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 single SplittableRandom
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 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 securitysensitive applications. Additionally,
defaultconstructed 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).

boolean

nextBoolean()
Returns a pseudorandom boolean value.

double

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

double

nextDouble(double bound)
Returns a pseudorandom double value between 0.0
(inclusive) and the specified bound (exclusive).

double

nextDouble(double origin, double bound)
Returns a pseudorandom double value between the specified
origin (inclusive) and bound (exclusive).

int

nextInt()
Returns a pseudorandom int value.

int

nextInt(int origin, int bound)
Returns a pseudorandom int value between the specified
origin (inclusive) and the specified bound (exclusive).

int

nextInt(int bound)
Returns a pseudorandom int value between zero (inclusive)
and the specified bound (exclusive).

long

nextLong(long bound)
Returns a pseudorandom long value between zero (inclusive)
and the specified bound (exclusive).

long

nextLong()
Returns a pseudorandom long value.

long

nextLong(long origin, long bound)
Returns a pseudorandom long 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.

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 millis, int nanos)
Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object, or
some other thread interrupts the current thread, or a certain
amount of real time has elapsed.

final
void

wait(long millis)
Causes the current thread to wait until either another thread invokes the
notify() method or the
notifyAll() method for this object, or a
specified amount of time has elapsed.

final
void

wait()
Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object.


Public constructors
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

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.
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 
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)
.
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) 
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) 
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 
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 (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) 
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 
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) 
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

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

nextDouble
public double nextDouble ()
Returns a pseudorandom double
value between zero
(inclusive) and one (exclusive).
Returns 
double 
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 
double : the upper bound (exclusive). Must be positive. 
Returns 
double 
a pseudorandom double value between zero
(inclusive) and the bound (exclusive) 
nextDouble
public double nextDouble (double origin,
double bound)
Returns a pseudorandom double
value between the specified
origin (inclusive) and bound (exclusive).
Parameters 
origin 
double : the least value returned 
bound 
double : the upper bound (exclusive) 
Returns 
double 
a pseudorandom double value between the origin
(inclusive) and the bound (exclusive) 
nextInt
public int nextInt ()
Returns a pseudorandom int
value.
Returns 
int 
a pseudorandom int value

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 
int : the least value returned 
bound 
int : the upper bound (exclusive) 
Returns 
int 
a pseudorandom int value between the origin
(inclusive) and the bound (exclusive) 
nextInt
public int nextInt (int bound)
Returns a pseudorandom int
value between zero (inclusive)
and the specified bound (exclusive).
Parameters 
bound 
int : the upper bound (exclusive). Must be positive. 
Returns 
int 
a pseudorandom int value between zero
(inclusive) and the bound (exclusive) 
nextLong
public long nextLong (long bound)
Returns a pseudorandom long
value between zero (inclusive)
and the specified bound (exclusive).
Parameters 
bound 
long : the upper bound (exclusive). Must be positive. 
Returns 
long 
a pseudorandom long value between zero
(inclusive) and the bound (exclusive) 
nextLong
public long nextLong ()
Returns a pseudorandom long
value.
Returns 
long 
a pseudorandom long value

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 
long : the least value returned 
bound 
long : the upper bound (exclusive) 
Returns 
long 
a pseudorandom long value between the origin
(inclusive) and the bound (exclusive) 
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.