| /* | |
| * Copyright (c) 1995, 2024, Oracle and/or its affiliates. All rights reserved. | |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| * | |
| * This code is free software; you can redistribute it and/or modify it | |
| * under the terms of the GNU General Public License version 2 only, as | |
| * published by the Free Software Foundation. Oracle designates this | |
| * particular file as subject to the "Classpath" exception as provided | |
| * by Oracle in the LICENSE file that accompanied this code. | |
| * | |
| * This code is distributed in the hope that it will be useful, but WITHOUT | |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| * version 2 for more details (a copy is included in the LICENSE file that | |
| * accompanied this code). | |
| * | |
| * You should have received a copy of the GNU General Public License version | |
| * 2 along with this work; if not, write to the Free Software Foundation, | |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| * | |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| * or visit www.oracle.com if you need additional information or have any | |
| * questions. | |
| */ | |
| package java.util; | |
| import java.io.*; | |
| import java.util.concurrent.atomic.AtomicLong; | |
| import java.util.random.RandomGenerator; | |
| import java.util.stream.DoubleStream; | |
| import java.util.stream.IntStream; | |
| import java.util.stream.LongStream; | |
| import static jdk.internal.util.random.RandomSupport.*; | |
| import jdk.internal.misc.Unsafe; | |
| /** | |
| * An instance of this class is used to generate a stream of | |
| * pseudorandom numbers; its period is only 2<sup>48</sup>. | |
| * The class uses a 48-bit seed, which is | |
| * modified using a linear congruential formula. (See Donald E. Knuth, | |
| * <cite>The Art of Computer Programming, Volume 2, Third | |
| * edition: Seminumerical Algorithms</cite>, Section 3.2.1.) | |
| * <p> | |
| * If two instances of {@code Random} are created with the same | |
| * seed, and the same sequence of method calls is made for each, they | |
| * will generate and return identical sequences of numbers. In order to | |
| * guarantee this property, particular algorithms are specified for the | |
| * class {@code Random}. Java implementations must use all the algorithms | |
| * shown here for the class {@code Random}, for the sake of absolute | |
| * portability of Java code. However, subclasses of class {@code Random} | |
| * are permitted to use other algorithms, so long as they adhere to the | |
| * general contracts for all the methods. | |
| * <p> | |
| * The algorithms implemented by class {@code Random} use a | |
| * {@code protected} utility method that on each invocation can supply | |
| * up to 32 pseudorandomly generated bits. | |
| * <p> | |
| * Many applications will find the method {@link Math#random} simpler to use. | |
| * | |
| * <p>Instances of {@code java.util.Random} are threadsafe. | |
| * However, the concurrent use of the same {@code java.util.Random} | |
| * instance across threads may encounter contention and consequent | |
| * poor performance. Consider instead using | |
| * {@link java.util.concurrent.ThreadLocalRandom} in multithreaded | |
| * designs. | |
| * | |
| * <p>Instances of {@code java.util.Random} are not cryptographically | |
| * secure. Consider instead using {@link java.security.SecureRandom} to | |
| * get a cryptographically secure pseudo-random number generator for use | |
| * by security-sensitive applications. | |
| * | |
| * @author Frank Yellin | |
| * @since 1.0 | |
| */ | |
| public class Random implements RandomGenerator, java.io.Serializable { | |
| /** | |
| * Class used to wrap a {@link java.util.random.RandomGenerator} to | |
| * {@link java.util.Random}. | |
| */ | |
| @SuppressWarnings("serial") | |
| private static final class RandomWrapper extends Random implements RandomGenerator { | |
| private final RandomGenerator generator; | |
| //randomToWrap must never be null | |
| private RandomWrapper(RandomGenerator randomToWrap) { | |
| super(null); | |
| this.generator = randomToWrap; | |
| } | |
| /** | |
| * Throws {@code NotSerializableException}. | |
| * | |
| * @param s the object input stream | |
| * @throws NotSerializableException always | |
| */ | |
| @Serial | |
| private void readObject(ObjectInputStream s) throws NotSerializableException { | |
| throw new NotSerializableException("not serializable"); | |
| } | |
| /** | |
| * Throws {@code NotSerializableException}. | |
| * | |
| * @param s the object output stream | |
| * @throws NotSerializableException always | |
| */ | |
| @Serial | |
| private void writeObject(ObjectOutputStream s) throws NotSerializableException { | |
| throw new NotSerializableException("not serializable"); | |
| } | |
| /** | |
| * setSeed does not exist in {@link java.util.random.RandomGenerator} so can't | |
| * use it. | |
| */ | |
| @Override | |
| public void setSeed(long seed) { | |
| throw new UnsupportedOperationException(); | |
| } | |
| @Override | |
| public boolean isDeprecated() { | |
| return generator.isDeprecated(); | |
| } | |
| @Override | |
| public void nextBytes(byte[] bytes) { | |
| this.generator.nextBytes(bytes); | |
| } | |
| @Override | |
| public int nextInt() { | |
| return this.generator.nextInt(); | |
| } | |
| @Override | |
| public int nextInt(int bound) { | |
| return this.generator.nextInt(bound); | |
| } | |
| @Override | |
| public int nextInt(int origin, int bound) { | |
| return generator.nextInt(origin, bound); | |
| } | |
| @Override | |
| public long nextLong() { | |
| return this.generator.nextLong(); | |
| } | |
| @Override | |
| public long nextLong(long bound) { | |
| return generator.nextLong(bound); | |
| } | |
| @Override | |
| public long nextLong(long origin, long bound) { | |
| return generator.nextLong(origin, bound); | |
| } | |
| @Override | |
| public boolean nextBoolean() { | |
| return this.generator.nextBoolean(); | |
| } | |
| @Override | |
| public float nextFloat() { | |
| return this.generator.nextFloat(); | |
| } | |
| @Override | |
| public float nextFloat(float bound) { | |
| return generator.nextFloat(bound); | |
| } | |
| @Override | |
| public float nextFloat(float origin, float bound) { | |
| return generator.nextFloat(origin, bound); | |
| } | |
| @Override | |
| public double nextDouble() { | |
| return this.generator.nextDouble(); | |
| } | |
| @Override | |
| public double nextDouble(double bound) { | |
| return generator.nextDouble(bound); | |
| } | |
| @Override | |
| public double nextDouble(double origin, double bound) { | |
| return generator.nextDouble(origin, bound); | |
| } | |
| @Override | |
| public double nextExponential() { | |
| return generator.nextExponential(); | |
| } | |
| @Override | |
| public double nextGaussian() { | |
| return this.generator.nextGaussian(); | |
| } | |
| @Override | |
| public double nextGaussian(double mean, double stddev) { | |
| return generator.nextGaussian(mean, stddev); | |
| } | |
| @Override | |
| public IntStream ints(long streamSize) { | |
| return this.generator.ints(streamSize); | |
| } | |
| @Override | |
| public IntStream ints() { | |
| return this.generator.ints(); | |
| } | |
| @Override | |
| public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound) { | |
| return this.generator.ints(streamSize, randomNumberOrigin, randomNumberBound); | |
| } | |
| @Override | |
| public IntStream ints(int randomNumberOrigin, int randomNumberBound) { | |
| return this.generator.ints(randomNumberOrigin, randomNumberBound); | |
| } | |
| @Override | |
| public LongStream longs(long streamSize) { | |
| return this.generator.longs(streamSize); | |
| } | |
| @Override | |
| public LongStream longs() { | |
| return this.generator.longs(); | |
| } | |
| @Override | |
| public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound) { | |
| return this.generator.longs(streamSize, randomNumberOrigin, randomNumberBound); | |
| } | |
| @Override | |
| public LongStream longs(long randomNumberOrigin, long randomNumberBound) { | |
| return this.generator.longs(randomNumberOrigin, randomNumberBound); | |
| } | |
| @Override | |
| public DoubleStream doubles(long streamSize) { | |
| return this.generator.doubles(streamSize); | |
| } | |
| @Override | |
| public DoubleStream doubles() { | |
| return this.generator.doubles(); | |
| } | |
| @Override | |
| public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound) { | |
| return this.generator.doubles(streamSize, randomNumberOrigin, randomNumberBound); | |
| } | |
| @Override | |
| public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { | |
| return this.generator.doubles(randomNumberOrigin, randomNumberBound); | |
| } | |
| //This method should never be reached unless done by reflection so we should throw when tried | |
| @Override | |
| protected int next(int bits) { | |
| throw new UnsupportedOperationException(); | |
| } | |
| @Override | |
| public String toString() { | |
| return "RandomWrapper[" + generator + "]"; | |
| } | |
| } | |
| /** use serialVersionUID from JDK 1.1 for interoperability */ | |
| @java.io.Serial | |
| static final long serialVersionUID = 3905348978240129619L; | |
| /** | |
| * The internal state associated with this pseudorandom number generator. | |
| * (The specs for the methods in this class describe the ongoing | |
| * computation of this value.) | |
| */ | |
| private final AtomicLong seed; | |
| private static final long multiplier = 0x5DEECE66DL; | |
| private static final long addend = 0xBL; | |
| private static final long mask = (1L << 48) - 1; | |
| private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << Double.PRECISION) | |
| private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << Float.PRECISION) | |
| /** | |
| * Creates a new random number generator. This constructor sets | |
| * the seed of the random number generator to a value very likely | |
| * to be distinct from any other invocation of this constructor. | |
| */ | |
| public Random() { | |
| this(seedUniquifier() ^ System.nanoTime()); | |
| } | |
| private Random(Void unused) { | |
| this.seed = null; | |
| } | |
| private static long seedUniquifier() { | |
| // L'Ecuyer, "Tables of Linear Congruential Generators of | |
| // Different Sizes and Good Lattice Structure", 1999 | |
| for (;;) { | |
| long current = seedUniquifier.get(); | |
| long next = current * 1181783497276652981L; | |
| if (seedUniquifier.compareAndSet(current, next)) | |
| return next; | |
| } | |
| } | |
| private static final AtomicLong seedUniquifier | |
| = new AtomicLong(8682522807148012L); | |
| /** | |
| * Creates a new random number generator using a single {@code long} seed. | |
| * The seed is the initial value of the internal state of the pseudorandom | |
| * number generator which is maintained by method {@link #next}. | |
| * | |
| * @implSpec The invocation {@code new Random(seed)} is equivalent to: | |
| * <pre>{@code | |
| * Random rnd = new Random(); | |
| * rnd.setSeed(seed); | |
| * }</pre> | |
| * | |
| * @param seed the initial seed | |
| * @see #setSeed(long) | |
| */ | |
| @SuppressWarnings("this-escape") | |
| public Random(long seed) { | |
| if (getClass() == Random.class) | |
| this.seed = new AtomicLong(initialScramble(seed)); | |
| else { | |
| // subclass might have overridden setSeed | |
| this.seed = new AtomicLong(); | |
| setSeed(seed); | |
| } | |
| } | |
| private static long initialScramble(long seed) { | |
| return (seed ^ multiplier) & mask; | |
| } | |
| /** | |
| * Returns an instance of {@code Random} that delegates method calls to the {@link RandomGenerator} | |
| * argument. If the generator is an instance of {@code Random}, it is returned. Otherwise, this method | |
| * returns an instance of {@code Random} that delegates all methods except {@code setSeed} to the generator. | |
| * The returned instance's {@code setSeed} method always throws {@link UnsupportedOperationException}. | |
| * The returned instance is not serializable. | |
| * | |
| * @param generator the {@code RandomGenerator} calls are delegated to | |
| * @return the delegating {@code Random} instance | |
| * @throws NullPointerException if generator is null | |
| * @since 19 | |
| */ | |
| public static Random from(RandomGenerator generator) { | |
| Objects.requireNonNull(generator); | |
| if (generator instanceof Random rand) | |
| return rand; | |
| return new RandomWrapper(generator); | |
| } | |
| /** | |
| * Sets or updates the seed of this random number generator using the | |
| * provided {@code long} seed value (optional operation). | |
| * | |
| * @implSpec | |
| * The implementation in this class alters the state of this random number | |
| * generator so that it is in the same state as if it had just been created with | |
| * {@link #Random(long) new Random(seed)}. It atomically updates the seed to | |
| * <pre>{@code (seed ^ 0x5DEECE66DL) & ((1L << 48) - 1)}</pre> | |
| * and clears the {@code haveNextNextGaussian} flag used by {@link #nextGaussian}. | |
| * Note that this uses only 48 bits of the given seed value. | |
| * | |
| * @param seed the seed value | |
| * @throws UnsupportedOperationException if the {@code setSeed} | |
| * operation is not supported by this random number generator | |
| */ | |
| public synchronized void setSeed(long seed) { | |
| this.seed.set(initialScramble(seed)); | |
| haveNextNextGaussian = false; | |
| } | |
| /** | |
| * Generates the next pseudorandom number. This method returns an | |
| * {@code int} value such that, if the argument {@code bits} is between | |
| * {@code 1} and {@code 32} (inclusive), then that many low-order | |
| * bits of the returned value will be (approximately) independently | |
| * chosen bit values, each of which is (approximately) equally | |
| * likely to be {@code 0} or {@code 1}. | |
| * | |
| * @apiNote | |
| * The other random-producing methods in this class are implemented | |
| * in terms of this method, so subclasses can override just this | |
| * method to provide a different source of pseudorandom numbers for | |
| * the entire class. | |
| * | |
| * @implSpec | |
| * The implementation in this class atomically updates the seed to | |
| * <pre>{@code (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)}</pre> | |
| * and returns | |
| * <pre>{@code (int)(seed >>> (48 - bits))}.</pre> | |
| * | |
| * <p>This is a linear congruential pseudorandom number generator, as | |
| * defined by D. H. Lehmer and described by Donald E. Knuth in | |
| * <cite>The Art of Computer Programming, Volume 2, Third edition: | |
| * Seminumerical Algorithms</cite>, section 3.2.1. | |
| * | |
| * @param bits random bits | |
| * @return the next pseudorandom value from this random number | |
| * generator's sequence | |
| * @since 1.1 | |
| */ | |
| protected int next(int bits) { | |
| long oldseed, nextseed; | |
| AtomicLong seed = this.seed; | |
| do { | |
| oldseed = seed.get(); | |
| nextseed = (oldseed * multiplier + addend) & mask; | |
| } while (!seed.compareAndSet(oldseed, nextseed)); | |
| return (int)(nextseed >>> (48 - bits)); | |
| } | |
| /** | |
| * Generates random bytes and places them into a user-supplied | |
| * byte array. The number of random bytes produced is equal to | |
| * the length of the byte array. | |
| * | |
| * @implSpec The method {@code nextBytes} is | |
| * implemented by class {@code Random} as if by: | |
| * <pre>{@code | |
| * public void nextBytes(byte[] bytes) { | |
| * for (int i = 0; i < bytes.length; ) | |
| * for (int rnd = nextInt(), n = Math.min(bytes.length - i, 4); | |
| * n-- > 0; rnd >>= 8) | |
| * bytes[i++] = (byte)rnd; | |
| * }}</pre> | |
| * | |
| * @param bytes the byte array to fill with random bytes | |
| * @throws NullPointerException if the byte array is null | |
| * @since 1.1 | |
| */ | |
| @Override | |
| public void nextBytes(byte[] bytes) { | |
| for (int i = 0, len = bytes.length; i < len; ) | |
| for (int rnd = nextInt(), | |
| n = Math.min(len - i, Integer.SIZE/Byte.SIZE); | |
| n-- > 0; rnd >>= Byte.SIZE) | |
| bytes[i++] = (byte)rnd; | |
| } | |
| /** | |
| * Returns the next pseudorandom, uniformly distributed {@code int} | |
| * value from this random number generator's sequence. The general | |
| * contract of {@code nextInt} is that one {@code int} value is | |
| * pseudorandomly generated and returned. All 2<sup>32</sup> possible | |
| * {@code int} values are produced with (approximately) equal probability. | |
| * | |
| * @implSpec The method {@code nextInt} is | |
| * implemented by class {@code Random} as if by: | |
| * <pre>{@code | |
| * public int nextInt() { | |
| * return next(32); | |
| * }}</pre> | |
| * | |
| * @return the next pseudorandom, uniformly distributed {@code int} | |
| * value from this random number generator's sequence | |
| */ | |
| @Override | |
| public int nextInt() { | |
| return next(32); | |
| } | |
| /** | |
| * Returns a pseudorandom, uniformly distributed {@code int} value | |
| * between 0 (inclusive) and the specified value (exclusive), drawn from | |
| * this random number generator's sequence. The general contract of | |
| * {@code nextInt} is that one {@code int} value in the specified range | |
| * is pseudorandomly generated and returned. All {@code bound} possible | |
| * {@code int} values are produced with (approximately) equal | |
| * probability. | |
| * | |
| * @implSpec The method {@code nextInt(int bound)} is implemented by | |
| * class {@code Random} as if by: | |
| * <pre>{@code | |
| * public int nextInt(int bound) { | |
| * if (bound <= 0) | |
| * throw new IllegalArgumentException("bound must be positive"); | |
| * | |
| * if ((bound & -bound) == bound) // i.e., bound is a power of 2 | |
| * return (int)((bound * (long)next(31)) >> 31); | |
| * | |
| * int bits, val; | |
| * do { | |
| * bits = next(31); | |
| * val = bits % bound; | |
| * } while (bits - val + (bound-1) < 0); | |
| * return val; | |
| * }}</pre> | |
| * | |
| * <p>The hedge "approximately" is used in the foregoing description only | |
| * because the 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 int} | |
| * values from the stated range with perfect uniformity. | |
| * <p> | |
| * The algorithm is slightly tricky. It rejects values that would result | |
| * in an uneven distribution (due to the fact that 2^31 is not divisible | |
| * by n). The probability of a value being rejected depends on n. The | |
| * worst case is n=2^30+1, for which the probability of a reject is 1/2, | |
| * and the expected number of iterations before the loop terminates is 2. | |
| * <p> | |
| * The algorithm treats the case where n is a power of two specially: it | |
| * returns the correct number of high-order bits from the underlying | |
| * pseudo-random number generator. In the absence of special treatment, | |
| * the correct number of <i>low-order</i> bits would be returned. Linear | |
| * congruential pseudo-random number generators such as the one | |
| * implemented by this class are known to have short periods in the | |
| * sequence of values of their low-order bits. Thus, this special case | |
| * greatly increases the length of the sequence of values returned by | |
| * successive calls to this method if n is a small power of two. | |
| * | |
| * @param bound the upper bound (exclusive). Must be positive. | |
| * @return the next pseudorandom, uniformly distributed {@code int} | |
| * value between zero (inclusive) and {@code bound} (exclusive) | |
| * from this random number generator's sequence | |
| * @throws IllegalArgumentException if bound is not positive | |
| * @since 1.2 | |
| */ | |
| @Override | |
| public int nextInt(int bound) { | |
| if (bound <= 0) | |
| throw new IllegalArgumentException(BAD_BOUND); | |
| int r = next(31); | |
| int m = bound - 1; | |
| if ((bound & m) == 0) // i.e., bound is a power of 2 | |
| r = (int)((bound * (long)r) >> 31); | |
| else { // reject over-represented candidates | |
| for (int u = r; | |
| u - (r = u % bound) + m < 0; | |
| u = next(31)) | |
| ; | |
| } | |
| return r; | |
| } | |
| /** | |
| * Returns the next pseudorandom, uniformly distributed {@code long} | |
| * value from this random number generator's sequence. The general | |
| * contract of {@code nextLong} is that one {@code long} value is | |
| * pseudorandomly generated and returned. | |
| * | |
| * @implSpec The method {@code nextLong} is implemented by class {@code Random} | |
| * as if by: | |
| * <pre>{@code | |
| * public long nextLong() { | |
| * return ((long)next(32) << 32) + next(32); | |
| * }}</pre> | |
| * | |
| * Because class {@code Random} uses a seed with only 48 bits, | |
| * this algorithm will not return all possible {@code long} values. | |
| * | |
| * @return the next pseudorandom, uniformly distributed {@code long} | |
| * value from this random number generator's sequence | |
| */ | |
| @Override | |
| public long nextLong() { | |
| // it's okay that the bottom word remains signed. | |
| return ((long)(next(32)) << 32) + next(32); | |
| } | |
| /** | |
| * Returns the next pseudorandom, uniformly distributed | |
| * {@code boolean} value from this random number generator's | |
| * sequence. The general contract of {@code nextBoolean} is that one | |
| * {@code boolean} value is pseudorandomly generated and returned. The | |
| * values {@code true} and {@code false} are produced with | |
| * (approximately) equal probability. | |
| * | |
| * @implSpec The method {@code nextBoolean} is implemented by class | |
| * {@code Random} as if by: | |
| * <pre>{@code | |
| * public boolean nextBoolean() { | |
| * return next(1) != 0; | |
| * }}</pre> | |
| * | |
| * @return the next pseudorandom, uniformly distributed | |
| * {@code boolean} value from this random number generator's | |
| * sequence | |
| * @since 1.2 | |
| */ | |
| @Override | |
| public boolean nextBoolean() { | |
| return next(1) != 0; | |
| } | |
| /** | |
| * Returns the next pseudorandom, uniformly distributed {@code float} | |
| * value between {@code 0.0} and {@code 1.0} from this random | |
| * number generator's sequence. | |
| * | |
| * <p>The general contract of {@code nextFloat} is that one | |
| * {@code float} value, chosen (approximately) uniformly from the | |
| * range {@code 0.0f} (inclusive) to {@code 1.0f} (exclusive), is | |
| * pseudorandomly generated and returned. All 2<sup>24</sup> possible | |
| * {@code float} values of the form <i>m x </i>2<sup>-24</sup>, | |
| * where <i>m</i> is a positive integer less than 2<sup>24</sup>, are | |
| * produced with (approximately) equal probability. | |
| * | |
| * @implSpec The method {@code nextFloat} is implemented by class | |
| * {@code Random} as if by: | |
| * <pre>{@code | |
| * public float nextFloat() { | |
| * return next(24) / ((float)(1 << 24)); | |
| * }}</pre> | |
| * <p>The hedge "approximately" is used in the foregoing description only | |
| * because the 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 float} | |
| * values from the stated range with perfect uniformity.<p> | |
| * [In early versions of Java, the result was incorrectly calculated as: | |
| * <pre> {@code return next(30) / ((float)(1 << 30));}</pre> | |
| * This might seem to be equivalent, if not better, but in fact it | |
| * introduced a slight nonuniformity because of the bias in the rounding | |
| * of floating-point numbers: it was slightly more likely that the | |
| * low-order bit of the significand would be 0 than that it would be 1.] | |
| * | |
| * @return the next pseudorandom, uniformly distributed {@code float} | |
| * value between {@code 0.0f} and {@code 1.0f} from this | |
| * random number generator's sequence | |
| */ | |
| @Override | |
| public float nextFloat() { | |
| return next(Float.PRECISION) * FLOAT_UNIT; | |
| } | |
| /** | |
| * Returns the next pseudorandom, uniformly distributed | |
| * {@code double} value between {@code 0.0} and | |
| * {@code 1.0} from this random number generator's sequence. | |
| * | |
| * <p>The general contract of {@code nextDouble} is that one | |
| * {@code double} value, chosen (approximately) uniformly from the | |
| * range {@code 0.0d} (inclusive) to {@code 1.0d} (exclusive), is | |
| * pseudorandomly generated and returned. | |
| * | |
| * @implSpec The method {@code nextDouble} is implemented by class | |
| * {@code Random} as if by: | |
| * <pre>{@code | |
| * public double nextDouble() { | |
| * return (((long)next(26) << 27) + next(27)) | |
| * / (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(Double.PRECISION - 27)) << 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() { | |
| return AbstractSpliteratorGenerator.ints(this); | |
| } | |
| /** | |
| * 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) { | |
| return AbstractSpliteratorGenerator.ints(this, streamSize, randomNumberOrigin, randomNumberBound); | |
| } | |
| /** | |
| * 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) { | |
| return AbstractSpliteratorGenerator.ints(this, 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). | |
| * | |
| * @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 {@inheritDoc} | |
| * @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). | |
| * @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 {@inheritDoc} | |
| * @since 1.8 | |
| */ | |
| @Override | |
| public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { | |
| return AbstractSpliteratorGenerator.doubles(this, randomNumberOrigin, randomNumberBound); | |
| } | |
| } |