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 singleSplittableRandom
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 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 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
ConstructorDescriptionCreates 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 TypeMethodDescriptiondoubles()
Returns an effectively unlimited stream of pseudorandomdouble
values from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).doubles
(double randomNumberOrigin, double randomNumberBound) Returns an effectively unlimited stream of pseudorandomdouble
values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).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).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).ints()
Returns an effectively unlimited stream of pseudorandomint
values from this generator and/or one split from it.ints
(int randomNumberOrigin, int randomNumberBound) Returns an effectively unlimited stream of pseudorandomint
values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).ints
(long streamSize) Returns a stream producing the givenstreamSize
number of pseudorandomint
values from this generator and/or one split from it.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).longs()
Returns an effectively unlimited stream of pseudorandomlong
values from this generator and/or one split from it.longs
(long streamSize) Returns a stream producing the givenstreamSize
number of pseudorandomlong
values from this generator and/or one split from it.longs
(long randomNumberOrigin, long randomNumberBound) Returns an effectively unlimited stream of pseudorandomlong
values from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).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).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 chosenlong
value.split()
Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance.Returns a new pseudorandom number generator, split off from this one, that implements theRandomGenerator
andRandomGenerator.SplittableGenerator
interfaces.splits()
Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements theRandomGenerator.SplittableGenerator
interface.splits
(long streamSize) Returns a stream producing the givenstreamSize
number of new pseudorandom number generators, each of which implements theRandomGenerator.SplittableGenerator
interface.splits
(long streamSize, RandomGenerator.SplittableGenerator source) Returns a stream producing the givenstreamSize
number of new pseudorandom number generators, each of which implements theRandomGenerator.SplittableGenerator
interface.Returns an effectively unlimited stream of new pseudorandom number generators, each of which implements theRandomGenerator.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
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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
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 interfaceRandomGenerator.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 interfaceRandomGenerator.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 the
RandomGenerator
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 interfaceRandomGenerator
- 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 interfaceRandomGenerator
- 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 interfaceRandomGenerator.SplittableGenerator
- Implementation Requirements:
- The default implementation invokes
splits(this)
. - Returns:
- a stream of
RandomGenerator.SplittableGenerator
objects - Since:
- 17
-
splits
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 interfaceRandomGenerator.SplittableGenerator
- Implementation Requirements:
- Parameters:
streamSize
- the number of values to generate- Returns:
- a stream of
RandomGenerator.SplittableGenerator
objects - Throws:
IllegalArgumentException
- ifstreamSize
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 theRandomGenerator.SplittableGenerator
interface.- Specified by:
splits
in interfaceRandomGenerator.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 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 givenstreamSize
number of new pseudorandom number generators, each of which implements theRandomGenerator.SplittableGenerator
interface.- Specified by:
splits
in interfaceRandomGenerator.SplittableGenerator
- Implementation Requirements:
- Parameters:
streamSize
- the number of values to generatesource
- 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 of
RandomGenerator.SplittableGenerator
objects - Throws:
NullPointerException
- if source is nullIllegalArgumentException
- ifstreamSize
is less than zero- Since:
- 17
-
ints
Returns a stream producing the givenstreamSize
number of pseudorandomint
values from this generator and/or one split from it.- Specified by:
ints
in interfaceRandomGenerator
- Parameters:
streamSize
- the number of values to generate- Returns:
- a stream of pseudorandom
int
values - Throws:
IllegalArgumentException
- ifstreamSize
is less than zero
-
ints
Returns an effectively unlimited stream of pseudorandomint
values from this generator and/or one split from it.- Specified by:
ints
in interfaceRandomGenerator
- Implementation Note:
- This method is implemented to be equivalent to
ints(Long.MAX_VALUE)
. - Returns:
- a stream of pseudorandom
int
values
-
ints
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 interfaceRandomGenerator
- Parameters:
streamSize
- the number of values to generaterandomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- 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
- ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
-
ints
Returns an effectively unlimited stream 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 interfaceRandomGenerator
- Implementation Note:
- This method is implemented to be equivalent to
ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
. - Parameters:
randomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- 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
- ifrandomNumberOrigin
is greater than or equal torandomNumberBound
-
longs
Returns a stream producing the givenstreamSize
number of pseudorandomlong
values from this generator and/or one split from it.- Specified by:
longs
in interfaceRandomGenerator
- Parameters:
streamSize
- the number of values to generate- Returns:
- a stream of pseudorandom
long
values - Throws:
IllegalArgumentException
- ifstreamSize
is less than zero
-
longs
Returns an effectively unlimited stream of pseudorandomlong
values from this generator and/or one split from it.- Specified by:
longs
in interfaceRandomGenerator
- Implementation Note:
- This method is implemented to be equivalent to
longs(Long.MAX_VALUE)
. - Returns:
- a stream of pseudorandom
long
values
-
longs
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 interfaceRandomGenerator
- Parameters:
streamSize
- the number of values to generaterandomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- 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
- ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
-
longs
Returns an effectively unlimited stream 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 interfaceRandomGenerator
- Implementation Note:
- This method is implemented to be equivalent to
longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
. - Parameters:
randomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- 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
- ifrandomNumberOrigin
is greater than or equal torandomNumberBound
-
doubles
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 interfaceRandomGenerator
- Parameters:
streamSize
- the number of values to generate- Returns:
- a stream of
double
values - Throws:
IllegalArgumentException
- ifstreamSize
is less than zero
-
doubles
Returns an effectively unlimited stream 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 interfaceRandomGenerator
- Implementation Note:
- This method is implemented to be equivalent to
doubles(Long.MAX_VALUE)
. - Returns:
- a stream of pseudorandom
double
values
-
doubles
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 interfaceRandomGenerator
- Parameters:
streamSize
- the number of values to generaterandomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- 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
- ifstreamSize
is less than zero, orrandomNumberOrigin
is not finite, orrandomNumberBound
is not finite, orrandomNumberOrigin
is greater than or equal torandomNumberBound
-
doubles
Returns an effectively unlimited stream 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 interfaceRandomGenerator
- Implementation Note:
- This method is implemented to be equivalent to
doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
. - Parameters:
randomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- 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
- ifrandomNumberOrigin
is not finite, orrandomNumberBound
is not finite, orrandomNumberOrigin
is greater than or equal torandomNumberBound
-