Class SplittableRandom

java.lang.Object
java.util.SplittableRandom
All Implemented Interfaces:
RandomGenerator,RandomGenerator.SplittableGenerator,RandomGenerator.StreamableGenerator
public final classSplittableRandomextendsObjectimplementsRandomGenerator,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. ClassSplittableRandom supports methods for producing pseudorandom numbers of typeint,long, anddouble with similar usages as for classRandom 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. Theperiod (length of any series of generated values before it repeats) is 264.
  • Methodsplit() 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 arenot thread-safe. They are designed to be split, not shared, across threads. For example, afork/join-style computation using random numbers might include a construction of the formnew 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 ofSplittableRandom are not cryptographically secure. Consider instead usingSecureRandom in security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless thesystem propertyjava.util.secureRandomSeed is set totrue.

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 thesplit() 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

      Returns a new pseudorandom number generator, split off from this one, that implements theRandomGenerator andRandomGenerator.SplittableGenerator interfaces.
      Specified by:
      split in interface RandomGenerator.SplittableGenerator
      Parameters:
      source - aRandomGenerator.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 theRandomGenerator andRandomGenerator.SplittableGenerator interfaces
      Throws:
      NullPointerException - if source is null
      Since:
      17

    • nextLong

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

      Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements theRandomGenerator.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 invokessplits(this).
      Returns:
      a stream ofRandomGenerator.SplittableGenerator objects
      Since:
      17

    • splits

      public Stream<RandomGenerator.SplittableGenerator> splits(long streamSize)
      Returns a stream producing the givenstreamSize number of new pseudorandom number generators, each of which implements theRandomGenerator.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 ofRandomGenerator.SplittableGenerator objects
      Throws:
      IllegalArgumentException - ifstreamSize is less than zero
      Since:
      17

    • splits

      Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements theRandomGenerator.SplittableGenerator interface.
      Specified by:
      splits in interface RandomGenerator.SplittableGenerator
      Implementation Requirements:
      Parameters:
      source - aRandomGenerator.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 ofRandomGenerator.SplittableGenerator objects
      Throws:
      NullPointerException - if source is null
      Since:
      17

    • splits

      Returns a stream producing the givenstreamSize number of new pseudorandom number generators, each of which implements theRandomGenerator.SplittableGenerator interface.
      Specified by:
      splits in interface RandomGenerator.SplittableGenerator
      Implementation Requirements:
      Parameters:
      streamSize - the number of values to generate
      source - aRandomGenerator.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 ofRandomGenerator.SplittableGenerator objects
      Throws:
      NullPointerException - if source is null
      IllegalArgumentException - ifstreamSize is less than zero
      Since:
      17

    • ints

      public IntStream ints(long streamSize)
      Returns a stream producing the givenstreamSize number of pseudorandomint 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 pseudorandomint values
      Throws:
      IllegalArgumentException - ifstreamSize is less than zero

    • ints

      public IntStream ints()
      Returns an effectively unlimited stream of pseudorandomint 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 pseudorandomint values

    • ints

      public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound)
      Returns a stream producing the givenstreamSize number of pseudorandomint 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 pseudorandomint values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - ifstreamSize is less than zero, orrandomNumberOrigin is greater than or equal torandomNumberBound

    • 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 pseudorandomint values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - ifrandomNumberOrigin is greater than or equal torandomNumberBound

    • longs

      public LongStream longs(long streamSize)
      Returns a stream producing the givenstreamSize number of pseudorandomlong 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 pseudorandomlong values
      Throws:
      IllegalArgumentException - ifstreamSize 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 pseudorandomlong values

    • longs

      public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound)
      Returns a stream producing the givenstreamSize number of pseudorandomlong 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 pseudorandomlong values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - ifstreamSize is less than zero, orrandomNumberOrigin is greater than or equal torandomNumberBound

    • 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 pseudorandomlong values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - ifrandomNumberOrigin is greater than or equal torandomNumberBound

    • doubles

      public DoubleStream doubles(long streamSize)
      Returns a stream producing the givenstreamSize number of pseudorandomdouble 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 ofdouble values
      Throws:
      IllegalArgumentException - ifstreamSize 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 pseudorandomdouble values

    • doubles

      public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)
      Returns a stream producing the givenstreamSize number of pseudorandomdouble 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 pseudorandomdouble values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - ifstreamSize is less than zero, orrandomNumberOrigin is not finite, orrandomNumberBound is not finite, orrandomNumberOrigin is greater than or equal torandomNumberBound

    • 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 pseudorandomdouble values, each with the given origin (inclusive) and bound (exclusive)
      Throws:
      IllegalArgumentException - ifrandomNumberOrigin is not finite, orrandomNumberBound is not finite, orrandomNumberOrigin is greater than or equal torandomNumberBound