Module java.base
Package java.util

Class SplittableRandom

java.lang.Object
java.util.SplittableRandom
All Implemented Interfaces:
RandomGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator
public final class SplittableRandom extends Object implements RandomGenerator, RandomGenerator.SplittableGenerator
A generator of uniform pseudorandom values (with period 264) applicable for use in (among other contexts) isolated parallel computations that may generate subtasks. Class SplittableRandom supports methods for producing pseudorandom numbers of type int, long, and double with similar usages as for class Random but differs in the following ways:
  • Series of generated values pass the DieHarder suite testing independence and uniformity properties of random number generators. (Most recently validated with version 3.31.1.) These tests validate only the methods for certain types and ranges, but similar properties are expected to hold, at least approximately, for others as well. The period (length of any series of generated values before it repeats) is 264.
  • Method split() constructs and returns a new SplittableRandom instance that shares no mutable state with the current instance. However, with very high probability, the values collectively generated by the two objects have the same statistical properties as if the same quantity of values were generated by a single thread using a single SplittableRandom object.
  • Instances of SplittableRandom are not thread-safe. They are designed to be split, not shared, across threads. For example, a fork/join-style computation using random numbers might include a construction of the form new Subtask(aSplittableRandom.split()).fork().
  • This class provides additional methods for generating random streams, that employ the above techniques when used in stream.parallel() mode.

Instances of SplittableRandom are not cryptographically secure. Consider instead using SecureRandom in security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless the system property java.util.secureRandomSeed is set to true.

Since:
1.8

  • Constructor Details

    • SplittableRandom

      public SplittableRandom(long seed)
      Creates a new SplittableRandom instance using the specified initial seed. SplittableRandom instances created with the same seed in the same program generate identical sequences of values.
      Parameters:
      seed - the initial seed

    • SplittableRandom

      public SplittableRandom()
      Creates a new SplittableRandom instance that is likely to generate sequences of values that are statistically independent of those of any other instances in the current program; and may, and typically does, vary across program invocations.

  • Method Details

    • split

      public SplittableRandom split()
      Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance. However, with very high probability, the set of values collectively generated by the two objects has the same statistical properties as if the same quantity of values were generated by a single thread using a single SplittableRandom object. Either or both of the two objects may be further split using the split() method, and the same expected statistical properties apply to the entire set of generators constructed by such recursive splitting.
      Specified by:
      split in interface RandomGenerator.SplittableGenerator
      Returns:
      the new SplittableRandom instance

    • split

      public SplittableRandom split(RandomGenerator.SplittableGenerator source)
      Returns a new pseudorandom number generator, split off from this one, that implements the RandomGenerator and RandomGenerator.SplittableGenerator interfaces.
      Specified by:
      split in interface RandomGenerator.SplittableGenerator
      Parameters:
      source - a RandomGenerator.SplittableGenerator instance to be used instead of this one as a source of pseudorandom bits used to initialize the state of the new ones.
      Returns:
      an object that implements the RandomGenerator and RandomGenerator.SplittableGenerator interfaces
      Throws:
      NullPointerException - if source is null
      Since:
      17

    • nextLong

      public long nextLong()
      Description copied from interface: RandomGenerator
      Returns a pseudorandomly chosen long value.
      Specified by:
      nextLong in interface RandomGenerator
      Returns:
      a pseudorandomly chosen long value

    • nextBytes

      public void nextBytes(byte[] bytes)
      Fills a user-supplied byte array with generated byte values pseudorandomly chosen uniformly from the range of values between -128 (inclusive) and 127 (inclusive).
      Specified by:
      nextBytes in interface RandomGenerator
      Parameters:
      bytes - the byte array to fill with pseudorandom bytes
      Throws:
      NullPointerException - if bytes is null
      Since:
      10

    • splits

      public Stream<RandomGenerator.SplittableGenerator> splits()
      Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator.SplittableGenerator interface.

      This pseudorandom number generator may be used as a source of pseudorandom bits used to initialize the state the new ones.

      Specified by:
      splits in interface RandomGenerator.SplittableGenerator
      Implementation Requirements:
      The default implementation invokes splits(this).
      Returns:
      a stream of RandomGenerator.SplittableGenerator objects
      Since:
      17

    • splits

      public Stream<RandomGenerator.SplittableGenerator> splits(long streamSize)
      Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator.SplittableGenerator interface.

      This pseudorandom number generator may be used as a source of pseudorandom bits used to initialize the state the new ones.

      Specified by:
      splits in interface RandomGenerator.SplittableGenerator
      Implementation Requirements:
      Parameters:
      streamSize - the number of values to generate
      Returns:
      a stream of RandomGenerator.SplittableGenerator objects
      Throws:
      IllegalArgumentException - if streamSize is less than zero
      Since:
      17

    • splits

      public Stream<RandomGenerator.SplittableGenerator> splits(RandomGenerator.SplittableGenerator source)
      Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the RandomGenerator.SplittableGenerator interface.
      Specified by:
      splits in interface RandomGenerator.SplittableGenerator
      Implementation Requirements:
      Parameters:
      source - a RandomGenerator.SplittableGenerator instance to be used instead of this one as a source of pseudorandom bits used to initialize the state of the new ones.
      Returns:
      a stream of RandomGenerator.SplittableGenerator objects
      Throws:
      NullPointerException - if source is null
      Since:
      17

    • splits

      public Stream<RandomGenerator.SplittableGenerator> splits(long streamSize, RandomGenerator.SplittableGenerator source)
      Returns a stream producing the given streamSize number of new pseudorandom number generators, each of which implements the RandomGenerator.SplittableGenerator interface.
      Specified by:
      splits in interface RandomGenerator.SplittableGenerator
      Implementation Requirements:
      Parameters:
      streamSize - the number of values to generate
      source - a RandomGenerator.SplittableGenerator instance to be used instead of this one as a source of pseudorandom bits used to initialize the state of the new ones.
      Returns:
      a stream of RandomGenerator.SplittableGenerator objects
      Throws:
      NullPointerException - if source is null
      IllegalArgumentException - if streamSize is less than zero
      Since:
      17

    • ints

      public IntStream ints(long streamSize)
      Returns a stream producing the given streamSize number of pseudorandom int values from this generator and/or one split from it.
      Specified by:
      ints in interface RandomGenerator
      Parameters:
      streamSize - the number of values to generate
      Returns:
      a stream of pseudorandom int values
      Throws:
      IllegalArgumentException - if streamSize is less than zero

    • ints

      public IntStream ints()
      Returns an effectively unlimited stream of pseudorandom int values from this generator and/or one split from it.
      Specified by:
      ints in interface RandomGenerator
      Implementation Note:
      This method is implemented to be equivalent to ints(Long.MAX_VALUE).
      Returns:
      a stream of pseudorandom int values

    • ints

      public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound)
      Returns a stream producing the given streamSize number of pseudorandom int values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      Specified by:
      ints in interface RandomGenerator
      Parameters:
      streamSize - the number of values to generate
      randomNumberOrigin - the origin (inclusive) of each random value
      randomNumberBound - the bound (exclusive) of each random value
      Returns:
      a stream of pseudorandom int values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound

    • ints

      public IntStream ints(int randomNumberOrigin, int randomNumberBound)
      Returns an effectively unlimited stream of pseudorandom int values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      Specified by:
      ints in interface RandomGenerator
      Implementation Note:
      This method is implemented to be equivalent to ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
      Parameters:
      randomNumberOrigin - the origin (inclusive) of each random value
      randomNumberBound - the bound (exclusive) of each random value
      Returns:
      a stream of pseudorandom int values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - if randomNumberOrigin is greater than or equal to randomNumberBound

    • longs

      public LongStream longs(long streamSize)
      Returns a stream producing the given streamSize number of pseudorandom long values from this generator and/or one split from it.
      Specified by:
      longs in interface RandomGenerator
      Parameters:
      streamSize - the number of values to generate
      Returns:
      a stream of pseudorandom long values
      Throws:
      IllegalArgumentException - if streamSize is less than zero

    • longs

      public LongStream longs()
      Returns an effectively unlimited stream of pseudorandom long values from this generator and/or one split from it.
      Specified by:
      longs in interface RandomGenerator
      Implementation Note:
      This method is implemented to be equivalent to longs(Long.MAX_VALUE).
      Returns:
      a stream of pseudorandom long values

    • longs

      public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound)
      Returns a stream producing the given streamSize number of pseudorandom long values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      Specified by:
      longs in interface RandomGenerator
      Parameters:
      streamSize - the number of values to generate
      randomNumberOrigin - the origin (inclusive) of each random value
      randomNumberBound - the bound (exclusive) of each random value
      Returns:
      a stream of pseudorandom long values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound

    • longs

      public LongStream longs(long randomNumberOrigin, long randomNumberBound)
      Returns an effectively unlimited stream of pseudorandom long values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      Specified by:
      longs in interface RandomGenerator
      Implementation Note:
      This method is implemented to be equivalent to longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
      Parameters:
      randomNumberOrigin - the origin (inclusive) of each random value
      randomNumberBound - the bound (exclusive) of each random value
      Returns:
      a stream of pseudorandom long values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - if randomNumberOrigin is greater than or equal to randomNumberBound

    • doubles

      public DoubleStream doubles(long streamSize)
      Returns a stream producing the given streamSize number of pseudorandom double values from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).
      Specified by:
      doubles in interface RandomGenerator
      Parameters:
      streamSize - the number of values to generate
      Returns:
      a stream of double values
      Throws:
      IllegalArgumentException - if streamSize is less than zero

    • doubles

      public DoubleStream doubles()
      Returns an effectively unlimited stream of pseudorandom double values from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).
      Specified by:
      doubles in interface RandomGenerator
      Implementation Note:
      This method is implemented to be equivalent to doubles(Long.MAX_VALUE).
      Returns:
      a stream of pseudorandom double values

    • doubles

      public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)
      Returns a stream producing the given streamSize number of pseudorandom double values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      Specified by:
      doubles in interface RandomGenerator
      Parameters:
      streamSize - the number of values to generate
      randomNumberOrigin - the origin (inclusive) of each random value
      randomNumberBound - the bound (exclusive) of each random value
      Returns:
      a stream of pseudorandom double values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound

    • doubles

      public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
      Returns an effectively unlimited stream of pseudorandom double values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).
      Specified by:
      doubles in interface RandomGenerator
      Implementation Note:
      This method is implemented to be equivalent to doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
      Parameters:
      randomNumberOrigin - the origin (inclusive) of each random value
      randomNumberBound - the bound (exclusive) of each random value
      Returns:
      a stream of pseudorandom double values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - if randomNumberOrigin is greater than or equal to randomNumberBound