SplittableRandom

SplittableRandom | API reference | Android Developers

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.

Summary

Public constructors
`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.

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(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, 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()` 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

From class java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface java.util.random.RandomGenerator

`default DoubleStream`	`doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default DoubleStream`	`doubles(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `double` values.
`default DoubleStream`	`doubles()` Returns an effectively unlimited stream of pseudorandomly chosen `double` values.
`default DoubleStream`	`doubles(double randomNumberOrigin, double randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `double` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`static RandomGenerator`	`getDefault()` Returns a `RandomGenerator` meeting the minimal requirement of having an algorithm whose state bits are greater than or equal 64.
`default IntStream`	`ints(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values.
`default IntStream`	`ints(int randomNumberOrigin, int randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default IntStream`	`ints()` Returns an effectively unlimited stream of pseudorandomly chosen `int` values.
`default IntStream`	`ints(long streamSize, int randomNumberOrigin, int randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `int` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default boolean`	`isDeprecated()` Return true if the implementation of RandomGenerator (algorithm) has been marked for deprecation.
`default LongStream`	`longs(long streamSize)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values.
`default LongStream`	`longs()` Returns an effectively unlimited stream of pseudorandomly chosen `long` values.
`default LongStream`	`longs(long randomNumberOrigin, long randomNumberBound)` Returns an effectively unlimited stream of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default LongStream`	`longs(long streamSize, long randomNumberOrigin, long randomNumberBound)` Returns a stream producing the given `streamSize` number of pseudorandomly chosen `long` values, where each value is between the specified origin (inclusive) and the specified bound (exclusive).
`default boolean`	`nextBoolean()` Returns a pseudorandomly chosen `boolean` value.
`default 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).
`default double`	`nextDouble()` Returns a pseudorandom `double` value between zero (inclusive) and one (exclusive).
`default double`	`nextDouble(double bound)` Returns a pseudorandomly chosen `double` value between zero (inclusive) and the specified bound (exclusive).
`default double`	`nextDouble(double origin, double bound)` Returns a pseudorandomly chosen `double` value between the specified origin (inclusive) and the specified bound (exclusive).
`default double`	`nextExponential()` Returns a nonnegative `double` value pseudorandomly chosen from an exponential distribution whose mean is 1.
`default float`	`nextFloat(float origin, float bound)` Returns a pseudorandomly chosen `float` value between the specified origin (inclusive) and the specified bound (exclusive).
`default float`	`nextFloat()` Returns a pseudorandom `float` value between zero (inclusive) and one (exclusive).
`default float`	`nextFloat(float bound)` Returns a pseudorandomly chosen `float` value between zero (inclusive) and the specified bound (exclusive).
`default double`	`nextGaussian(double mean, double stddev)` Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution with a mean and standard deviation specified by the arguments.
`default double`	`nextGaussian()` Returns a `double` value pseudorandomly chosen from a Gaussian (normal) distribution whose mean is 0 and whose standard deviation is 1.
`default int`	`nextInt(int origin, int bound)` Returns a pseudorandomly chosen `int` value between the specified origin (inclusive) and the specified bound (exclusive).
`default int`	`nextInt()` Returns a pseudorandomly chosen `int` value.
`default int`	`nextInt(int bound)` Returns a pseudorandomly chosen `int` value between zero (inclusive) and the specified bound (exclusive).
`default long`	`nextLong(long origin, long bound)` Returns a pseudorandomly chosen `long` value between the specified origin (inclusive) and the specified bound (exclusive).
`default long`	`nextLong(long bound)` Returns a pseudorandomly chosen `long` value between zero (inclusive) and the specified bound (exclusive).
`abstract long`	`nextLong()` Returns a pseudorandomly chosen `long` value.
`static RandomGenerator`	`of(String name)` Returns an instance of `RandomGenerator` that utilizes the `name` algorithm.

From interface java.util.random.RandomGenerator.SplittableGenerator

`static RandomGenerator.SplittableGenerator`	`of(String name)` Returns an instance of `SplittableGenerator` that utilizes the `name` algorithm.
`default Stream<RandomGenerator>`	`rngs(long streamSize)` Returns a stream producing the given `streamSize` number of new pseudorandom number generators, each of which implements the `RandomGenerator` interface.
`default Stream<RandomGenerator>`	`rngs()` Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the `RandomGenerator` interface.
`abstract RandomGenerator.SplittableGenerator`	`split(RandomGenerator.SplittableGenerator source)` Returns a new pseudorandom number generator, split off from this one, that implements the `RandomGenerator` and `SplittableGenerator` interfaces.
`abstract RandomGenerator.SplittableGenerator`	`split()` Returns a new pseudorandom number generator, split off from this one, that implements the `RandomGenerator` and `SplittableGenerator` interfaces.
`default Stream<RandomGenerator.SplittableGenerator>`	`splits()` Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the `SplittableGenerator` interface.
`abstract 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.
`abstract 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.
`abstract Stream<RandomGenerator.SplittableGenerator>`	`splits(RandomGenerator.SplittableGenerator source)` Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements the `SplittableGenerator` interface.

From interface java.util.random.RandomGenerator.StreamableGenerator

`static RandomGenerator.StreamableGenerator`	`of(String name)` Returns an instance of `StreamableGenerator` that utilizes the `name` algorithm.
`default Stream<RandomGenerator>`	`rngs(long streamSize)` Returns an effectively unlimited stream of objects, each of which implements the `RandomGenerator` interface.
`abstract Stream<RandomGenerator>`	`rngs()` Returns an effectively unlimited stream of objects, each of which implements the `RandomGenerator` interface.

Public constructors

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.

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`	`long`: the initial seed

Public methods

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).

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

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

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

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

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

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

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

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

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

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

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

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

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

public int nextInt ()

Returns a pseudorandomly chosen int value.

Returns
`int`	a pseudorandomly chosen `int` value

nextLong

public long nextLong ()

Returns a pseudorandomly chosen long value.

Returns
`long`	a pseudorandomly chosen `long` value

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.

Returns
`SplittableRandom`	the new SplittableRandom instance