Module java.base
Package java.util.random

Interface RandomGenerator.ArbitrarilyJumpableGenerator

All Superinterfaces:
RandomGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.StreamableGenerator
Enclosing interface:
RandomGenerator
public static interface RandomGenerator.ArbitrarilyJumpableGenerator extends RandomGenerator.LeapableGenerator
This interface is designed to provide a common protocol for objects that generate sequences of pseudorandom values and can easily jump forward, by an arbitrary amount, to a distant point in the state cycle.

Ideally, all RandomGenerator.ArbitrarilyJumpableGenerator objects produced by iterative jumping from a single original RandomGenerator.ArbitrarilyJumpableGenerator object are statistically independent of one another and individually uniform, provided that they do not traverse overlapping portions of the state cycle. 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 the jump distance specified. Implementors are advised to use algorithms whose period is at least 2127.

For many applications, it suffices to jump forward by a power of two or some small multiple of a power of two, but this power of two may not be representable as a long value. To avoid the use of BigInteger values as jump distances, double values are used instead.

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.ArbitrarilyJumpableGenerator object, call its jump() method exactly once, and then parcel out generators from the resulting stream, one to each thread. However, each generator produced also has type RandomGenerator.ArbitrarilyJumpableGenerator; with care, different jump distances can be used to traverse the entire state cycle in various ways.

Objects that implement RandomGenerator.ArbitrarilyJumpableGenerator 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.ArbitrarilyJumpableGenerator of(String name)
      Returns an instance of RandomGenerator.ArbitrarilyJumpableGenerator that utilizes the name algorithm.
      Parameters:
      name - Name of random number generator algorithm
      Returns:
      An instance of RandomGenerator.ArbitrarilyJumpableGenerator
      Throws:
      NullPointerException - if name is null
      IllegalArgumentException - if the named algorithm is not found

    • copy

      RandomGenerator.ArbitrarilyJumpableGenerator 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
      Specified by:
      copy in interface RandomGenerator.LeapableGenerator
      Returns:
      a new object that is a copy of this generator

    • jumpPowerOfTwo

      void jumpPowerOfTwo(int logDistance)
      Alter the state of this pseudorandom number generator so as to jump forward a distance equal to 2logDistance within its state cycle.
      Parameters:
      logDistance - the base-2 logarithm of the distance to jump forward within the state cycle
      Throws:
      IllegalArgumentException - if logDistance is 2logDistance is greater than the period of this generator

    • jump

      void jump(double distance)
      Alter the state of this pseudorandom number generator so as to jump forward a specified distance within its state cycle.
      Parameters:
      distance - the distance to jump forward within the state cycle
      Throws:
      IllegalArgumentException - if distance is not greater than or equal to 0.0, or is greater than the period of this generator

    • jump

      default 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. The distance used is that returned by method jumpDistance().
      Specified by:
      jump in interface RandomGenerator.JumpableGenerator
      Implementation Requirements:
      The default implementation invokes jump(jumpDistance()).

    • jumps

      default Stream<RandomGenerator.ArbitrarilyJumpableGenerator> jumps(double distance)
      Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator.ArbitrarilyJumpableGenerator interface, produced by jumping copies of this generator by different integer multiples of the specified jump distance.
      Implementation Requirements:
      The default implementation is equivalent to jumps (Long.MAX_VALUE).
      Parameters:
      distance - a distance to jump forward within the state cycle
      Returns:
      a stream of objects that implement the RandomGenerator interface
      Throws:
      IllegalArgumentException - if distance is not greater than or equal to 0.0, or is greater than the period of this generator

    • jumps

      default Stream<RandomGenerator.ArbitrarilyJumpableGenerator> jumps(long streamSize, double distance)
      Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator.ArbitrarilyJumpableGenerator interface, produced by jumping copies of this generator by different integer multiples of the specified jump distance.
      Implementation Requirements:
      The default implementation is equivalent to jumps(distance).limit(streamSize).
      Parameters:
      streamSize - the number of generators to generate
      distance - a distance to jump forward within the state cycle
      Returns:
      a stream of objects that implement the RandomGenerator interface
      Throws:
      IllegalArgumentException - if streamSize is less than zero or if distance is not greater than or equal to 0.0, or is greater than the period of this generator

    • leap

      default void leap()
      Alter the state of this pseudorandom number generator so as to jump forward a very large, fixed distance (typically 2128 or more) within its state cycle. The distance used is that returned by method leapDistance().
      Specified by:
      leap in interface RandomGenerator.LeapableGenerator

    • copyAndJump

      default RandomGenerator.ArbitrarilyJumpableGenerator copyAndJump(double distance)
      Copy this generator, jump this generator forward, then return the copy.
      Implementation Requirements:
      The default implementation copies this, jumps(distance) and then returns the copy.
      Parameters:
      distance - a distance to jump forward within the state cycle
      Returns:
      a copy of this generator object before the jump occurred
      Throws:
      IllegalArgumentException - if distance is not greater than or equal to 0.0, or is greater than the period of this generator