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.

  • 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