Java
/*
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* Copyright (c) 1995, 2021, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util;
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import android.compat.Compatibility;
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import android.compat.annotation.ChangeId;
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import android.compat.annotation.EnabledSince;
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import java.io.*;
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import java.util.concurrent.atomic.AtomicLong;
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import java.util.random.RandomGenerator;
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import java.util.stream.DoubleStream;
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import java.util.stream.IntStream;
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import java.util.stream.LongStream;
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import jdk.internal.util.random.RandomSupport;
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import dalvik.annotation.compat.VersionCodes;
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import dalvik.system.VMRuntime;
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import static jdk.internal.util.random.RandomSupport.*;
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import jdk.internal.misc.Unsafe;
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/**
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* An instance of this class is used to generate a stream of
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* pseudorandom numbers; its period is only 2<sup>48</sup>.
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* The class uses a 48-bit seed, which is
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* modified using a linear congruential formula. (See Donald E. Knuth,
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* <cite>The Art of Computer Programming, Volume 2, Third
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* edition: Seminumerical Algorithms</cite>, Section 3.2.1.)
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* <p>
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* If two instances of {@code Random} are created with the same
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* seed, and the same sequence of method calls is made for each, they
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* will generate and return identical sequences of numbers. In order to
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* guarantee this property, particular algorithms are specified for the
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* class {@code Random}. Java implementations must use all the algorithms
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* shown here for the class {@code Random}, for the sake of absolute
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* portability of Java code. However, subclasses of class {@code Random}
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* are permitted to use other algorithms, so long as they adhere to the
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* general contracts for all the methods.
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* <p>
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* The algorithms implemented by class {@code Random} use a
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* {@code protected} utility method that on each invocation can supply
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* up to 32 pseudorandomly generated bits.
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* <p>
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* Many applications will find the method {@link Math#random} simpler to use.
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*
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* <p>Instances of {@code java.util.Random} are threadsafe.
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* However, the concurrent use of the same {@code java.util.Random}
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* instance across threads may encounter contention and consequent
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* poor performance. Consider instead using
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* {@link java.util.concurrent.ThreadLocalRandom} in multithreaded
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* designs.
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*
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* <p>Instances of {@code java.util.Random} are not cryptographically
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* secure. Consider instead using {@link java.security.SecureRandom} to
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* get a cryptographically secure pseudo-random number generator for use
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* by security-sensitive applications.
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*
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* @author Frank Yellin
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* @since 1.0
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*/
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@SuppressWarnings("exports")
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@RandomGeneratorProperties(
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name = "Random",
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i = 48, j = 0, k = 0,
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equidistribution = 0
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)
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public class Random implements RandomGenerator, java.io.Serializable {
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/** use serialVersionUID from JDK 1.1 for interoperability */
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@java.io.Serial
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static final long serialVersionUID = 3905348978240129619L;
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/**
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* The internal state associated with this pseudorandom number generator.
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* (The specs for the methods in this class describe the ongoing
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* computation of this value.)
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*/
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private final AtomicLong seed;
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private static final long multiplier = 0x5DEECE66DL;
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private static final long addend = 0xBL;
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private static final long mask = (1L << 48) - 1;
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private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
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// Android-added: flag to keep old behaviour of Random.ints().
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/**
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* After https://bugs.openjdk.org/browse/JDK-8301574 ints()
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* and long() methods generate different sequence of number
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* than nextInt() and nextLong() calls would.
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*
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* @hide
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*/
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@ChangeId
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@EnabledSince(targetSdkVersion = VersionCodes.VANILLA_ICE_CREAM)
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public static final long STREAM_INT_DIFFERS_FROM_NEXT_INT = 308103782L;
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/**
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* Creates a new random number generator. This constructor sets
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* the seed of the random number generator to a value very likely
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* to be distinct from any other invocation of this constructor.
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*/
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public Random() {
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this(seedUniquifier() ^ System.nanoTime());
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}
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private static long seedUniquifier() {
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// L'Ecuyer, "Tables of Linear Congruential Generators of
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// Different Sizes and Good Lattice Structure", 1999
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for (;;) {
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long current = seedUniquifier.get();
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long next = current * 1181783497276652981L;
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if (seedUniquifier.compareAndSet(current, next))
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return next;
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}
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}
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private static final AtomicLong seedUniquifier
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= new AtomicLong(8682522807148012L);
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/**
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* Creates a new random number generator using a single {@code long} seed.
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* The seed is the initial value of the internal state of the pseudorandom
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* number generator which is maintained by method {@link #next}.
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*
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* @implSpec The invocation {@code new Random(seed)} is equivalent to:
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* <pre>{@code
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* Random rnd = new Random();
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* rnd.setSeed(seed);
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* }</pre>
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*
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* @param seed the initial seed
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* @see #setSeed(long)
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*/
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public Random(long seed) {
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if (getClass() == Random.class)
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this.seed = new AtomicLong(initialScramble(seed));
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else {
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// subclass might have overridden setSeed
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this.seed = new AtomicLong();
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setSeed(seed);
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}
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}
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private static long initialScramble(long seed) {
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return (seed ^ multiplier) & mask;
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}
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/**
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* Sets the seed of this random number generator using a single
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* {@code long} seed. The general contract of {@code setSeed} is
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* that it alters the state of this random number generator object
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* so as to be in exactly the same state as if it had just been
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* created with the argument {@code seed} as a seed. The method
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* {@code setSeed} is implemented by class {@code Random} by
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* atomically updating the seed to
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* <pre>{@code (seed ^ 0x5DEECE66DL) & ((1L << 48) - 1)}</pre>
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* and clearing the {@code haveNextNextGaussian} flag used by {@link
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* #nextGaussian}.
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*
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* <p>The implementation of {@code setSeed} by class {@code Random}
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* happens to use only 48 bits of the given seed. In general, however,
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* an overriding method may use all 64 bits of the {@code long}
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* argument as a seed value.
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*
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* @param seed the initial seed
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*/
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public synchronized void setSeed(long seed) {
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this.seed.set(initialScramble(seed));
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haveNextNextGaussian = false;
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}
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/**
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* Generates the next pseudorandom number. Subclasses should
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* override this, as this is used by all other methods.
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*
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* <p>The general contract of {@code next} is that it returns an
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* {@code int} value and if the argument {@code bits} is between
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* {@code 1} and {@code 32} (inclusive), then that many low-order
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* bits of the returned value will be (approximately) independently
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* chosen bit values, each of which is (approximately) equally
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* likely to be {@code 0} or {@code 1}. The method {@code next} is
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* implemented by class {@code Random} by atomically updating the seed to
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* <pre>{@code (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)}</pre>
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* and returning
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* <pre>{@code (int)(seed >>> (48 - bits))}.</pre>
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*
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* This is a linear congruential pseudorandom number generator, as
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* defined by D. H. Lehmer and described by Donald E. Knuth in
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* <cite>The Art of Computer Programming, Volume 2, Third edition:
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* Seminumerical Algorithms</cite>, section 3.2.1.
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*
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* @param bits random bits
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* @return the next pseudorandom value from this random number
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* generator's sequence
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* @since 1.1
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*/
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protected int next(int bits) {
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long oldseed, nextseed;
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AtomicLong seed = this.seed;
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do {
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oldseed = seed.get();
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nextseed = (oldseed * multiplier + addend) & mask;
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} while (!seed.compareAndSet(oldseed, nextseed));
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return (int)(nextseed >>> (48 - bits));
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}
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/**
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* Generates random bytes and places them into a user-supplied
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* byte array. The number of random bytes produced is equal to
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* the length of the byte array.
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*
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* @implSpec The method {@code nextBytes} is
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* implemented by class {@code Random} as if by:
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* <pre>{@code
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* public void nextBytes(byte[] bytes) {
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* for (int i = 0; i < bytes.length; )
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* for (int rnd = nextInt(), n = Math.min(bytes.length - i, 4);
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* n-- > 0; rnd >>= 8)
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* bytes[i++] = (byte)rnd;
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* }}</pre>
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*
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* @param bytes the byte array to fill with random bytes
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* @throws NullPointerException if the byte array is null
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* @since 1.1
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*/
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@Override
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public void nextBytes(byte[] bytes) {
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for (int i = 0, len = bytes.length; i < len; )
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for (int rnd = nextInt(),
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n = Math.min(len - i, Integer.SIZE/Byte.SIZE);
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n-- > 0; rnd >>= Byte.SIZE)
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bytes[i++] = (byte)rnd;
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}
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/**
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* Returns the next pseudorandom, uniformly distributed {@code int}
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* value from this random number generator's sequence. The general
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* contract of {@code nextInt} is that one {@code int} value is
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* pseudorandomly generated and returned. All 2<sup>32</sup> possible
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* {@code int} values are produced with (approximately) equal probability.
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*
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* @implSpec The method {@code nextInt} is
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* implemented by class {@code Random} as if by:
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* <pre>{@code
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* public int nextInt() {
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* return next(32);
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* }}</pre>
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*
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* @return the next pseudorandom, uniformly distributed {@code int}
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* value from this random number generator's sequence
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*/
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@Override
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public int nextInt() {
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return next(32);
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}
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/**
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* Returns a pseudorandom, uniformly distributed {@code int} value
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* between 0 (inclusive) and the specified value (exclusive), drawn from
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* this random number generator's sequence. The general contract of
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* {@code nextInt} is that one {@code int} value in the specified range
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* is pseudorandomly generated and returned. All {@code bound} possible
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* {@code int} values are produced with (approximately) equal
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* probability.
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*
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* @implSpec The method {@code nextInt(int bound)} is implemented by
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* class {@code Random} as if by:
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* <pre>{@code
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* public int nextInt(int bound) {
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* if (bound <= 0)
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* throw new IllegalArgumentException("bound must be positive");
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*
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* if ((bound & -bound) == bound) // i.e., bound is a power of 2
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* return (int)((bound * (long)next(31)) >> 31);
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*
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* int bits, val;
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* do {
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* bits = next(31);
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* val = bits % bound;
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* } while (bits - val + (bound-1) < 0);
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* return val;
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* }}</pre>
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*
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* <p>The hedge "approximately" is used in the foregoing description only
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* because the next method is only approximately an unbiased source of
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* independently chosen bits. If it were a perfect source of randomly
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* chosen bits, then the algorithm shown would choose {@code int}
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* values from the stated range with perfect uniformity.
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* <p>
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* The algorithm is slightly tricky. It rejects values that would result
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* in an uneven distribution (due to the fact that 2^31 is not divisible
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* by n). The probability of a value being rejected depends on n. The
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* worst case is n=2^30+1, for which the probability of a reject is 1/2,
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* and the expected number of iterations before the loop terminates is 2.
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* <p>
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* The algorithm treats the case where n is a power of two specially: it
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* returns the correct number of high-order bits from the underlying
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* pseudo-random number generator. In the absence of special treatment,
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* the correct number of <i>low-order</i> bits would be returned. Linear
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* congruential pseudo-random number generators such as the one
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* implemented by this class are known to have short periods in the
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* sequence of values of their low-order bits. Thus, this special case
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* greatly increases the length of the sequence of values returned by
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* successive calls to this method if n is a small power of two.
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*
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* @param bound the upper bound (exclusive). Must be positive.
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* @return the next pseudorandom, uniformly distributed {@code int}
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* value between zero (inclusive) and {@code bound} (exclusive)
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* from this random number generator's sequence
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* @throws IllegalArgumentException if bound is not positive
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* @since 1.2
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*/
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@Override
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public int nextInt(int bound) {
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if (bound <= 0)
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throw new IllegalArgumentException(BAD_BOUND);
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int r = next(31);
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int m = bound - 1;
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if ((bound & m) == 0) // i.e., bound is a power of 2
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r = (int)((bound * (long)r) >> 31);
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else { // reject over-represented candidates
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for (int u = r;
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u - (r = u % bound) + m < 0;
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u = next(31))
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;
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}
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return r;
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}
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/**
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* Returns the next pseudorandom, uniformly distributed {@code long}
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* value from this random number generator's sequence. The general
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* contract of {@code nextLong} is that one {@code long} value is
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* pseudorandomly generated and returned.
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*
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* @implSpec The method {@code nextLong} is implemented by class {@code Random}
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* as if by:
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* <pre>{@code
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* public long nextLong() {
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* return ((long)next(32) << 32) + next(32);
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* }}</pre>
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*
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* Because class {@code Random} uses a seed with only 48 bits,
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* this algorithm will not return all possible {@code long} values.
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*
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* @return the next pseudorandom, uniformly distributed {@code long}
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* value from this random number generator's sequence
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*/
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@Override
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public long nextLong() {
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// it's okay that the bottom word remains signed.
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return ((long)(next(32)) << 32) + next(32);
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}
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/**
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* Returns the next pseudorandom, uniformly distributed
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* {@code boolean} value from this random number generator's
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* sequence. The general contract of {@code nextBoolean} is that one
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* {@code boolean} value is pseudorandomly generated and returned. The
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* values {@code true} and {@code false} are produced with
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* (approximately) equal probability.
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*
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* @implSpec The method {@code nextBoolean} is implemented by class
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* {@code Random} as if by:
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* <pre>{@code
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* public boolean nextBoolean() {
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* return next(1) != 0;
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* }}</pre>
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*
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* @return the next pseudorandom, uniformly distributed
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* {@code boolean} value from this random number generator's
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* sequence
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* @since 1.2
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*/
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@Override
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public boolean nextBoolean() {
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return next(1) != 0;
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}
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/**
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* Returns the next pseudorandom, uniformly distributed {@code float}
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* value between {@code 0.0} and {@code 1.0} from this random
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* number generator's sequence.
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*
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* <p>The general contract of {@code nextFloat} is that one
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* {@code float} value, chosen (approximately) uniformly from the
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* range {@code 0.0f} (inclusive) to {@code 1.0f} (exclusive), is
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* pseudorandomly generated and returned. All 2<sup>24</sup> possible
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* {@code float} values of the form <i>m x </i>2<sup>-24</sup>,
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* where <i>m</i> is a positive integer less than 2<sup>24</sup>, are
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* produced with (approximately) equal probability.
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*
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* @implSpec The method {@code nextFloat} is implemented by class
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* {@code Random} as if by:
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* <pre>{@code
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* public float nextFloat() {
|
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* return next(24) / ((float)(1 << 24));
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* }}</pre>
|
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* <p>The hedge "approximately" is used in the foregoing description only
|
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* because the next method is only approximately an unbiased source of
|
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* independently chosen bits. If it were a perfect source of randomly
|
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* chosen bits, then the algorithm shown would choose {@code float}
|
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* values from the stated range with perfect uniformity.<p>
|
|
* [In early versions of Java, the result was incorrectly calculated as:
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* <pre> {@code return next(30) / ((float)(1 << 30));}</pre>
|
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* This might seem to be equivalent, if not better, but in fact it
|
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* introduced a slight nonuniformity because of the bias in the rounding
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|
* of floating-point numbers: it was slightly more likely that the
|
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* low-order bit of the significand would be 0 than that it would be 1.]
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*
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* @return the next pseudorandom, uniformly distributed {@code float}
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* value between {@code 0.0} and {@code 1.0} from this
|
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* random number generator's sequence
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*/
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@Override
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public float nextFloat() {
|
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return next(24) / ((float)(1 << 24));
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}
|
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|
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/**
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* Returns the next pseudorandom, uniformly distributed
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* {@code double} value between {@code 0.0} and
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* {@code 1.0} from this random number generator's sequence.
|
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*
|
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* <p>The general contract of {@code nextDouble} is that one
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* {@code double} value, chosen (approximately) uniformly from the
|
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* range {@code 0.0d} (inclusive) to {@code 1.0d} (exclusive), is
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* pseudorandomly generated and returned.
|
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*
|
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* @implSpec The method {@code nextDouble} is implemented by class
|
|
* {@code Random} as if by:
|
|
* <pre>{@code
|
|
* public double nextDouble() {
|
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* return (((long)next(26) << 27) + next(27))
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* / (double)(1L << 53);
|
|
* }}</pre>
|
|
* <p>The hedge "approximately" is used in the foregoing description only
|
|
* because the {@code next} method is only approximately an unbiased source
|
|
* of independently chosen bits. If it were a perfect source of randomly
|
|
* chosen bits, then the algorithm shown would choose {@code double} values
|
|
* from the stated range with perfect uniformity.
|
|
* <p>[In early versions of Java, the result was incorrectly calculated as:
|
|
* <pre> {@code return (((long)next(27) << 27) + next(27)) / (double)(1L << 54);}</pre>
|
|
* This might seem to be equivalent, if not better, but in fact it
|
|
* introduced a large nonuniformity because of the bias in the rounding of
|
|
* floating-point numbers: it was three times as likely that the low-order
|
|
* bit of the significand would be 0 than that it would be 1! This
|
|
* nonuniformity probably doesn't matter much in practice, but we strive
|
|
* for perfection.]
|
|
*
|
|
* @return the next pseudorandom, uniformly distributed {@code double}
|
|
* value between {@code 0.0} and {@code 1.0} from this
|
|
* random number generator's sequence
|
|
* @see Math#random
|
|
*/
|
|
@Override
|
|
public double nextDouble() {
|
|
return (((long)(next(26)) << 27) + next(27)) * DOUBLE_UNIT;
|
|
}
|
|
|
|
private double nextNextGaussian;
|
|
private boolean haveNextNextGaussian = false;
|
|
|
|
/**
|
|
* Returns the next pseudorandom, Gaussian ("normally") distributed
|
|
* {@code double} value with mean {@code 0.0} and standard
|
|
* deviation {@code 1.0} from this random number generator's sequence.
|
|
* <p>
|
|
* The general contract of {@code nextGaussian} is that one
|
|
* {@code double} value, chosen from (approximately) the usual
|
|
* normal distribution with mean {@code 0.0} and standard deviation
|
|
* {@code 1.0}, is pseudorandomly generated and returned.
|
|
*
|
|
* @implSpec The method {@code nextGaussian} is implemented by class
|
|
* {@code Random} as if by a threadsafe version of the following:
|
|
* <pre>{@code
|
|
* private double nextNextGaussian;
|
|
* private boolean haveNextNextGaussian = false;
|
|
*
|
|
* public double nextGaussian() {
|
|
* if (haveNextNextGaussian) {
|
|
* haveNextNextGaussian = false;
|
|
* return nextNextGaussian;
|
|
* } else {
|
|
* double v1, v2, s;
|
|
* do {
|
|
* v1 = 2 * nextDouble() - 1; // between -1.0 and 1.0
|
|
* v2 = 2 * nextDouble() - 1; // between -1.0 and 1.0
|
|
* s = v1 * v1 + v2 * v2;
|
|
* } while (s >= 1 || s == 0);
|
|
* double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
|
|
* nextNextGaussian = v2 * multiplier;
|
|
* haveNextNextGaussian = true;
|
|
* return v1 * multiplier;
|
|
* }
|
|
* }}</pre>
|
|
*
|
|
* This uses the <i>polar method</i> of G. E. P. Box, M. E. Muller, and
|
|
* G. Marsaglia, as described by Donald E. Knuth in <cite>The Art of
|
|
* Computer Programming, Volume 2, third edition: Seminumerical Algorithms</cite>,
|
|
* section 3.4.1, subsection C, algorithm P. Note that it generates two
|
|
* independent values at the cost of only one call to {@code StrictMath.log}
|
|
* and one call to {@code StrictMath.sqrt}.
|
|
*
|
|
* @return the next pseudorandom, Gaussian ("normally") distributed
|
|
* {@code double} value with mean {@code 0.0} and
|
|
* standard deviation {@code 1.0} from this random number
|
|
* generator's sequence
|
|
*/
|
|
@Override
|
|
public synchronized double nextGaussian() {
|
|
// See Knuth, TAOCP, Vol. 2, 3rd edition, Section 3.4.1 Algorithm C.
|
|
if (haveNextNextGaussian) {
|
|
haveNextNextGaussian = false;
|
|
return nextNextGaussian;
|
|
} else {
|
|
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);
|
|
nextNextGaussian = v2 * multiplier;
|
|
haveNextNextGaussian = true;
|
|
return v1 * multiplier;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Serializable fields for Random.
|
|
*
|
|
* @serialField seed long
|
|
* seed for random computations
|
|
* @serialField nextNextGaussian double
|
|
* next Gaussian to be returned
|
|
* @serialField haveNextNextGaussian boolean
|
|
* nextNextGaussian is valid
|
|
*/
|
|
@java.io.Serial
|
|
private static final ObjectStreamField[] serialPersistentFields = {
|
|
new ObjectStreamField("seed", Long.TYPE),
|
|
new ObjectStreamField("nextNextGaussian", Double.TYPE),
|
|
new ObjectStreamField("haveNextNextGaussian", Boolean.TYPE)
|
|
};
|
|
|
|
/**
|
|
* Reconstitute the {@code Random} instance from a stream (that is,
|
|
* deserialize it).
|
|
*
|
|
* @param s the {@code ObjectInputStream} from which data is read
|
|
*
|
|
* @throws IOException if an I/O error occurs
|
|
* @throws ClassNotFoundException if a serialized class cannot be loaded
|
|
*/
|
|
@java.io.Serial
|
|
private void readObject(java.io.ObjectInputStream s)
|
|
throws java.io.IOException, ClassNotFoundException {
|
|
|
|
ObjectInputStream.GetField fields = s.readFields();
|
|
|
|
// The seed is read in as {@code long} for
|
|
// historical reasons, but it is converted to an AtomicLong.
|
|
long seedVal = fields.get("seed", -1L);
|
|
if (seedVal < 0)
|
|
throw new java.io.StreamCorruptedException(
|
|
"Random: invalid seed");
|
|
resetSeed(seedVal);
|
|
nextNextGaussian = fields.get("nextNextGaussian", 0.0);
|
|
haveNextNextGaussian = fields.get("haveNextNextGaussian", false);
|
|
}
|
|
|
|
/**
|
|
* Save the {@code Random} instance to a stream.
|
|
*
|
|
* @param s the {@code ObjectOutputStream} to which data is written
|
|
*
|
|
* @throws IOException if an I/O error occurs
|
|
*/
|
|
@java.io.Serial
|
|
private synchronized void writeObject(ObjectOutputStream s)
|
|
throws IOException {
|
|
|
|
// set the values of the Serializable fields
|
|
ObjectOutputStream.PutField fields = s.putFields();
|
|
|
|
// The seed is serialized as a long for historical reasons.
|
|
fields.put("seed", seed.get());
|
|
fields.put("nextNextGaussian", nextNextGaussian);
|
|
fields.put("haveNextNextGaussian", haveNextNextGaussian);
|
|
|
|
// save them
|
|
s.writeFields();
|
|
}
|
|
|
|
// Support for resetting seed while deserializing
|
|
private static final Unsafe unsafe = Unsafe.getUnsafe();
|
|
private static final long seedOffset;
|
|
static {
|
|
try {
|
|
seedOffset = unsafe.objectFieldOffset
|
|
(Random.class.getDeclaredField("seed"));
|
|
} catch (Exception ex) { throw new Error(ex); }
|
|
}
|
|
private void resetSeed(long seedVal) {
|
|
unsafe.putReferenceVolatile(this, seedOffset, new AtomicLong(seedVal));
|
|
}
|
|
|
|
/**
|
|
* Returns a stream producing the given {@code streamSize} number of
|
|
* pseudorandom {@code int} values.
|
|
*
|
|
* <p>A pseudorandom {@code int} value is generated as if it's the result of
|
|
* calling the method {@link #nextInt()}.
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public IntStream ints(long streamSize) {
|
|
return AbstractSpliteratorGenerator.ints(this, streamSize);
|
|
}
|
|
|
|
/**
|
|
* Returns an effectively unlimited stream of pseudorandom {@code int}
|
|
* values.
|
|
*
|
|
* <p>A pseudorandom {@code int} value is generated as if it's the result of
|
|
* calling the method {@link #nextInt()}.
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public IntStream ints() {
|
|
// Android-changed: keep old behaviour for apps targeting already released
|
|
// platforms.
|
|
// return AbstractSpliteratorGenerator.ints(this);
|
|
if (VMRuntime.getSdkVersion() >= VersionCodes.VANILLA_ICE_CREAM &&
|
|
Compatibility.isChangeEnabled(STREAM_INT_DIFFERS_FROM_NEXT_INT)) {
|
|
return AbstractSpliteratorGenerator.ints(this);
|
|
} else {
|
|
return IntStream.generate(this::nextInt);
|
|
}
|
|
}
|
|
|
|
// Android-added: implementation specified in ints(long, int, int) javadoc.
|
|
private int boundedNextInt(int origin, int bound) {
|
|
int n = bound - origin;
|
|
if (n > 0) {
|
|
return nextInt(n) + origin;
|
|
} else { // range not representable as int
|
|
int r;
|
|
do {
|
|
r = nextInt();
|
|
} while (r < origin || r >= bound);
|
|
return r;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns a stream producing the given {@code streamSize} number
|
|
* of pseudorandom {@code int} values, each conforming to the given
|
|
* origin (inclusive) and bound (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code int} value is generated as if it's the result of
|
|
* calling the following method with the origin and bound:
|
|
* <pre> {@code
|
|
* int nextInt(int origin, int bound) {
|
|
* int n = bound - origin;
|
|
* if (n > 0) {
|
|
* return nextInt(n) + origin;
|
|
* }
|
|
* else { // range not representable as int
|
|
* int r;
|
|
* do {
|
|
* r = nextInt();
|
|
* } while (r < origin || r >= bound);
|
|
* return r;
|
|
* }
|
|
* }}</pre>
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound) {
|
|
// Android-changed: keep old behaviour for apps targeting already released
|
|
// platforms.
|
|
// return AbstractSpliteratorGenerator.ints(this, streamSize, randomNumberOrigin, randomNumberBound);
|
|
if (VMRuntime.getSdkVersion() >= VersionCodes.VANILLA_ICE_CREAM &&
|
|
Compatibility.isChangeEnabled(STREAM_INT_DIFFERS_FROM_NEXT_INT)) {
|
|
return AbstractSpliteratorGenerator.ints(this, streamSize, randomNumberOrigin, randomNumberBound);
|
|
} else {
|
|
RandomSupport.checkStreamSize(streamSize);
|
|
RandomSupport.checkRange(randomNumberOrigin, randomNumberBound);
|
|
return IntStream
|
|
.generate(() -> boundedNextInt(randomNumberOrigin, randomNumberBound))
|
|
.limit(streamSize);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns an effectively unlimited stream of pseudorandom {@code
|
|
* int} values, each conforming to the given origin (inclusive) and bound
|
|
* (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code int} value is generated as if it's the result of
|
|
* calling the following method with the origin and bound:
|
|
* <pre> {@code
|
|
* int nextInt(int origin, int bound) {
|
|
* int n = bound - origin;
|
|
* if (n > 0) {
|
|
* return nextInt(n) + origin;
|
|
* }
|
|
* else { // range not representable as int
|
|
* int r;
|
|
* do {
|
|
* r = nextInt();
|
|
* } while (r < origin || r >= bound);
|
|
* return r;
|
|
* }
|
|
* }}</pre>
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
|
|
// Android-changed: keep old behaviour for apps targeting already released
|
|
// platforms.
|
|
// return AbstractSpliteratorGenerator.ints(this, randomNumberOrigin, randomNumberBound);
|
|
if (VMRuntime.getSdkVersion() >= VersionCodes.VANILLA_ICE_CREAM &&
|
|
Compatibility.isChangeEnabled(STREAM_INT_DIFFERS_FROM_NEXT_INT)) {
|
|
return AbstractSpliteratorGenerator.ints(this, randomNumberOrigin, randomNumberBound);
|
|
} else {
|
|
RandomSupport.checkRange(randomNumberOrigin, randomNumberBound);
|
|
return IntStream.generate(() -> boundedNextInt(randomNumberOrigin, randomNumberBound));
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns a stream producing the given {@code streamSize} number of
|
|
* pseudorandom {@code long} values.
|
|
*
|
|
* <p>A pseudorandom {@code long} value is generated as if it's the result
|
|
* of calling the method {@link #nextLong()}.
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public LongStream longs(long streamSize) {
|
|
return AbstractSpliteratorGenerator.longs(this, streamSize);
|
|
}
|
|
|
|
/**
|
|
* Returns an effectively unlimited stream of pseudorandom {@code long}
|
|
* values.
|
|
*
|
|
* <p>A pseudorandom {@code long} value is generated as if it's the result
|
|
* of calling the method {@link #nextLong()}.
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public LongStream longs() {
|
|
return AbstractSpliteratorGenerator.longs(this);
|
|
}
|
|
|
|
/**
|
|
* Returns a stream producing the given {@code streamSize} number of
|
|
* pseudorandom {@code long}, each conforming to the given origin
|
|
* (inclusive) and bound (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code long} value is generated as if it's the result
|
|
* of calling the following method with the origin and bound:
|
|
* <pre> {@code
|
|
* long nextLong(long origin, long bound) {
|
|
* long r = nextLong();
|
|
* 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 = nextLong() >>> 1) // retry
|
|
* ;
|
|
* r += origin;
|
|
* }
|
|
* else { // range not representable as long
|
|
* while (r < origin || r >= bound)
|
|
* r = nextLong();
|
|
* }
|
|
* return r;
|
|
* }}</pre>
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound) {
|
|
return AbstractSpliteratorGenerator.longs(this, streamSize, randomNumberOrigin, randomNumberBound);
|
|
}
|
|
|
|
/**
|
|
* Returns an effectively unlimited stream of pseudorandom {@code
|
|
* long} values, each conforming to the given origin (inclusive) and bound
|
|
* (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code long} value is generated as if it's the result
|
|
* of calling the following method with the origin and bound:
|
|
* <pre> {@code
|
|
* long nextLong(long origin, long bound) {
|
|
* long r = nextLong();
|
|
* 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 = nextLong() >>> 1) // retry
|
|
* ;
|
|
* r += origin;
|
|
* }
|
|
* else { // range not representable as long
|
|
* while (r < origin || r >= bound)
|
|
* r = nextLong();
|
|
* }
|
|
* return r;
|
|
* }}</pre>
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
|
|
return AbstractSpliteratorGenerator.longs(this, randomNumberOrigin, randomNumberBound);
|
|
}
|
|
|
|
/**
|
|
* Returns a stream producing the given {@code streamSize} number of
|
|
* pseudorandom {@code double} values, each between zero
|
|
* (inclusive) and one (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code double} value is generated as if it's the result
|
|
* of calling the method {@link #nextDouble()}.
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public DoubleStream doubles(long streamSize) {
|
|
return AbstractSpliteratorGenerator.doubles(this, streamSize);
|
|
}
|
|
|
|
/**
|
|
* Returns an effectively unlimited stream of pseudorandom {@code
|
|
* double} values, each between zero (inclusive) and one
|
|
* (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code double} value is generated as if it's the result
|
|
* of calling the method {@link #nextDouble()}.
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public DoubleStream doubles() {
|
|
return AbstractSpliteratorGenerator.doubles(this);
|
|
}
|
|
|
|
/**
|
|
* Returns a stream producing the given {@code streamSize} number of
|
|
* pseudorandom {@code double} values, each conforming to the given origin
|
|
* (inclusive) and bound (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code double} value is generated as if it's the result
|
|
* of calling the following method with the origin and bound:
|
|
* <pre> {@code
|
|
* double nextDouble(double origin, double bound) {
|
|
* double r = nextDouble();
|
|
* r = r * (bound - origin) + origin;
|
|
* if (r >= bound) // correct for rounding
|
|
* r = Math.nextDown(bound);
|
|
* return r;
|
|
* }}</pre>
|
|
*
|
|
* @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,
|
|
* or {@code randomNumberOrigin} is not finite,
|
|
* or {@code randomNumberBound} is not finite, or {@code randomNumberOrigin}
|
|
* is greater than or equal to {@code randomNumberBound}
|
|
* @since 1.8
|
|
*/
|
|
@Override
|
|
public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound) {
|
|
return AbstractSpliteratorGenerator.doubles(this, streamSize, randomNumberOrigin, randomNumberBound);
|
|
}
|
|
|
|
/**
|
|
* Returns an effectively unlimited stream of pseudorandom {@code
|
|
* double} values, each conforming to the given origin (inclusive) and bound
|
|
* (exclusive).
|
|
*
|
|
* <p>A pseudorandom {@code double} value is generated as if it's the result
|
|
* of calling the following method with the origin and bound:
|
|
* <pre> {@code
|
|
* double nextDouble(double origin, double bound) {
|
|
* double r = nextDouble();
|
|
* r = r * (bound - origin) + origin;
|
|
* if (r >= bound) // correct for rounding
|
|
* r = Math.nextDown(bound);
|
|
* return r;
|
|
* }}</pre>
|
|
*
|
|
* @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
|
|
*/
|
|
@Override
|
|
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
|
|
return AbstractSpliteratorGenerator.doubles(this, randomNumberOrigin, randomNumberBound);
|
|
}
|
|
}
|