- java.lang.Object
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- java.util.SplittableRandom
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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. ClassSplittableRandomsupports methods for producing pseudorandom numbers of typeint,long, anddoublewith similar usages as for classRandombut 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 singleSplittableRandomobject. - Instances of SplittableRandom are not thread-safe.
They are designed to be split, not shared, across threads. For
example, a
fork/join-stylecomputation 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
SplittableRandomare not cryptographically secure. Consider instead usingSecureRandomin security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless the system propertyjava.util.secureRandomSeedis set totrue.- Since:
- 1.8
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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.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description DoubleStreamdoubles()Returns an effectively unlimited stream of pseudorandomdoublevalues from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).DoubleStreamdoubles(double randomNumberOrigin, double randomNumberBound)Returns an effectively unlimited stream of pseudorandomdoublevalues from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).DoubleStreamdoubles(long streamSize)Returns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues from this generator and/or one split from it; each value is between zero (inclusive) and one (exclusive).DoubleStreamdoubles(long streamSize, double randomNumberOrigin, double randomNumberBound)Returns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).IntStreamints()Returns an effectively unlimited stream of pseudorandomintvalues from this generator and/or one split from it.IntStreamints(int randomNumberOrigin, int randomNumberBound)Returns an effectively unlimited stream of pseudorandomintvalues from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).IntStreamints(long streamSize)Returns a stream producing the givenstreamSizenumber of pseudorandomintvalues from this generator and/or one split from it.IntStreamints(long streamSize, int randomNumberOrigin, int randomNumberBound)Returns a stream producing the givenstreamSizenumber of pseudorandomintvalues from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).LongStreamlongs()Returns an effectively unlimited stream of pseudorandomlongvalues from this generator and/or one split from it.LongStreamlongs(long streamSize)Returns a stream producing the givenstreamSizenumber of pseudorandomlongvalues from this generator and/or one split from it.LongStreamlongs(long randomNumberOrigin, long randomNumberBound)Returns an effectively unlimited stream of pseudorandomlongvalues from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).LongStreamlongs(long streamSize, long randomNumberOrigin, long randomNumberBound)Returns a stream producing the givenstreamSizenumber of pseudorandomlongvalues from this generator and/or one split from it; each value conforms to the given origin (inclusive) and bound (exclusive).booleannextBoolean()Returns a pseudorandombooleanvalue.voidnextBytes(byte[] bytes)Fills a user-supplied byte array with generated pseudorandom bytes.doublenextDouble()Returns a pseudorandomdoublevalue between zero (inclusive) and one (exclusive).doublenextDouble(double bound)Returns a pseudorandomdoublevalue between 0.0 (inclusive) and the specified bound (exclusive).doublenextDouble(double origin, double bound)Returns a pseudorandomdoublevalue between the specified origin (inclusive) and bound (exclusive).intnextInt()Returns a pseudorandomintvalue.intnextInt(int bound)Returns a pseudorandomintvalue between zero (inclusive) and the specified bound (exclusive).intnextInt(int origin, int bound)Returns a pseudorandomintvalue between the specified origin (inclusive) and the specified bound (exclusive).longnextLong()Returns a pseudorandomlongvalue.longnextLong(long bound)Returns a pseudorandomlongvalue between zero (inclusive) and the specified bound (exclusive).longnextLong(long origin, long bound)Returns a pseudorandomlongvalue between the specified origin (inclusive) and the specified bound (exclusive).SplittableRandomsplit()Constructs and returns a new SplittableRandom instance that shares no mutable state with this instance.
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Constructor Detail
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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
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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.
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Method Detail
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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 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
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nextBytes
public void nextBytes(byte[] bytes)
Fills a user-supplied byte array with generated pseudorandom bytes.- Parameters:
bytes- the byte array to fill with pseudorandom bytes- Throws:
NullPointerException- if bytes is null- Since:
- 10
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nextInt
public int nextInt()
Returns a pseudorandomintvalue.- Returns:
- a pseudorandom
intvalue
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nextInt
public int nextInt(int bound)
Returns a pseudorandomintvalue between zero (inclusive) and the specified bound (exclusive).- Parameters:
bound- the upper bound (exclusive). Must be positive.- Returns:
- a pseudorandom
intvalue between zero (inclusive) and the bound (exclusive) - Throws:
IllegalArgumentException- ifboundis not positive
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nextInt
public int nextInt(int origin, int bound)Returns a pseudorandomintvalue between the specified origin (inclusive) and the specified bound (exclusive).- Parameters:
origin- the least value returnedbound- the upper bound (exclusive)- Returns:
- a pseudorandom
intvalue between the origin (inclusive) and the bound (exclusive) - Throws:
IllegalArgumentException- iforiginis greater than or equal tobound
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nextLong
public long nextLong()
Returns a pseudorandomlongvalue.- Returns:
- a pseudorandom
longvalue
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nextLong
public long nextLong(long bound)
Returns a pseudorandomlongvalue between zero (inclusive) and the specified bound (exclusive).- Parameters:
bound- the upper bound (exclusive). Must be positive.- Returns:
- a pseudorandom
longvalue between zero (inclusive) and the bound (exclusive) - Throws:
IllegalArgumentException- ifboundis not positive
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nextLong
public long nextLong(long origin, long bound)Returns a pseudorandomlongvalue between the specified origin (inclusive) and the specified bound (exclusive).- Parameters:
origin- the least value returnedbound- the upper bound (exclusive)- Returns:
- a pseudorandom
longvalue between the origin (inclusive) and the bound (exclusive) - Throws:
IllegalArgumentException- iforiginis greater than or equal tobound
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nextDouble
public double nextDouble()
Returns a pseudorandomdoublevalue between zero (inclusive) and one (exclusive).- Returns:
- a pseudorandom
doublevalue between zero (inclusive) and one (exclusive)
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nextDouble
public double nextDouble(double bound)
Returns a pseudorandomdoublevalue between 0.0 (inclusive) and the specified bound (exclusive).- Parameters:
bound- the upper bound (exclusive). Must be positive.- Returns:
- a pseudorandom
doublevalue between zero (inclusive) and the bound (exclusive) - Throws:
IllegalArgumentException- ifboundis not positive
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nextDouble
public double nextDouble(double origin, double bound)Returns a pseudorandomdoublevalue between the specified origin (inclusive) and bound (exclusive).- Parameters:
origin- the least value returnedbound- the upper bound (exclusive)- Returns:
- a pseudorandom
doublevalue between the origin (inclusive) and the bound (exclusive) - Throws:
IllegalArgumentException- iforiginis greater than or equal tobound
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nextBoolean
public boolean nextBoolean()
Returns a pseudorandombooleanvalue.- Returns:
- a pseudorandom
booleanvalue
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ints
public IntStream ints(long streamSize)
Returns a stream producing the givenstreamSizenumber of pseudorandomintvalues from this generator and/or one split from it.- Parameters:
streamSize- the number of values to generate- Returns:
- a stream of pseudorandom
intvalues - Throws:
IllegalArgumentException- ifstreamSizeis less than zero
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ints
public IntStream ints()
Returns an effectively unlimited stream of pseudorandomintvalues 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
intvalues
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ints
public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound)
Returns a stream producing the givenstreamSizenumber of pseudorandomintvalues 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
intvalues, each with the given origin (inclusive) and bound (exclusive) - Throws:
IllegalArgumentException- ifstreamSizeis less than zero, orrandomNumberOriginis greater than or equal torandomNumberBound
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ints
public IntStream ints(int randomNumberOrigin, int randomNumberBound)
Returns an effectively unlimited stream of pseudorandomintvalues 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
intvalues, each with the given origin (inclusive) and bound (exclusive) - Throws:
IllegalArgumentException- ifrandomNumberOriginis greater than or equal torandomNumberBound
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longs
public LongStream longs(long streamSize)
Returns a stream producing the givenstreamSizenumber of pseudorandomlongvalues from this generator and/or one split from it.- Parameters:
streamSize- the number of values to generate- Returns:
- a stream of pseudorandom
longvalues - Throws:
IllegalArgumentException- ifstreamSizeis less than zero
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longs
public LongStream longs()
Returns an effectively unlimited stream of pseudorandomlongvalues 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
longvalues
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longs
public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound)
Returns a stream producing the givenstreamSizenumber of pseudorandomlongvalues 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
longvalues, each with the given origin (inclusive) and bound (exclusive) - Throws:
IllegalArgumentException- ifstreamSizeis less than zero, orrandomNumberOriginis greater than or equal torandomNumberBound
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longs
public LongStream longs(long randomNumberOrigin, long randomNumberBound)
Returns an effectively unlimited stream of pseudorandomlongvalues 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
longvalues, each with the given origin (inclusive) and bound (exclusive) - Throws:
IllegalArgumentException- ifrandomNumberOriginis greater than or equal torandomNumberBound
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doubles
public DoubleStream doubles(long streamSize)
Returns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues 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
doublevalues - Throws:
IllegalArgumentException- ifstreamSizeis less than zero
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doubles
public DoubleStream doubles()
Returns an effectively unlimited stream of pseudorandomdoublevalues 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
doublevalues
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doubles
public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)
Returns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues 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
doublevalues, each with the given origin (inclusive) and bound (exclusive) - Throws:
IllegalArgumentException- ifstreamSizeis less than zero, orrandomNumberOriginis greater than or equal torandomNumberBound
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doubles
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
Returns an effectively unlimited stream of pseudorandomdoublevalues 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
doublevalues, each with the given origin (inclusive) and bound (exclusive) - Throws:
IllegalArgumentException- ifrandomNumberOriginis greater than or equal torandomNumberBound
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