OpenJDK 27 · jdk.internal.random.Xoroshiro128PlusPlus

A "jumpable and leapable" pseudorandom number generator (PRNG) whose period is roughly 2¹²⁸. Class Xoroshiro128PlusPlus implements interfaces RandomGenerator and LeapableGenerator, and therefore supports methods for producing pseudorandomly chosen numbers of type int, long, float, and double as well as creating new Xoroshiro128PlusPlus objects by "jumping" or "leaping".

The class Xoroshiro128PlusPlus uses the xoroshiro128 algorithm (parameters 49, 21, 28) with the "++" scrambler that computes Long.rotateLeft(s0 + s1, 17) + s0. (See David Blackman and Sebastiano Vigna, "Scrambled Linear Pseudorandom Number Generators," ACM Transactions on Mathematical Software, 2021.) Its state consists of two long fields x0 and x1, which can take on any values provided that they are not both zero. The period of this generator is 2¹²⁸-1.

The 64-bit values produced by the nextLong() method are equidistributed. To be precise, over the course of the cycle of length 2¹²⁸-1, each nonzero long value is generated 2⁶⁴ times, but the value 0 is generated only 2⁶⁴-1 times. The values produced by the nextInt(), nextFloat(), and nextDouble() methods are likewise equidistributed.

Instances Xoroshiro128PlusPlus are not thread-safe. They are designed to be used so that each thread as its own instance. The methods jump and leap and jumps and leaps can be used to construct new instances of Xoroshiro128PlusPlus that traverse other parts of the state cycle.

Instances of Xoroshiro128PlusPlus 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 static final AtomicLong	defaultGen The seed generator for default constructors.
private static final String	GROUP Group name.
private static final long[]	JUMP_TABLE
private static final long[]	LEAP_TABLE
private long	x0 The per-instance state.
private long	x1 The per-instance state.

Constructor Summary

Access	Constructor and Description
public	Xoroshiro128PlusPlus(long first word of the initial state x0, long second word of the initial state x1) Basic constructor that initializes all fields from parameters.
public	Xoroshiro128PlusPlus(long the initial seed seed) Creates a new instance of `Xoroshiro128PlusPlus` using the specified `long` value as the initial seed.
public	Xoroshiro128PlusPlus() Creates a new instance of `Xoroshiro128PlusPlus` 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	Xoroshiro128PlusPlus(byte[] the initial seed seed) Creates a new instance of `Xoroshiro128PlusPlus` using the specified array of initial seed bytes.

Method Summary

Modifier and Type	Method and Description
public Xoroshiro128PlusPlus	copy() Implements java.util.random.RandomGenerator.LeapableGenerator.copy. Returns a new generator whose internal state is an exact copy of this generator (therefore their future behavior should be identical if subjected to the same series of operations).
public void	jump() Implements java.util.random.RandomGenerator.JumpableGenerator.jump. Alter the state of this pseudorandom number generator so as to jump forward a large, fixed distance (typically 2⁶⁴ or more) within its state cycle.
private void	jumpAlgorithm(long[] table)
public double	jumpDistance() Implements java.util.random.RandomGenerator.JumpableGenerator.jumpDistance. Returns the distance by which the `jump`() method will jump forward within the state cycle of this generator object.
public void	leap() Implements java.util.random.RandomGenerator.LeapableGenerator.leap. Alter the state of this pseudorandom number generator so as to leap forward a large, fixed distance (typically 2⁹⁶ or more) within its state cycle.
public double	leapDistance() Implements java.util.random.RandomGenerator.LeapableGenerator.leapDistance. Returns the distance by which the `leap`() method will leap forward within the state cycle of this generator object.
public long	nextLong() Implements java.util.random.RandomGenerator.nextLong. Returns a pseudorandomly chosen `long` value.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

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

GROUP	back to summary
private static final String GROUP Group name.

JUMP_TABLE	back to summary
private static final long[] JUMP_TABLE

LEAP_TABLE	back to summary
private static final long[] LEAP_TABLE

x0	back to summary
private long x0 The per-instance state. At least one of the two fields x0 and x1 must be nonzero.

x1	back to summary
private long x1 The per-instance state. At least one of the two fields x0 and x1 must be nonzero.

Constructor Detail

Xoroshiro128PlusPlus	back to summary
public Xoroshiro128PlusPlus(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 x0:long first word of the initial state x1:long second word of the initial state

Xoroshiro128PlusPlus

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public Xoroshiro128PlusPlus(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

x0:long: first word of the initial state
x1:long: second word of the initial state

Xoroshiro128PlusPlus back to summary

Xoroshiro128PlusPlus	back to summary
public Xoroshiro128PlusPlus(long seed) Creates a new instance of `Xoroshiro128PlusPlus` using the specified `long` value as the initial seed. Instances of `Xoroshiro128PlusPlus` created with the same seed in the same program generate identical sequences of values. Parameters seed:long the initial seed

public Xoroshiro128PlusPlus(long seed)

Creates a new instance of Xoroshiro128PlusPlus using the specified long value as the initial seed. Instances of Xoroshiro128PlusPlus created with the same seed in the same program generate identical sequences of values.

Parameters

seed:long: the initial seed

Xoroshiro128PlusPlus	back to summary
public Xoroshiro128PlusPlus() Creates a new instance of `Xoroshiro128PlusPlus` 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.

Xoroshiro128PlusPlus back to summary

Xoroshiro128PlusPlus	back to summary
public Xoroshiro128PlusPlus(byte[] seed) Creates a new instance of `Xoroshiro128PlusPlus` using the specified array of initial seed bytes. Instances of `Xoroshiro128PlusPlus` created with the same seed array in the same program execution generate identical sequences of values. Parameters seed:byte[] the initial seed

public Xoroshiro128PlusPlus(byte[] seed)

Creates a new instance of Xoroshiro128PlusPlus using the specified array of initial seed bytes. Instances of Xoroshiro128PlusPlus created with the same seed array in the same program execution generate identical sequences of values.

Parameters

seed:byte[]: the initial seed

Method Detail

copy	back to summary
public Xoroshiro128PlusPlus copy() Implements java.util.random.RandomGenerator.LeapableGenerator.copy. Doc from java.util.random.RandomGenerator.LeapableGenerator.copy. Returns a new generator whose internal state is an exact copy of this generator (therefore their future behavior should be identical if subjected to the same series of operations).

copy

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public Xoroshiro128PlusPlus copy()

Implements java.util.random.RandomGenerator.LeapableGenerator.copy.

Doc from java.util.random.RandomGenerator.LeapableGenerator.copy.

Returns a new generator whose internal state is an exact copy of this generator (therefore their future behavior should be identical if subjected to the same series of operations).

jump	back to summary
public void jump() Implements java.util.random.RandomGenerator.JumpableGenerator.jump. Doc from java.util.random.RandomGenerator.JumpableGenerator.jump. Alter the state of this pseudorandom number generator so as to jump forward a large, fixed distance (typically 2⁶⁴ or more) within its state cycle. Annotations @Override

jump

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public void jump()

Implements java.util.random.RandomGenerator.JumpableGenerator.jump.

Doc from java.util.random.RandomGenerator.JumpableGenerator.jump.

Alter the state of this pseudorandom number generator so as to jump forward a large, fixed distance (typically 2⁶⁴ or more) within its state cycle.

Annotations

@Override

jumpAlgorithm	back to summary
private void jumpAlgorithm(long[] table)

jumpDistance back to summary

jumpDistance	back to summary
public double jumpDistance() Implements java.util.random.RandomGenerator.JumpableGenerator.jumpDistance. Doc from java.util.random.RandomGenerator.JumpableGenerator.jumpDistance. Returns the distance by which the `jump`() method will jump forward within the state cycle of this generator object. Annotations @Override

public double jumpDistance()

Implements java.util.random.RandomGenerator.JumpableGenerator.jumpDistance.

Doc from java.util.random.RandomGenerator.JumpableGenerator.jumpDistance.

Returns the distance by which the jump() method will jump forward within the state cycle of this generator object.

Annotations

@Override

leap	back to summary
public void leap() Implements java.util.random.RandomGenerator.LeapableGenerator.leap. Doc from java.util.random.RandomGenerator.LeapableGenerator.leap. Alter the state of this pseudorandom number generator so as to leap forward a large, fixed distance (typically 2⁹⁶ or more) within its state cycle. Annotations @Override

leap

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public void leap()

Implements java.util.random.RandomGenerator.LeapableGenerator.leap.

Doc from java.util.random.RandomGenerator.LeapableGenerator.leap.

Alter the state of this pseudorandom number generator so as to leap forward a large, fixed distance (typically 2⁹⁶ or more) within its state cycle.

Annotations

@Override

leapDistance back to summary

leapDistance	back to summary
public double leapDistance() Implements java.util.random.RandomGenerator.LeapableGenerator.leapDistance. Doc from java.util.random.RandomGenerator.LeapableGenerator.leapDistance. Returns the distance by which the `leap`() method will leap forward within the state cycle of this generator object. Annotations @Override

public double leapDistance()

Implements java.util.random.RandomGenerator.LeapableGenerator.leapDistance.

Doc from java.util.random.RandomGenerator.LeapableGenerator.leapDistance.

Returns the distance by which the leap() method will leap forward within the state cycle of this generator object.

Annotations

@Override

nextLong back to summary

nextLong	back to summary
public long nextLong() Implements java.util.random.RandomGenerator.nextLong. Doc from java.util.random.RandomGenerator.nextLong. Returns a pseudorandomly chosen `long` value. Annotations @Override

public long nextLong()

Implements java.util.random.RandomGenerator.nextLong.

Doc from java.util.random.RandomGenerator.nextLong.

Returns a pseudorandomly chosen long value.

Annotations

@Override

public final Class Xoroshiro128PlusPlus

Field Summary

Constructor Summary

Method Summary

Field Detail

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Method Detail