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

- ## Nested Class Summary

  ## Nested classes/interfaces declared in interface java.util.random.RandomGenerator

  `RandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `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.
  `SplittableRandom(long seed)`
  Creates a new SplittableRandom instance using the specified initial seed.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `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).
  `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).
  `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).
  `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).
  `IntStream`
  `ints()`
  Returns an effectively unlimited stream of pseudorandom `int` values from this generator and/or one split from it.
  `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).
  `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.
  `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).
  `LongStream`
  `longs()`
  Returns an effectively unlimited stream of pseudorandom `long` values from this generator and/or one split from it.
  `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.
  `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).
  `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).
  `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).
  `long`
  `nextLong()`
  Returns a pseudorandomly chosen `long` value.
  `SplittableRandom`
  `split()`
  Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance.
  `SplittableRandom`
  `split(RandomGenerator.SplittableGenerator source)`
  Returns a new pseudorandom number generator, split off from this one, that implements the `RandomGenerator` and `RandomGenerator.SplittableGenerator` interfaces.
  `Stream<RandomGenerator.SplittableGenerator>`
  `splits()`
  Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the `RandomGenerator.SplittableGenerator` interface.
  `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.
  `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.
  `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.

  ### Methods declared in class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

  ### Methods declared in interface java.util.random.RandomGenerator

  `isDeprecated, nextBoolean, nextDouble, nextDouble, nextDouble, nextExponential, nextFloat, nextFloat, nextFloat, nextGaussian, nextGaussian, nextInt, nextInt, nextInt, nextLong, nextLong`

  ### Methods declared in interface java.util.random.RandomGenerator.SplittableGenerator

  `rngs, rngs`

- ## 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 not finite, or `randomNumberBound` is not finite, 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 not finite, or `randomNumberBound` is not finite, or `randomNumberOrigin` is greater than or equal to `randomNumberBound`