OpenJDK 27 · jdk.internal.random.L64X128StarStarRandom

A "splittable" pseudorandom number generator (PRNG) whose period is roughly 2¹⁹². Class L64X128StarStarRandom implements interfaces RandomGenerator and SplittableGenerator, and therefore supports methods for producing pseudorandomly chosen values of type int, long, float, double, and boolean (and for producing streams of pseudorandomly chosen numbers of type int, long, and double), as well as methods for creating new split-off L64X128StarStarRandom objects or streams of such objects.

The L64X128StarStarRandom algorithm is a specific member of the LXM family of algorithms for pseudorandom number generators; for more information, see the documentation for package jdk.random. Each instance of L64X128StarStarRandom has 192 bits of state plus one 64-bit instance-specific parameter.

If two instances of L64X128StarStarRandom are created with the same seed within the same program execution, and the same sequence of method calls is made for each, they will generate and return identical sequences of values.

As with java.util.SplittableRandom, instances of L64X128StarStarRandom are not thread-safe. They are designed to be split, not shared, across threads (see the split method). For example, a java.util.concurrent.ForkJoinTask fork/join-style computation using random numbers might include a construction of the form new Subtask(someL64X128StarStarRandom.split()).fork().

This class provides additional methods for generating random streams, that employ the above techniques when used in stream.parallel() mode.

Instances of L64X128StarStarRandom are not cryptographically secure. Consider instead using java.security.SecureRandom in security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless the system property java.util.secureRandomSeed is set to true.

Modifier and Type	Field and Description
private final long	a The parameter that is used as an additive constant for the LCG.
private static final AtomicLong	defaultGen The seed generator for default constructors.
private static final long	M
private long	s The per-instance state: s for the LCG; x0 and x1 for the XBG.
private long	x0 The per-instance state: s for the LCG; x0 and x1 for the XBG.
private long	x1 The per-instance state: s for the LCG; x0 and x1 for the XBG.

Constructor Summary

Access	Constructor and Description
public	L64X128StarStarRandom(long additive parameter for the LCG a, long initial state for the LCG s, long first word of the initial state for the XBG x0, long second word of the initial state for the XBG x1) Basic constructor that initializes all fields from parameters.
public	L64X128StarStarRandom(long the initial seed seed) Creates a new instance of `L64X128StarStarRandom` using the specified `long` value as the initial seed.
public	L64X128StarStarRandom() Creates a new instance of `L64X128StarStarRandom` that is likely to generate sequences of values that are statistically independent of those of any other instances in the current program execution, but may, and typically does, vary across program invocations.
public	L64X128StarStarRandom(byte[] the initial seed seed) Creates a new instance of `L64X128StarStarRandom` using the specified array of initial seed bytes.

Modifier and Type	Method and Description
public long	nextLong() Implements java.util.random.RandomGenerator.nextLong. Returns a pseudorandomly chosen `long` value.
public RandomGenerator.SplittableGenerator	split(RandomGenerator.SplittableGenerator source, long brine) Implements abstract jdk.internal.util.random.RandomSupport.AbstractSplittableWithBrineGenerator.split.

Field Detail

a	back to summary
private final long a The parameter that is used as an additive constant for the LCG. Must be odd.

defaultGen	back to summary
private static final AtomicLong defaultGen The seed generator for default constructors.

M	back to summary
private static final long M

s	back to summary
private long s The per-instance state: s for the LCG; x0 and x1 for the XBG. At least one of x0 and x1 must be nonzero.

x0	back to summary
private long x0 The per-instance state: s for the LCG; x0 and x1 for the XBG. At least one of x0 and x1 must be nonzero.

x1	back to summary
private long x1 The per-instance state: s for the LCG; x0 and x1 for the XBG. At least one of x0 and x1 must be nonzero.

Constructor Detail

L64X128StarStarRandom	back to summary
public L64X128StarStarRandom(long a, long s, long x0, long x1) Basic constructor that initializes all fields from parameters. It then adjusts the field values if necessary to ensure that all constraints on the values of fields are met. Parameters a:long additive parameter for the LCG s:long initial state for the LCG x0:long first word of the initial state for the XBG x1:long second word of the initial state for the XBG

L64X128StarStarRandom

back to summary

public L64X128StarStarRandom(long a, long s, long x0, long x1)

Basic constructor that initializes all fields from parameters. It then adjusts the field values if necessary to ensure that all constraints on the values of fields are met.

Parameters

a:long: additive parameter for the LCG
s:long: initial state for the LCG
x0:long: first word of the initial state for the XBG
x1:long: second word of the initial state for the XBG

L64X128StarStarRandom back to summary

L64X128StarStarRandom	back to summary
public L64X128StarStarRandom(long seed) Creates a new instance of `L64X128StarStarRandom` using the specified `long` value as the initial seed. Instances of `L64X128StarStarRandom` created with the same seed in the same program generate identical sequences of values. Parameters seed:long the initial seed

public L64X128StarStarRandom(long seed)

Creates a new instance of L64X128StarStarRandom using the specified long value as the initial seed. Instances of L64X128StarStarRandom created with the same seed in the same program generate identical sequences of values.

Parameters

seed:long: the initial seed

L64X128StarStarRandom	back to summary
public L64X128StarStarRandom() Creates a new instance of `L64X128StarStarRandom` that is likely to generate sequences of values that are statistically independent of those of any other instances in the current program execution, but may, and typically does, vary across program invocations.

L64X128StarStarRandom back to summary

L64X128StarStarRandom	back to summary
public L64X128StarStarRandom(byte[] seed) Creates a new instance of `L64X128StarStarRandom` using the specified array of initial seed bytes. Instances of `L64X128StarStarRandom` created with the same seed array in the same program execution generate identical sequences of values. Parameters seed:byte[] the initial seed

public L64X128StarStarRandom(byte[] seed)

Creates a new instance of L64X128StarStarRandom using the specified array of initial seed bytes. Instances of L64X128StarStarRandom created with the same seed array in the same program execution generate identical sequences of values.

Parameters

seed:byte[]: the initial seed

public final Class L64X128StarStarRandom

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