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 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(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.
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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.
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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.
|
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Public constructors
SplittableRandom
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
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
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
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
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
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
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
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
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
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
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
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
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
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
boolean nextBoolean ()
Returns a pseudorandom boolean value.
| Returns |
|---|
boolean |
a pseudorandom boolean value
|
nextDouble
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
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
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
int nextInt ()
Returns a pseudorandom int value.
| Returns |
|---|
int |
a pseudorandom int value
|
nextInt
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
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
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
long nextLong ()
Returns a pseudorandom long value.
| Returns |
|---|
long |
a pseudorandom long value
|
nextLong
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
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.
Developers