SplittableRandom

public final class SplittableRandom
extends Object implements RandomGenerator, RandomGenerator.SplittableGenerator

java.lang.Object
   ↳ java.util.SplittableRandom


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.

Summary

Public constructors

SplittableRandom(long seed)

Creates a new SplittableRandom instance using the specified initial seed.

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.

Public methods

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()

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, 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(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).

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()

Returns an effectively unlimited stream of pseudorandom int values from this generator and/or one split from it.

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).

int nextInt()

Returns a pseudorandomly chosen int value.

long nextLong()

Returns a pseudorandomly chosen long value.

SplittableRandom split(RandomGenerator.SplittableGenerator source)

Returns a new pseudorandom number generator, split off from this one, that implements the RandomGenerator and SplittableGenerator interfaces.

SplittableRandom split()

Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance.

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 SplittableGenerator interface.

Stream<RandomGenerator.SplittableGenerator> splits()

Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the 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 SplittableGenerator interface.

Stream<RandomGenerator.SplittableGenerator> splits(RandomGenerator.SplittableGenerator source)

Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the SplittableGenerator interface.

Inherited methods

Public constructors

SplittableRandom

Added in API level 24
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 long: the initial seed

SplittableRandom

Added in API level 24
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.

Public methods

doubles

Added in API level 24
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).

Parameters
streamSize long: the number of values to generate

Returns
DoubleStream a stream of double values

Throws
IllegalArgumentException if streamSize is less than zero

doubles

Added in API level 24
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).

Implementation Note:
  • This method is implemented to be equivalent to doubles(Long.MAX_VALUE).
Returns
DoubleStream a stream of pseudorandom double values

doubles

Added in API level 24
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).

Implementation Note:
  • This method is implemented to be equivalent to doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
Parameters
randomNumberOrigin double: the origin (inclusive) of each random value

randomNumberBound double: the bound (exclusive) of each random value

Returns
DoubleStream 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

doubles

Added in API level 24
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).

Parameters
streamSize long: the number of values to generate

randomNumberOrigin double: the origin (inclusive) of each random value

randomNumberBound double: the bound (exclusive) of each random value

Returns
DoubleStream 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

ints

Added in API level 24
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.

Parameters
streamSize long: the number of values to generate

Returns
IntStream a stream of pseudorandom int values

Throws
IllegalArgumentException if streamSize is less than zero

ints

Added in API level 24
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).

Parameters
streamSize long: the number of values to generate

randomNumberOrigin int: the origin (inclusive) of each random value

randomNumberBound int: the bound (exclusive) of each random value

Returns
IntStream 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

Added in API level 24
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).

Implementation Note:
  • This method is implemented to be equivalent to ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
Parameters
randomNumberOrigin int: the origin (inclusive) of each random value

randomNumberBound int: the bound (exclusive) of each random value

Returns
IntStream 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

ints

Added in API level 24
public IntStream ints ()

Returns an effectively unlimited stream of pseudorandom int values from this generator and/or one split from it.

Implementation Note:
  • This method is implemented to be equivalent to ints(Long.MAX_VALUE).
Returns
IntStream a stream of pseudorandom int values

longs

Added in API level 24
public LongStream longs ()

Returns an effectively unlimited stream of pseudorandom long values from this generator and/or one split from it.

Implementation Note:
  • This method is implemented to be equivalent to longs(Long.MAX_VALUE).
Returns
LongStream a stream of pseudorandom long values

longs

Added in API level 24
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.

Parameters
streamSize long: the number of values to generate

Returns
LongStream a stream of pseudorandom long values

Throws
IllegalArgumentException if streamSize is less than zero

longs

Added in API level 24
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).

Implementation Note:
  • This method is implemented to be equivalent to longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound).
Parameters
randomNumberOrigin long: the origin (inclusive) of each random value

randomNumberBound long: the bound (exclusive) of each random value

Returns
LongStream 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

longs

Added in API level 24
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).

Parameters
streamSize long: the number of values to generate

randomNumberOrigin long: the origin (inclusive) of each random value

randomNumberBound long: the bound (exclusive) of each random value

Returns
LongStream 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

nextBytes

Added in API level 33
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).

Parameters
bytes byte: the byte array to fill with pseudorandom bytes

Throws
NullPointerException

nextInt

Added in API level 24
public int nextInt ()

Returns a pseudorandomly chosen int value.

Returns
int a pseudorandomly chosen int value

nextLong

Added in API level 24
public long nextLong ()

Returns a pseudorandomly chosen long value.

Returns
long a pseudorandomly chosen long value

split

Added in API level 35
public SplittableRandom split (RandomGenerator.SplittableGenerator source)

Returns a new pseudorandom number generator, split off from this one, that implements the RandomGenerator and SplittableGenerator interfaces.

Parameters
source RandomGenerator.SplittableGenerator: a 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
SplittableRandom an object that implements the RandomGenerator and SplittableGenerator interfaces

Throws
NullPointerException

split

Added in API level 24
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.

Returns
SplittableRandom the new SplittableRandom instance

splits

Added in API level 35
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 SplittableGenerator interface.

Implementation Requirements:
Parameters
streamSize long: the number of values to generate

source RandomGenerator.SplittableGenerator: a 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
Stream<RandomGenerator.SplittableGenerator> a stream of SplittableGenerator objects

Throws
NullPointerException
IllegalArgumentException

splits

Added in API level 35
public Stream<RandomGenerator.SplittableGenerator> splits ()

Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the SplittableGenerator interface.

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

Implementation Requirements:
Returns
Stream<RandomGenerator.SplittableGenerator> a stream of SplittableGenerator objects

splits

Added in API level 35
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 SplittableGenerator interface.

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

Implementation Requirements:
Parameters
streamSize long: the number of values to generate

Returns
Stream<RandomGenerator.SplittableGenerator> a stream of SplittableGenerator objects

Throws
IllegalArgumentException

splits

Added in API level 35
public Stream<RandomGenerator.SplittableGenerator> splits (RandomGenerator.SplittableGenerator source)

Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the SplittableGenerator interface.

Implementation Requirements:
Parameters
source RandomGenerator.SplittableGenerator: a 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
Stream<RandomGenerator.SplittableGenerator> a stream of SplittableGenerator objects

Throws
NullPointerException