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/*
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* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.util;
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import java.math.BigInteger;
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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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/**
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* The {@code Rng} interface is designed to provide a common protocol
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* for objects that generate random or (more typically) pseudorandom
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* sequences of numbers (or Boolean values). Such a sequence may be
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* obtained by either repeatedly invoking a method that returns a
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* single (pseudo)randomly chosen value, or by invoking a method that
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* returns a stream of (pseudo)randomly chosen values.
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*
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* <p>Ideally, given an implicitly or explicitly specified range of values,
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* each value would be chosen independently and uniformly from that range.
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* In practice, one may have to settle for some approximation to independence
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* and uniformity.
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*
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* <p>In the case of {@code int}, {@code long}, and {@code Boolean}
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* values, if there is no explicit specification of range, then the
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* range includes all possible values of the type. In the case of
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* {@code float} and {@code double} values, a value is always chosen
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* from the set of 2<sup><i>w</i></sup> values between 0.0 (inclusive)
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* and 1.0 (exclusive), where <i>w</i> is 23 for {@code float}
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* values and 52 for {@code double} values, such that adjacent values
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* differ by 2<sup>−<i>w</i></sup>; if an explicit range is
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* specified, then the chosen number is computationally scaled and
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* translated so as to appear to have been chosen from that range.
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*
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* <p>Each method that returns a stream produces a stream of values each of
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* which is chosen in the same manner as for a method that
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* returns a single (pseudo)randomly chosen value. For example, if {@code r}
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* implements {@code Rng}, then the method call {@code r.ints(100)} returns
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* a stream of 100 {@code int} values. These are not necessarily the exact
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* same values that would have been returned if instead {@code r.nextInt()}
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* had been called 100 times; all that is guaranteed is that each value in
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* the stream is chosen in a similar (pseudo)random manner from the same range.
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*
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* <p>Every object that implements the {@code Rng} interface is assumed
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* to contain a finite amount of state. Using such an object to
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* generate a pseudorandomly chosen value alters its state. The
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* number of distinct possible states of such an object is called its
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* <i>period</i>. (Some implementations of the {@code Rng} interface
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* may be truly random rather than pseudorandom, for example relying
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* on the statistical behavior of a physical object to derive chosen
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* values. Such implementations do not have a fixed period.)
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*
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* <p>As a rule, objects that implement the {@code Rng} interface need not
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* be thread-safe. It is recommended that multithreaded applications
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* use either {@code ThreadLocalRandom} or (preferably) pseudorandom
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* number generators that implement the {@code SplittableRng} or
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* {@code JumpableRng} interface.
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* To implement this interface, a class only needs to provide concrete
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* definitions for the methods {@code nextLong()} and {@code period()}.
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* Default implementations are provided for all other methods
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* (but it may be desirable to override some of them, especially
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* {@code nextInt()} if the underlying algorithm is {@code int}-based).
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* Moerover, it may be preferable instead to implement another interface
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* such as {@link java.util.JumpableRng} or {@link java.util.LeapableRng},
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* or to extend an abstract class such as {@link java.util.AbstractSplittableRng}
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* or {@link java.util.AbstractArbitrarilyJumpableRng}.
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*
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* <p>Objects that implement {@code java.util.Rng} are typically
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* not cryptographically secure. Consider instead using
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* {@link java.security.SecureRandom} to get a cryptographically
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* secure pseudorandom number generator for use by
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* security-sensitive applications. Note, however, that
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* {@code java.security.SecureRandom} does implement the {@code Rng}
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* interface, so that instances of {@code java.security.SecureRandom}
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* may be used interchangeably with other types of pseudorandom
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* generators in applications that do not require a secure generator.
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*
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* @author Guy Steele
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* @since 1.9
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*/
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public interface Rng {
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/**
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* Returns an effectively unlimited stream of pseudorandomly chosen
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* {@code double} values.
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*
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* @implNote It is permitted to implement this method in a manner
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* equivalent to {@code doubles(Long.MAX_VALUE)}.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextDouble()}.
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*
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* @return a stream of pseudorandomly chosen {@code double} values
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*/
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default DoubleStream doubles() {
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return DoubleStream.generate(this::nextDouble).sequential();
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}
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/**
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* Returns an effectively unlimited stream of pseudorandomly chosen
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* {@code double} values, where each value is between the specified
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* origin (inclusive) and the specified bound (exclusive).
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*
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* @implNote It is permitted to implement this method in a manner
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* equivalent to
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* {@code doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextDouble(randomNumberOrigin, randomNumberBound)}.
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*
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* @param randomNumberOrigin the least value that can be produced
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* @param randomNumberBound the upper bound (exclusive) for each value produced
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* @return a stream of pseudorandomly chosen {@code double} values, each between
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* the specified origin (inclusive) and the specified bound (exclusive)
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* @throws IllegalArgumentException if {@code randomNumberOrigin}
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* is greater than or equal to {@code randomNumberBound}
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*/
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default DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
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RngSupport.checkRange(randomNumberOrigin, randomNumberBound);
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return DoubleStream.generate(() -> nextDouble(randomNumberOrigin, randomNumberBound)).sequential();
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}
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/**
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* Returns a stream producing the given {@code streamSize} number of
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* pseudorandomly chosen {@code double} values.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextDouble()}.
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*
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* @param streamSize the number of values to generate
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* @return a stream of pseudorandomly chosen {@code double} values
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* @throws IllegalArgumentException if {@code streamSize} is
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* less than zero
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*/
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default DoubleStream doubles(long streamSize) {
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RngSupport.checkStreamSize(streamSize);
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return doubles().limit(streamSize);
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}
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/**
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* Returns a stream producing the given {@code streamSize} number of
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* pseudorandomly chosen {@code double} values, where each value is between
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* the specified origin (inclusive) and the specified bound (exclusive).
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextDouble(randomNumberOrigin, randomNumberBound)}.
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*
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* @param streamSize the number of values to generate
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* @param randomNumberOrigin the least value that can be produced
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* @param randomNumberBound the upper bound (exclusive) for each value produced
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* @return a stream of pseudorandomly chosen {@code double} values, each between
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* the specified origin (inclusive) and the specified bound (exclusive)
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* @throws IllegalArgumentException if {@code streamSize} is
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* less than zero, or {@code randomNumberOrigin}
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* is greater than or equal to {@code randomNumberBound}
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*/
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default DoubleStream doubles(long streamSize, double randomNumberOrigin,
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double randomNumberBound) {
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RngSupport.checkStreamSize(streamSize);
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RngSupport.checkRange(randomNumberOrigin, randomNumberBound);
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return doubles(randomNumberOrigin, randomNumberBound).limit(streamSize);
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}
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/**
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* Returns an effectively unlimited stream of pseudorandomly chosen
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* {@code int} values.
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*
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* @implNote It is permitted to implement this method in a manner
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* equivalent to {@code ints(Long.MAX_VALUE)}.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextInt()}.
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*
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* @return a stream of pseudorandomly chosen {@code int} values
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*/
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default IntStream ints() {
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return IntStream.generate(this::nextInt).sequential();
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}
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/**
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* Returns an effectively unlimited stream of pseudorandomly chosen
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* {@code int} values, where each value is between the specified
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* origin (inclusive) and the specified bound (exclusive).
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*
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* @implNote It is permitted to implement this method in a manner
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* equivalent to
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* {@code ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextInt(randomNumberOrigin, randomNumberBound)}.
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*
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* @param randomNumberOrigin the least value that can be produced
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* @param randomNumberBound the upper bound (exclusive) for each value produced
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* @return a stream of pseudorandomly chosen {@code int} values, each between
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* the specified origin (inclusive) and the specified bound (exclusive)
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* @throws IllegalArgumentException if {@code randomNumberOrigin}
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* is greater than or equal to {@code randomNumberBound}
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*/
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default IntStream ints(int randomNumberOrigin, int randomNumberBound) {
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RngSupport.checkRange(randomNumberOrigin, randomNumberBound);
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return IntStream.generate(() -> nextInt(randomNumberOrigin, randomNumberBound)).sequential();
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}
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/**
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* Returns a stream producing the given {@code streamSize} number of
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* pseudorandomly chosen {@code int} values.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextInt()}.
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*
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* @param streamSize the number of values to generate
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* @return a stream of pseudorandomly chosen {@code int} values
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* @throws IllegalArgumentException if {@code streamSize} is
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* less than zero
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*/
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default IntStream ints(long streamSize) {
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RngSupport.checkStreamSize(streamSize);
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return ints().limit(streamSize);
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}
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/**
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* Returns a stream producing the given {@code streamSize} number of
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* pseudorandomly chosen {@code int} values, where each value is between
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* the specified origin (inclusive) and the specified bound (exclusive).
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextInt(randomNumberOrigin, randomNumberBound)}.
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*
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* @param streamSize the number of values to generate
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* @param randomNumberOrigin the least value that can be produced
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* @param randomNumberBound the upper bound (exclusive) for each value produced
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* @return a stream of pseudorandomly chosen {@code int} values, each between
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* the specified origin (inclusive) and the specified bound (exclusive)
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* @throws IllegalArgumentException if {@code streamSize} is
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* less than zero, or {@code randomNumberOrigin}
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* is greater than or equal to {@code randomNumberBound}
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*/
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default IntStream ints(long streamSize, int randomNumberOrigin,
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int randomNumberBound) {
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RngSupport.checkStreamSize(streamSize);
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RngSupport.checkRange(randomNumberOrigin, randomNumberBound);
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return ints(randomNumberOrigin, randomNumberBound).limit(streamSize);
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}
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/**
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* Returns an effectively unlimited stream of pseudorandomly chosen
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* {@code long} values.
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*
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* @implNote It is permitted to implement this method in a manner
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* equivalent to {@code longs(Long.MAX_VALUE)}.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextLong()}.
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*
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* @return a stream of pseudorandomly chosen {@code long} values
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*/
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default LongStream longs() {
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return LongStream.generate(this::nextLong).sequential();
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}
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/**
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* Returns an effectively unlimited stream of pseudorandomly chosen
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* {@code long} values, where each value is between the specified
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* origin (inclusive) and the specified bound (exclusive).
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*
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* @implNote It is permitted to implement this method in a manner
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* equivalent to
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* {@code longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextLong(randomNumberOrigin, randomNumberBound)}.
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*
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* @param randomNumberOrigin the least value that can be produced
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* @param randomNumberBound the upper bound (exclusive) for each value produced
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* @return a stream of pseudorandomly chosen {@code long} values, each between
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* the specified origin (inclusive) and the specified bound (exclusive)
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* @throws IllegalArgumentException if {@code randomNumberOrigin}
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* is greater than or equal to {@code randomNumberBound}
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*/
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default LongStream longs(long randomNumberOrigin, long randomNumberBound) {
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RngSupport.checkRange(randomNumberOrigin, randomNumberBound);
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return LongStream.generate(() -> nextLong(randomNumberOrigin, randomNumberBound)).sequential();
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}
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/**
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* Returns a stream producing the given {@code streamSize} number of
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* pseudorandomly chosen {@code long} values.
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextLong()}.
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*
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* @param streamSize the number of values to generate
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* @return a stream of pseudorandomly chosen {@code long} values
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* @throws IllegalArgumentException if {@code streamSize} is
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* less than zero
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*/
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default LongStream longs(long streamSize) {
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RngSupport.checkStreamSize(streamSize);
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return longs().limit(streamSize);
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}
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/**
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* Returns a stream producing the given {@code streamSize} number of
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* pseudorandomly chosen {@code long} values, where each value is between
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* the specified origin (inclusive) and the specified bound (exclusive).
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*
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* @implNote The default implementation produces a sequential stream
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* that repeatedly calls {@code nextLong(randomNumberOrigin, randomNumberBound)}.
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*
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* @param streamSize the number of values to generate
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* @param randomNumberOrigin the least value that can be produced
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339 |
* @param randomNumberBound the upper bound (exclusive) for each value produced
|
|
|
340 |
* @return a stream of pseudorandomly chosen {@code long} values, each between
|
|
|
341 |
* the specified origin (inclusive) and the specified bound (exclusive)
|
|
|
342 |
* @throws IllegalArgumentException if {@code streamSize} is
|
|
|
343 |
* less than zero, or {@code randomNumberOrigin}
|
|
|
344 |
* is greater than or equal to {@code randomNumberBound}
|
|
|
345 |
*/
|
|
|
346 |
default LongStream longs(long streamSize, long randomNumberOrigin,
|
|
|
347 |
long randomNumberBound) {
|
|
|
348 |
RngSupport.checkStreamSize(streamSize);
|
|
|
349 |
RngSupport.checkRange(randomNumberOrigin, randomNumberBound);
|
|
|
350 |
return longs(randomNumberOrigin, randomNumberBound).limit(streamSize);
|
|
|
351 |
}
|
|
|
352 |
|
|
|
353 |
/**
|
|
|
354 |
* Returns a pseudorandomly chosen {@code boolean} value.
|
|
|
355 |
*
|
|
|
356 |
* <p>The default implementation tests the high-order bit (sign bit)
|
|
|
357 |
* of a value produced by {@code nextInt()}, on the grounds
|
|
|
358 |
* that some algorithms for pseudorandom number generation
|
|
|
359 |
* produce values whose high-order bits have better
|
|
|
360 |
* statistical quality than the low-order bits.
|
|
|
361 |
*
|
|
|
362 |
* @return a pseudorandomly chosen {@code boolean} value
|
|
|
363 |
*/
|
|
|
364 |
default boolean nextBoolean() {
|
|
|
365 |
return nextInt() < 0;
|
|
|
366 |
}
|
|
|
367 |
|
|
|
368 |
/**
|
|
|
369 |
* Returns a pseudorandom {@code float} value between zero
|
|
|
370 |
* (inclusive) and one (exclusive).
|
|
|
371 |
*
|
|
|
372 |
* The default implementation uses the 24 high-order bits
|
|
|
373 |
* from a call to {@code nextInt()}.
|
|
|
374 |
*
|
|
|
375 |
* @return a pseudorandom {@code float} value between zero
|
|
|
376 |
* (inclusive) and one (exclusive)
|
|
|
377 |
*/
|
|
|
378 |
default float nextFloat() {
|
|
|
379 |
return (nextInt() >>> 8) * 0x1.0p-24f;
|
|
|
380 |
}
|
|
|
381 |
|
|
|
382 |
/**
|
|
|
383 |
* Returns a pseudorandomly chosen {@code float} value between zero
|
|
|
384 |
* (inclusive) and the specified bound (exclusive).
|
|
|
385 |
*
|
|
|
386 |
* @implNote The default implementation simply calls
|
|
|
387 |
* {@code RngSupport.checkBound(bound)} and then
|
|
|
388 |
* {@code RngSupport.boundedNextFloat(this, bound)}.
|
|
|
389 |
*
|
|
|
390 |
* @param bound the upper bound (exclusive) for the returned value.
|
|
|
391 |
* Must be positive and finite
|
|
|
392 |
* @return a pseudorandomly chosen {@code float} value between
|
|
|
393 |
* zero (inclusive) and the bound (exclusive)
|
|
|
394 |
* @throws IllegalArgumentException if {@code bound} is not
|
|
|
395 |
* positive and finite
|
|
|
396 |
*/
|
|
|
397 |
default float nextFloat(float bound) {
|
|
|
398 |
RngSupport.checkBound(bound);
|
|
|
399 |
return RngSupport.boundedNextFloat(this, bound);
|
|
|
400 |
}
|
|
|
401 |
|
|
|
402 |
/**
|
|
|
403 |
* Returns a pseudorandomly chosen {@code float} value between the
|
|
|
404 |
* specified origin (inclusive) and the specified bound (exclusive).
|
|
|
405 |
*
|
|
|
406 |
* @implNote The default implementation simply calls
|
|
|
407 |
* {@code RngSupport.checkRange(origin, bound)} and then
|
|
|
408 |
* {@code RngSupport.boundedNextFloat(this, origin, bound)}.
|
|
|
409 |
*
|
|
|
410 |
* @param origin the least value that can be returned
|
|
|
411 |
* @param bound the upper bound (exclusive)
|
|
|
412 |
* @return a pseudorandomly chosen {@code float} value between the
|
|
|
413 |
* origin (inclusive) and the bound (exclusive)
|
|
|
414 |
* @throws IllegalArgumentException unless {@code origin} is finite,
|
|
|
415 |
* {@code bound} is finite, and {@code origin} is less than
|
|
|
416 |
* {@code bound}
|
|
|
417 |
*/
|
|
|
418 |
default float nextFloat(float origin, float bound) {
|
|
|
419 |
RngSupport.checkRange(origin, bound);
|
|
|
420 |
return RngSupport.boundedNextFloat(this, origin, bound);
|
|
|
421 |
}
|
|
|
422 |
|
|
|
423 |
/**
|
|
|
424 |
* Returns a pseudorandom {@code double} value between zero
|
|
|
425 |
* (inclusive) and one (exclusive).
|
|
|
426 |
*
|
|
|
427 |
* The default implementation uses the 53 high-order bits
|
|
|
428 |
* from a call to {@code nextLong()}.
|
|
|
429 |
*
|
|
|
430 |
* @return a pseudorandom {@code double} value between zero
|
|
|
431 |
* (inclusive) and one (exclusive)
|
|
|
432 |
*/
|
|
|
433 |
default double nextDouble() {
|
|
|
434 |
return (nextLong() >>> 11) * 0x1.0p-53;
|
|
|
435 |
}
|
|
|
436 |
|
|
|
437 |
/**
|
|
|
438 |
* Returns a pseudorandomly chosen {@code double} value between zero
|
|
|
439 |
* (inclusive) and the specified bound (exclusive).
|
|
|
440 |
*
|
|
|
441 |
* @implNote The default implementation simply calls
|
|
|
442 |
* {@code RngSupport.checkBound(bound)} and then
|
|
|
443 |
* {@code RngSupport.boundedNextDouble(this, bound)}.
|
|
|
444 |
*
|
|
|
445 |
* @param bound the upper bound (exclusive) for the returned value.
|
|
|
446 |
* Must be positive and finite
|
|
|
447 |
* @return a pseudorandomly chosen {@code double} value between
|
|
|
448 |
* zero (inclusive) and the bound (exclusive)
|
|
|
449 |
* @throws IllegalArgumentException if {@code bound} is not
|
|
|
450 |
* positive and finite
|
|
|
451 |
*/
|
|
|
452 |
default double nextDouble(double bound) {
|
|
|
453 |
RngSupport.checkBound(bound);
|
|
|
454 |
return RngSupport.boundedNextDouble(this, bound);
|
|
|
455 |
}
|
|
|
456 |
|
|
|
457 |
/**
|
|
|
458 |
* Returns a pseudorandomly chosen {@code double} value between the
|
|
|
459 |
* specified origin (inclusive) and the specified bound (exclusive).
|
|
|
460 |
*
|
|
|
461 |
* @implNote The default implementation simply calls
|
|
|
462 |
* {@code RngSupport.checkRange(origin, bound)} and then
|
|
|
463 |
* {@code RngSupport.boundedNextDouble(this, origin, bound)}.
|
|
|
464 |
*
|
|
|
465 |
* @param origin the least value that can be returned
|
|
|
466 |
* @param bound the upper bound (exclusive) for the returned value
|
|
|
467 |
* @return a pseudorandomly chosen {@code double} value between the
|
|
|
468 |
* origin (inclusive) and the bound (exclusive)
|
|
|
469 |
* @throws IllegalArgumentException unless {@code origin} is finite,
|
|
|
470 |
* {@code bound} is finite, and {@code origin} is less than
|
|
|
471 |
* {@code bound}
|
|
|
472 |
*/
|
|
|
473 |
default double nextDouble(double origin, double bound) {
|
|
|
474 |
RngSupport.checkRange(origin, bound);
|
|
|
475 |
return RngSupport.boundedNextDouble(this, origin, bound);
|
|
|
476 |
}
|
|
|
477 |
|
|
|
478 |
/**
|
|
|
479 |
* Returns a pseudorandomly chosen {@code int} value.
|
|
|
480 |
*
|
|
|
481 |
* The default implementation uses the 32 high-order bits
|
|
|
482 |
* from a call to {@code nextLong()}.
|
|
|
483 |
*
|
|
|
484 |
* @return a pseudorandomly chosen {@code int} value
|
|
|
485 |
*/
|
|
|
486 |
default public int nextInt() {
|
|
|
487 |
return (int)(nextLong() >>> 32);
|
|
|
488 |
}
|
|
|
489 |
|
|
|
490 |
/**
|
|
|
491 |
* Returns a pseudorandomly chosen {@code int} value between
|
|
|
492 |
* zero (inclusive) and the specified bound (exclusive).
|
|
|
493 |
*
|
|
|
494 |
* @implNote The default implementation simply calls
|
|
|
495 |
* {@code RngSupport.checkBound(bound)} and then
|
|
|
496 |
* {@code RngSupport.boundedNextInt(this, bound)}.
|
|
|
497 |
*
|
|
|
498 |
* @param bound the upper bound (exclusive) for the returned value. Must be positive.
|
|
|
499 |
* @return a pseudorandomly chosen {@code int} value between
|
|
|
500 |
* zero (inclusive) and the bound (exclusive)
|
|
|
501 |
* @throws IllegalArgumentException if {@code bound} is not positive
|
|
|
502 |
*/
|
|
|
503 |
default int nextInt(int bound) {
|
|
|
504 |
RngSupport.checkBound(bound);
|
|
|
505 |
return RngSupport.boundedNextInt(this, bound);
|
|
|
506 |
}
|
|
|
507 |
|
|
|
508 |
/**
|
|
|
509 |
* Returns a pseudorandomly chosen {@code int} value between the
|
|
|
510 |
* specified origin (inclusive) and the specified bound (exclusive).
|
|
|
511 |
*
|
|
|
512 |
* @implNote The default implementation simply calls
|
|
|
513 |
* {@code RngSupport.checkRange(origin, bound)} and then
|
|
|
514 |
* {@code RngSupport.boundedNextInt(this, origin, bound)}.
|
|
|
515 |
*
|
|
|
516 |
* @param origin the least value that can be returned
|
|
|
517 |
* @param bound the upper bound (exclusive) for the returned value
|
|
|
518 |
* @return a pseudorandomly chosen {@code int} value between the
|
|
|
519 |
* origin (inclusive) and the bound (exclusive)
|
|
|
520 |
* @throws IllegalArgumentException if {@code origin} is greater than
|
|
|
521 |
* or equal to {@code bound}
|
|
|
522 |
*/
|
|
|
523 |
default int nextInt(int origin, int bound) {
|
|
|
524 |
RngSupport.checkRange(origin, bound);
|
|
|
525 |
return RngSupport.boundedNextInt(this, origin, bound);
|
|
|
526 |
}
|
|
|
527 |
|
|
|
528 |
/**
|
|
|
529 |
* Returns a pseudorandomly chosen {@code long} value.
|
|
|
530 |
*
|
|
|
531 |
* @return a pseudorandomly chosen {@code long} value
|
|
|
532 |
*/
|
|
|
533 |
long nextLong();
|
|
|
534 |
|
|
|
535 |
/**
|
|
|
536 |
* Returns a pseudorandomly chosen {@code long} value between
|
|
|
537 |
* zero (inclusive) and the specified bound (exclusive).
|
|
|
538 |
*
|
|
|
539 |
* @implNote The default implementation simply calls
|
|
|
540 |
* {@code RngSupport.checkBound(bound)} and then
|
|
|
541 |
* {@code RngSupport.boundedNextLong(this, bound)}.
|
|
|
542 |
*
|
|
|
543 |
* @param bound the upper bound (exclusive) for the returned value. Must be positive.
|
|
|
544 |
* @return a pseudorandomly chosen {@code long} value between
|
|
|
545 |
* zero (inclusive) and the bound (exclusive)
|
|
|
546 |
* @throws IllegalArgumentException if {@code bound} is not positive
|
|
|
547 |
*/
|
|
|
548 |
default long nextLong(long bound) {
|
|
|
549 |
RngSupport.checkBound(bound);
|
|
|
550 |
return RngSupport.boundedNextLong(this, bound);
|
|
|
551 |
}
|
|
|
552 |
|
|
|
553 |
/**
|
|
|
554 |
* Returns a pseudorandomly chosen {@code long} value between the
|
|
|
555 |
* specified origin (inclusive) and the specified bound (exclusive).
|
|
|
556 |
*
|
|
|
557 |
* @implNote The default implementation simply calls
|
|
|
558 |
* {@code RngSupport.checkRange(origin, bound)} and then
|
|
|
559 |
* {@code RngSupport.boundedNextInt(this, origin, bound)}.
|
|
|
560 |
*
|
|
|
561 |
* @param origin the least value that can be returned
|
|
|
562 |
* @param bound the upper bound (exclusive) for the returned value
|
|
|
563 |
* @return a pseudorandomly chosen {@code long} value between the
|
|
|
564 |
* origin (inclusive) and the bound (exclusive)
|
|
|
565 |
* @throws IllegalArgumentException if {@code origin} is greater than
|
|
|
566 |
* or equal to {@code bound}
|
|
|
567 |
*/
|
|
|
568 |
default long nextLong(long origin, long bound) {
|
|
|
569 |
RngSupport.checkRange(origin, bound);
|
|
|
570 |
return RngSupport.boundedNextLong(this, origin, bound);
|
|
|
571 |
}
|
|
|
572 |
|
|
|
573 |
/**
|
|
|
574 |
* Returns a {@code double} value pseudorandomly chosen from
|
|
|
575 |
* a Gaussian (normal) distribution whose mean is 0 and whose
|
|
|
576 |
* standard deviation is 1.
|
|
|
577 |
*
|
|
|
578 |
* @return a {@code double} value pseudorandomly chosen from a
|
|
|
579 |
* Gaussian distribution
|
|
|
580 |
*/
|
|
|
581 |
default double nextGaussian() {
|
|
|
582 |
return RngSupport.computeNextGaussian(this);
|
|
|
583 |
}
|
|
|
584 |
|
|
|
585 |
/**
|
|
|
586 |
* Returns a {@code double} value pseudorandomly chosen from
|
|
|
587 |
* a Gaussian (normal) distribution with a mean and
|
|
|
588 |
* standard deviation specified by the arguments.
|
|
|
589 |
*
|
|
|
590 |
* @param mean the mean of the Gaussian distribution to be drawn from
|
|
|
591 |
* @param stddev the standard deviation (square root of the variance)
|
|
|
592 |
* of the Gaussian distribution to be drawn from
|
|
|
593 |
* @return a {@code double} value pseudorandomly chosen from the
|
|
|
594 |
* specified Gaussian distribution
|
|
|
595 |
* @throws IllegalArgumentException if {@code stddev} is negative
|
|
|
596 |
*/
|
|
|
597 |
default double nextGaussian(double mean, double stddev) {
|
|
|
598 |
if (stddev < 0.0) throw new IllegalArgumentException("standard deviation must be non-negative");
|
|
|
599 |
return mean + stddev * RngSupport.computeNextGaussian(this);
|
|
|
600 |
}
|
|
|
601 |
|
|
|
602 |
/**
|
|
|
603 |
* Returns a nonnegative {@code double} value pseudorandomly chosen
|
|
|
604 |
* from an exponential distribution whose mean is 1.
|
|
|
605 |
*
|
|
|
606 |
* @return a nonnegative {@code double} value pseudorandomly chosen from an
|
|
|
607 |
* exponential distribution
|
|
|
608 |
*/
|
|
|
609 |
default double nextExponential() {
|
|
|
610 |
return RngSupport.computeNextExponential(this);
|
|
|
611 |
}
|
|
|
612 |
|
|
|
613 |
/**
|
|
|
614 |
* Returns the period of this {@code Rng} object.
|
|
|
615 |
*
|
|
|
616 |
* @return a {@code BigInteger} whose value is the number of
|
|
|
617 |
* distinct possible states of this {@code Rng} object,
|
|
|
618 |
* or 0 if unknown, or negative if extremely large.
|
|
|
619 |
*/
|
|
|
620 |
BigInteger period();
|
|
|
621 |
|
|
|
622 |
/**
|
|
|
623 |
* The value (0) returned by the {@code period()} method if the period is unknown.
|
|
|
624 |
*/
|
|
|
625 |
static final BigInteger UNKNOWN_PERIOD = BigInteger.ZERO;
|
|
|
626 |
|
|
|
627 |
/**
|
|
|
628 |
* The (negative) value returned by the {@code period()} method if this generator
|
|
|
629 |
* has no period because it is truly random rather than just pseudorandom.
|
|
|
630 |
*/
|
|
|
631 |
static final BigInteger TRULY_RANDOM = BigInteger.valueOf(-1);
|
|
|
632 |
|
|
|
633 |
/**
|
|
|
634 |
* The (negative) value that may be returned by the {@code period()} method
|
|
|
635 |
* if this generator has a huge period (larger than 2**(2**16)).
|
|
|
636 |
*/
|
|
|
637 |
static final BigInteger HUGE_PERIOD = BigInteger.valueOf(-2);
|
|
|
638 |
}
|