Class SplittableRandom
 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
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 
DoubleStream  doubles(double randomNumberOrigin,
double randomNumberBound)  Returns an effectively unlimited stream of pseudorandom 
DoubleStream  doubles(long streamSize)  Returns a stream producing the given 
DoubleStream  doubles(long streamSize,
double randomNumberOrigin,
double randomNumberBound)  Returns a stream producing the given 
IntStream  ints()  Returns an effectively unlimited stream of pseudorandom 
IntStream  ints(int randomNumberOrigin,
int randomNumberBound)  Returns an effectively unlimited stream of pseudorandom 
IntStream  ints(long streamSize)  Returns a stream producing the given 
IntStream  ints(long streamSize,
int randomNumberOrigin,
int randomNumberBound)  Returns a stream producing the given 
LongStream  longs()  Returns an effectively unlimited stream of pseudorandom 
LongStream  longs(long streamSize)  Returns a stream producing the given 
LongStream  longs(long randomNumberOrigin,
long randomNumberBound)  Returns an effectively unlimited stream of pseudorandom 
LongStream  longs(long streamSize,
long randomNumberOrigin,
long randomNumberBound)  Returns a stream producing the given 
boolean  nextBoolean()  Returns a pseudorandom 
void  nextBytes(byte[] bytes)  Fills a usersupplied byte array with generated pseudorandom bytes. 
double  nextDouble()  Returns a pseudorandom 
double  nextDouble(double bound)  Returns a pseudorandom 
double  nextDouble(double origin,
double bound)  Returns a pseudorandom 
int  nextInt()  Returns a pseudorandom 
int  nextInt(int bound)  Returns a pseudorandom 
int  nextInt(int origin,
int bound)  Returns a pseudorandom 
long  nextLong()  Returns a pseudorandom 
long  nextLong(long bound)  Returns a pseudorandom 
long  nextLong(long origin,
long bound)  Returns a pseudorandom 
SplittableRandom  split()  Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance. 
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Constructor Detail
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 Detail
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:
 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 pseudorandom int
value.
 Returns:
 a pseudorandom
int
value
nextInt
public int nextInt(int bound)
Returns a pseudorandom int
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 pseudorandom int
value between the specified origin (inclusive) and the specified bound (exclusive).
 Parameters:

origin
 the least value returned 
bound
 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 pseudorandom long
value.
 Returns:
 a pseudorandom
long
value
nextLong
public long nextLong(long bound)
Returns a pseudorandom long
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 pseudorandom long
value between the specified origin (inclusive) and the specified bound (exclusive).
 Parameters:

origin
 the least value returned 
bound
 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 pseudorandom double
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 pseudorandom double
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 pseudorandom double
value between the specified origin (inclusive) and bound (exclusive).
 Parameters:

origin
 the least value returned 
bound
 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 pseudorandom boolean
value.
 Returns:
 a pseudorandom
boolean
value
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
 the number of values to generate  Returns:
 a stream of pseudorandom
int
values  Throws:

IllegalArgumentException
 ifstreamSize
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.
 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).
 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
 ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
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
 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
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound
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
 the number of values to generate  Returns:
 a stream of pseudorandom
long
values  Throws:

IllegalArgumentException
 ifstreamSize
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.
 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).
 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
 ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
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
 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
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound
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
 the number of values to generate  Returns:
 a stream of
double
values  Throws:

IllegalArgumentException
 ifstreamSize
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:
 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).
 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
 ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
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
 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
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound