Module java.base

Package java.util.random

Interface RandomGenerator.JumpableGenerator

All Superinterfaces:

RandomGenerator, RandomGenerator.StreamableGenerator

All Known Subinterfaces:

RandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.LeapableGenerator

Enclosing interface:

RandomGenerator

public static interface RandomGenerator.JumpableGenerator
extends RandomGenerator.StreamableGenerator

This interface is designed to provide a common protocol for objects that generate pseudorandom values and can easily jump forward, by a moderate amount (ex. 2⁶⁴) to a distant point in the state cycle.

Ideally, all RandomGenerator.JumpableGenerator objects produced by iterative jumping from a single original RandomGenerator.JumpableGenerator object are statistically independent of one another and individually uniform. In practice, one must settle for some approximation to independence and uniformity. In particular, a specific implementation may assume that each generator in a stream produced by the jump() method is used to produce a number of values no larger than either 2⁶⁴ or the square root of its period. Implementors are advised to use algorithms whose period is at least 2¹²⁷.

Methods are provided to perform a single jump operation and also to produce a stream of generators produced from the original by iterative copying and jumping of internal state. A typical strategy for a multithreaded application is to create a single RandomGenerator.JumpableGenerator object, calls its jump() method exactly once, and then parcel out generators from the resulting stream, one to each thread. It is generally not a good idea to call jump() on a generator that was itself produced by the jump() method, because the result may be a generator identical to another generator already produce by that call to the jump() method. For this reason, the return type of the jumps() method is Stream<RandomGenerator> rather than Stream<RandomGenerator.JumpableGenerator>, even though the actual generator objects in that stream likely do also implement the RandomGenerator.JumpableGenerator interface.

Objects that implement RandomGenerator.JumpableGenerator are typically not cryptographically secure. Consider instead using SecureRandom to get a cryptographically secure pseudo-random number generator for use by security-sensitive applications.

Nested Class Summary

Nested classes/interfaces declared in interface java.util.random.RandomGenerator

RandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator

Method Summary

Modifier and Type	Method	Description
RandomGenerator.JumpableGenerator	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).
default RandomGenerator	copyAndJump()	Copy this generator, jump this generator forward, then return the copy.
void	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.
double	jumpDistance()	Returns the distance by which the jump() method will jump forward within the state cycle of this generator object.
default Stream<RandomGenerator>	jumps()	Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator interface.
default Stream<RandomGenerator>	jumps(long streamSize)	Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator interface.
static RandomGenerator.JumpableGenerator	of(String name)	Returns an instance of RandomGenerator.JumpableGenerator that utilizes the name algorithm.
default Stream<RandomGenerator>	rngs()	Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator interface.
default Stream<RandomGenerator>	rngs(long streamSize)	Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator interface.

Methods declared in interface java.util.random.RandomGenerator

doubles, doubles, doubles, doubles, equiDoubles, ints, ints, ints, ints, isDeprecated, longs, longs, longs, longs, nextBoolean, nextBytes, nextDouble, nextDouble, nextDouble, nextExponential, nextFloat, nextFloat, nextFloat, nextGaussian, nextGaussian, nextInt, nextInt, nextInt, nextLong, nextLong, nextLong

Method Details

of

static RandomGenerator.JumpableGenerator of(String name)

Returns an instance of RandomGenerator.JumpableGenerator that utilizes the name algorithm.

Parameters:

name - Name of random number generator algorithm

Returns:

An instance of RandomGenerator.JumpableGenerator

Throws:

NullPointerException - if name is null

IllegalArgumentException - if the named algorithm is not found

copy

RandomGenerator.JumpableGenerator 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).

Returns:

a new object that is a copy of this generator

jump

void 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.

jumpDistance

double jumpDistance()

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

Returns:

the default jump distance (as a double value)

jumps

default Stream<RandomGenerator> jumps()

Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator interface.

Implementation Requirements:

The default implementation produces a sequential stream that repeatedly calls copy() and jump() on this generator, and the copies become the generators produced by the stream.

Implementation Note:

It is permitted to implement this method in a manner equivalent to jumps (Long.MAX_VALUE).

Returns:

a stream of objects that implement the RandomGenerator interface

jumps

default Stream<RandomGenerator> jumps(long streamSize)

Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator interface.

Implementation Requirements:

The default implementation produces a sequential stream that repeatedly calls copy() and jump() on this generator, and the copies become the generators produced by the stream.

Parameters:

streamSize - the number of generators to generate

Returns:

a stream of objects that implement the RandomGenerator interface

Throws:

IllegalArgumentException - if streamSize is less than zero

rngs

default Stream<RandomGenerator> rngs()

Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator interface. Ideally the generators in the stream will appear to be statistically independent.

Specified by:

rngs in interface RandomGenerator.StreamableGenerator

Implementation Requirements:

The default implementation calls jumps().

Returns:

a stream of objects that implement the RandomGenerator interface

rngs

default Stream<RandomGenerator> rngs(long streamSize)

Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator interface. Ideally the generators in the stream will appear to be statistically independent.

Specified by:

rngs in interface RandomGenerator.StreamableGenerator

Implementation Requirements:

The default implementation calls jumps(streamSize).

Parameters:

streamSize - the number of generators to generate

Returns:

a stream of objects that implement the RandomGenerator interface

Throws:

IllegalArgumentException - if streamSize is less than zero

copyAndJump

default RandomGenerator copyAndJump()

Copy this generator, jump this generator forward, then return the copy.

Implementation Requirements:

The default implementation copies this, jumps and then returns the copy.

Returns:

a copy of this generator object before the jump occurred