Module java.base

Package java.util.random

Interface RandomGenerator.LeapableGenerator

All Superinterfaces:

RandomGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.StreamableGenerator

All Known Subinterfaces:

RandomGenerator.ArbitrarilyJumpableGenerator

Enclosing interface:

RandomGenerator

public static interface RandomGenerator.LeapableGenerator
extends RandomGenerator.JumpableGenerator

This interface is designed to provide a common protocol for objects that generate sequences of pseudorandom values and can easily not only jump but also leap forward, by a large amount (ex. 2¹²⁸), to a very distant point in the state cycle. Typically one will construct a series of RandomGenerator.LeapableGenerator objects by iterative leaping from a single original RandomGenerator.LeapableGenerator object, and then for each such object produce a subseries of objects by iterative jumping. There is little conceptual difference between leaping and jumping, but typically a leap will be a very long jump in the state cycle (perhaps distance 2¹²⁸ or so).

Ideally, all RandomGenerator.LeapableGenerator objects produced by iterative leaping and jumping from a single original RandomGenerator.LeapableGenerator 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 leaps method is used to produce (by jumping) a number of objects no larger than 2⁶⁴. Implementors are advised to use algorithms whose period is at least 2¹⁹¹.

Methods are provided to perform a single leap operation and also to produce a stream of generators produced from the original by iterative copying and leaping of internal state. The generators produced must implement the RandomGenerator.JumpableGenerator interface but need not also implement the RandomGenerator.LeapableGenerator interface. A typical strategy for a multithreaded application is to create a single RandomGenerator.LeapableGenerator object, calls its leaps method exactly once, and then parcel out generators from the resulting stream, one to each thread. Then the jump() method of each such generator be called to produce a substream of generator objects.

Objects that implement RandomGenerator.LeapableGenerator 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.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).
default RandomGenerator.JumpableGenerator	copyAndLeap()	Copy this generator, leap this generator forward, then return the copy.
void	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.
double	leapDistance()	Returns the distance by which the leap() method will leap forward within the state cycle of this generator object.
default Stream<RandomGenerator.JumpableGenerator>	leaps()	Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator.JumpableGenerator interface.
default Stream<RandomGenerator.JumpableGenerator>	leaps(long streamSize)	Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator.JumpableGenerator interface.
static RandomGenerator.LeapableGenerator	of(String name)	Returns an instance of RandomGenerator.LeapableGenerator that utilizes the name algorithm.

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

Methods declared in interface java.util.random.RandomGenerator.JumpableGenerator

copyAndJump, jump, jumpDistance, jumps, jumps, rngs, rngs

Method Details

of

static RandomGenerator.LeapableGenerator of(String name)

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

Parameters:

name - Name of random number generator algorithm

Returns:

An instance of RandomGenerator.LeapableGenerator

Throws:

NullPointerException - if name is null

IllegalArgumentException - if the named algorithm is not found

copy

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).

Specified by:

copy in interface RandomGenerator.JumpableGenerator

Returns:

a new object that is a copy of this generator

leap

void 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.

leapDistance

double leapDistance()

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

Returns:

the default leap distance (as a double value)

leaps

default Stream<RandomGenerator.JumpableGenerator> leaps()

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

Implementation Requirements:

The default implementation produces a sequential stream that repeatedly calls copy() and leap() 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 leaps (Long.MAX_VALUE).

Returns:

a stream of objects that implement the RandomGenerator.JumpableGenerator interface

leaps

default Stream<RandomGenerator.JumpableGenerator> leaps(long streamSize)

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

Implementation Requirements:

The default implementation produces a sequential stream that repeatedly calls copy() and leap() 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.JumpableGenerator interface

Throws:

IllegalArgumentException - if streamSize is less than zero

copyAndLeap

default RandomGenerator.JumpableGenerator copyAndLeap()

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

Implementation Requirements:

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

Returns:

a copy of this generator object before the leap occurred