java.lang.Object
java.util.SplittableRandom
public final class SplittableRandom extends Object
A generator of uniform pseudorandom values 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 at least 2^{64}.
 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 threadsafe.
They are designed to be split, not shared, across threads. For
example, a
fork/joinstyle
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 securitysensitive applications. Additionally,
defaultconstructed instances do not use a cryptographically random
seed unless the system property
java.util.secureRandomSeed
is set to true
.
 Since:
 1.8

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 pseudorandomdouble
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 pseudorandomdouble
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 givenstreamSize
number of pseudorandomdouble
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 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).IntStream
ints()
Returns an effectively unlimited stream of pseudorandomint
values from this generator and/or one split from it.IntStream
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).IntStream
ints(long streamSize)
Returns a stream producing the givenstreamSize
number of pseudorandomint
values from this generator and/or one split from it.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).LongStream
longs()
Returns an effectively unlimited stream of pseudorandomlong
values from this generator and/or one split from it.LongStream
longs(long streamSize)
Returns a stream producing the givenstreamSize
number of pseudorandomlong
values from this generator and/or one split from it.LongStream
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).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).boolean
nextBoolean()
Returns a pseudorandomboolean
value.void
nextBytes(byte[] bytes)
Fills a usersupplied byte array with generated pseudorandom bytes.double
nextDouble()
Returns a pseudorandomdouble
value between zero (inclusive) and one (exclusive).double
nextDouble(double bound)
Returns a pseudorandomdouble
value between 0.0 (inclusive) and the specified bound (exclusive).double
nextDouble(double origin, double bound)
Returns a pseudorandomdouble
value between the specified origin (inclusive) and bound (exclusive).int
nextInt()
Returns a pseudorandomint
value.int
nextInt(int bound)
Returns a pseudorandomint
value between zero (inclusive) and the specified bound (exclusive).int
nextInt(int origin, int bound)
Returns a pseudorandomint
value between the specified origin (inclusive) and the specified bound (exclusive).long
nextLong()
Returns a pseudorandomlong
value.long
nextLong(long bound)
Returns a pseudorandomlong
value between zero (inclusive) and the specified bound (exclusive).long
nextLong(long origin, long bound)
Returns a pseudorandomlong
value between the specified origin (inclusive) and the specified bound (exclusive).SplittableRandom
split()
Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance.

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. Returns:
 the new SplittableRandom instance

nextBytes
public void nextBytes(byte[] bytes)Fills a usersupplied byte array with generated pseudorandom bytes. Parameters:
bytes
 the byte array to fill with pseudorandom bytes Throws:
NullPointerException
 if bytes is null Since:
 10

nextInt
public int nextInt()Returns a pseudorandomint
value. Returns:
 a pseudorandom
int
value

nextInt
public int nextInt(int bound)Returns a pseudorandomint
value between zero (inclusive) and the specified bound (exclusive). Parameters:
bound
 the upper bound (exclusive). Must be positive. Returns:
 a pseudorandom
int
value between zero (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 ifbound
is not positive

nextInt
public int nextInt(int origin, int bound)Returns a pseudorandomint
value between the specified origin (inclusive) and the specified bound (exclusive). Parameters:
origin
 the least value returnedbound
 the upper bound (exclusive) Returns:
 a pseudorandom
int
value between the origin (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 iforigin
is greater than or equal tobound

nextLong
public long nextLong()Returns a pseudorandomlong
value. Returns:
 a pseudorandom
long
value

nextLong
public long nextLong(long bound)Returns a pseudorandomlong
value between zero (inclusive) and the specified bound (exclusive). Parameters:
bound
 the upper bound (exclusive). Must be positive. Returns:
 a pseudorandom
long
value between zero (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 ifbound
is not positive

nextLong
public long nextLong(long origin, long bound)Returns a pseudorandomlong
value between the specified origin (inclusive) and the specified bound (exclusive). Parameters:
origin
 the least value returnedbound
 the upper bound (exclusive) Returns:
 a pseudorandom
long
value between the origin (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 iforigin
is greater than or equal tobound

nextDouble
public double nextDouble()Returns a pseudorandomdouble
value between zero (inclusive) and one (exclusive). Returns:
 a pseudorandom
double
value between zero (inclusive) and one (exclusive)

nextDouble
public double nextDouble(double bound)Returns a pseudorandomdouble
value between 0.0 (inclusive) and the specified bound (exclusive). Parameters:
bound
 the upper bound (exclusive). Must be positive. Returns:
 a pseudorandom
double
value between zero (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 ifbound
is not positive

nextDouble
public double nextDouble(double origin, double bound)Returns a pseudorandomdouble
value between the specified origin (inclusive) and bound (exclusive). Parameters:
origin
 the least value returnedbound
 the upper bound (exclusive) Returns:
 a pseudorandom
double
value between the origin (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 iforigin
is greater than or equal tobound

nextBoolean
public boolean nextBoolean()Returns a pseudorandomboolean
value. Returns:
 a pseudorandom
boolean
value

ints
Returns a stream producing the givenstreamSize
number of pseudorandomint
values from this generator and/or one split from it. 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. 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). 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). 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. 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. 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). 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). 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). 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). 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). 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 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). 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 greater than or equal torandomNumberBound
