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.

  • 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