- All Implemented Interfaces:
- Serializable,- RandomGenerator
Random
 generator used by the Math class,
 a ThreadLocalRandom is initialized
 with an internally generated seed that may not otherwise be
 modified. When applicable, use of ThreadLocalRandom rather
 than shared Random objects in concurrent programs will
 typically encounter much less overhead and contention.  Use of
 ThreadLocalRandom is particularly appropriate when multiple
 tasks (for example, each a ForkJoinTask) use random numbers
 in parallel in thread pools.
 Usages of this class should typically be of the form:
 ThreadLocalRandom.current().nextX(...) (where
 X is Int, Long, etc).
 When all usages are of this form, it is never possible to
 accidentally share a ThreadLocalRandom across multiple threads.
 
This class also provides additional commonly used bounded random generation methods.
Instances of ThreadLocalRandom 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.
- Since:
- 1.7
- See Also:
- 
Nested Class SummaryNested classes/interfaces declared in interface java.util.random.RandomGeneratorRandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator
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Method SummaryModifier and TypeMethodDescriptionstatic ThreadLocalRandomcurrent()Returns the current thread'sThreadLocalRandomobject.doubles()Returns an effectively unlimited stream of pseudorandomdoublevalues, each between zero (inclusive) and one (exclusive).doubles(double randomNumberOrigin, double randomNumberBound) Returns an effectively unlimited stream of pseudorandomdoublevalues, each conforming to the given origin (inclusive) and bound (exclusive).doubles(long streamSize) Returns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues, each between zero (inclusive) and one (exclusive).doubles(long streamSize, double randomNumberOrigin, double randomNumberBound) Returns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues, each conforming to the given origin (inclusive) and bound (exclusive).ints()Returns an effectively unlimited stream of pseudorandomintvalues.ints(int randomNumberOrigin, int randomNumberBound) Returns an effectively unlimited stream of pseudorandomintvalues, each conforming to the given origin (inclusive) and bound (exclusive).ints(long streamSize) Returns a stream producing the givenstreamSizenumber of pseudorandomintvalues.ints(long streamSize, int randomNumberOrigin, int randomNumberBound) Returns a stream producing the givenstreamSizenumber of pseudorandomintvalues, each conforming to the given origin (inclusive) and bound (exclusive).longs()Returns an effectively unlimited stream of pseudorandomlongvalues.longs(long streamSize) Returns a stream producing the givenstreamSizenumber of pseudorandomlongvalues.longs(long randomNumberOrigin, long randomNumberBound) Returns an effectively unlimited stream of pseudorandomlongvalues, each conforming to the given origin (inclusive) and bound (exclusive).longs(long streamSize, long randomNumberOrigin, long randomNumberBound) Returns a stream producing the givenstreamSizenumber of pseudorandomlong, each conforming to the given origin (inclusive) and bound (exclusive).protected intnext(int bits) Generates a pseudorandom number with the indicated number of low-order bits.doublenextDouble(double bound) Returns a pseudorandomly chosendoublevalue between zero (inclusive) and the specified bound (exclusive).doublenextDouble(double origin, double bound) Returns a pseudorandomly chosendoublevalue between the specified origin (inclusive) and the specified bound (exclusive).floatnextFloat(float bound) Returns a pseudorandomly chosenfloatvalue between zero (inclusive) and the specified bound (exclusive).floatnextFloat(float origin, float bound) Returns a pseudorandomly chosenfloatvalue between the specified origin (inclusive) and the specified bound (exclusive).intnextInt(int bound) Returns a pseudorandom, uniformly distributedintvalue between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.intnextInt(int origin, int bound) Returns a pseudorandomly chosenintvalue between the specified origin (inclusive) and the specified bound (exclusive).longnextLong(long bound) Returns a pseudorandomly chosenlongvalue between zero (inclusive) and the specified bound (exclusive).longnextLong(long origin, long bound) Returns a pseudorandomly chosenlongvalue between the specified origin (inclusive) and the specified bound (exclusive).voidsetSeed(long seed) ThrowsUnsupportedOperationException.Methods declared in class java.util.Randomfrom, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextLongMethods declared in class java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitMethods declared in interface java.util.random.RandomGeneratorisDeprecated, nextExponential, nextGaussian
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Method Details- 
currentReturns the current thread'sThreadLocalRandomobject. Methods of this object should be called only by the current thread, not by other threads.- Returns:
- the current thread's ThreadLocalRandom
 
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setSeedpublic void setSeed(long seed) ThrowsUnsupportedOperationException. Setting seeds in this generator is not supported.- Overrides:
- setSeedin class- Random
- Parameters:
- seed- the seed value
- Throws:
- UnsupportedOperationException- always
 
- 
nextprotected int next(int bits) Generates a pseudorandom number with the indicated number of low-order bits. Because this class has no subclasses, this method cannot be invoked or overridden.
- 
nextIntpublic int nextInt(int bound) Returns a pseudorandom, uniformly distributedintvalue between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The general contract ofnextIntis that oneintvalue in the specified range is pseudorandomly generated and returned. Allboundpossibleintvalues are produced with (approximately) equal probability.- Specified by:
- nextIntin interface- RandomGenerator
- Overrides:
- nextIntin class- Random
- Parameters:
- bound- the upper bound (exclusive). Must be positive.
- Returns:
- the next pseudorandom, uniformly distributed intvalue between zero (inclusive) andbound(exclusive) from this random number generator's sequence
- Throws:
- IllegalArgumentException- if bound is not positive
 
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nextIntpublic int nextInt(int origin, int bound) Returns a pseudorandomly chosenintvalue between the specified origin (inclusive) and the specified bound (exclusive).- Parameters:
- origin- the least value that can be returned
- bound- the upper bound (exclusive) for the returned value
- Returns:
- a pseudorandomly chosen intvalue between the origin (inclusive) and the bound (exclusive)
- Throws:
- IllegalArgumentException- if- originis greater than or equal to- bound
 
- 
nextLongpublic long nextLong(long bound) Returns a pseudorandomly chosenlongvalue between zero (inclusive) and the specified bound (exclusive).- Parameters:
- bound- the upper bound (exclusive) for the returned value. Must be positive.
- Returns:
- a pseudorandomly chosen longvalue between zero (inclusive) and the bound (exclusive)
- Throws:
- IllegalArgumentException- if- boundis not positive
 
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nextLongpublic long nextLong(long origin, long bound) Returns a pseudorandomly chosenlongvalue between the specified origin (inclusive) and the specified bound (exclusive).- Parameters:
- origin- the least value that can be returned
- bound- the upper bound (exclusive) for the returned value
- Returns:
- a pseudorandomly chosen longvalue between the origin (inclusive) and the bound (exclusive)
- Throws:
- IllegalArgumentException- if- originis greater than or equal to- bound
 
- 
nextFloatpublic float nextFloat(float bound) Returns a pseudorandomly chosenfloatvalue between zero (inclusive) and the specified bound (exclusive).- Implementation Note:
- Parameters:
- bound- the upper bound (exclusive) for the returned value. Must be positive and finite
- Returns:
- a pseudorandomly chosen floatvalue between zero (inclusive) and the bound (exclusive)
- Throws:
- IllegalArgumentException- if- boundis not both positive and finite
 
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nextFloatpublic float nextFloat(float origin, float bound) Returns a pseudorandomly chosenfloatvalue between the specified origin (inclusive) and the specified bound (exclusive).- Implementation Note:
- Parameters:
- origin- the least value that can be returned
- bound- the upper bound (exclusive)
- Returns:
- a pseudorandomly chosen floatvalue between the origin (inclusive) and the bound (exclusive)
- Throws:
- IllegalArgumentException- if- originis not finite, or- boundis not finite, or- originis greater than or equal to- bound
 
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nextDoublepublic double nextDouble(double bound) Returns a pseudorandomly chosendoublevalue between zero (inclusive) and the specified bound (exclusive).- Implementation Note:
- Parameters:
- bound- the upper bound (exclusive) for the returned value. Must be positive and finite
- Returns:
- a pseudorandomly chosen doublevalue between zero (inclusive) and the bound (exclusive)
- Throws:
- IllegalArgumentException- if- boundis not both positive and finite
 
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nextDoublepublic double nextDouble(double origin, double bound) Returns a pseudorandomly chosendoublevalue between the specified origin (inclusive) and the specified bound (exclusive).- Implementation Note:
- Parameters:
- origin- the least value that can be returned
- bound- the upper bound (exclusive) for the returned value
- Returns:
- a pseudorandomly chosen doublevalue between the origin (inclusive) and the bound (exclusive)
- Throws:
- IllegalArgumentException- if- originis not finite, or- boundis not finite, or- originis greater than or equal to- bound
 
- 
intsReturns a stream producing the givenstreamSizenumber of pseudorandomintvalues.A pseudorandom intvalue is generated as if it's the result of calling the methodRandom.nextInt().- Specified by:
- intsin interface- RandomGenerator
- Overrides:
- intsin class- Random
- Parameters:
- streamSize- the number of values to generate
- Returns:
- a stream of pseudorandom intvalues
- Throws:
- IllegalArgumentException- if- streamSizeis less than zero
- Since:
- 1.8
 
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intsReturns an effectively unlimited stream of pseudorandomintvalues.A pseudorandom intvalue is generated as if it's the result of calling the methodRandom.nextInt().- Specified by:
- intsin interface- RandomGenerator
- Overrides:
- intsin class- Random
- Implementation Note:
- This method is implemented to be equivalent to
           ints(Long.MAX_VALUE).
- Returns:
- a stream of pseudorandom intvalues
- Since:
- 1.8
 
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intsReturns a stream producing the givenstreamSizenumber of pseudorandomintvalues, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom intvalue is generated as if it's the result of calling the following method with the origin and bound:int nextInt(int origin, int bound) { int n = bound - origin; if (n > 0) { return nextInt(n) + origin; } else { // range not representable as int int r; do { r = nextInt(); } while (r < origin || r >= bound); return r; } }- Specified by:
- intsin interface- RandomGenerator
- Overrides:
- intsin class- Random
- 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 intvalues, each with the given origin (inclusive) and bound (exclusive)
- Throws:
- IllegalArgumentException- if- streamSizeis less than zero, or- randomNumberOriginis greater than or equal to- randomNumberBound
- Since:
- 1.8
 
- 
intsReturns an effectively unlimited stream of pseudorandomintvalues, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom intvalue is generated as if it's the result of calling the following method with the origin and bound:int nextInt(int origin, int bound) { int n = bound - origin; if (n > 0) { return nextInt(n) + origin; } else { // range not representable as int int r; do { r = nextInt(); } while (r < origin || r >= bound); return r; } }- Specified by:
- intsin interface- RandomGenerator
- Overrides:
- intsin class- Random
- 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 intvalues, each with the given origin (inclusive) and bound (exclusive)
- Throws:
- IllegalArgumentException- if- randomNumberOriginis greater than or equal to- randomNumberBound
- Since:
- 1.8
 
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longsReturns a stream producing the givenstreamSizenumber of pseudorandomlongvalues.A pseudorandom longvalue is generated as if it's the result of calling the methodRandom.nextLong().- Specified by:
- longsin interface- RandomGenerator
- Overrides:
- longsin class- Random
- Parameters:
- streamSize- the number of values to generate
- Returns:
- a stream of pseudorandom longvalues
- Throws:
- IllegalArgumentException- if- streamSizeis less than zero
- Since:
- 1.8
 
- 
longsReturns an effectively unlimited stream of pseudorandomlongvalues.A pseudorandom longvalue is generated as if it's the result of calling the methodRandom.nextLong().- Specified by:
- longsin interface- RandomGenerator
- Overrides:
- longsin class- Random
- Implementation Note:
- This method is implemented to be equivalent to
           longs(Long.MAX_VALUE).
- Returns:
- a stream of pseudorandom longvalues
- Since:
- 1.8
 
- 
longsReturns a stream producing the givenstreamSizenumber of pseudorandomlong, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom longvalue is generated as if it's the result of calling the following method with the origin and bound:long nextLong(long origin, long bound) { long r = nextLong(); long n = bound - origin, m = n - 1; if ((n & m) == 0L) // power of two r = (r & m) + origin; else if (n > 0L) { // reject over-represented candidates for (long u = r >>> 1; // ensure nonnegative u + m - (r = u % n) < 0L; // rejection check u = nextLong() >>> 1) // retry ; r += origin; } else { // range not representable as long while (r < origin || r >= bound) r = nextLong(); } return r; }- Specified by:
- longsin interface- RandomGenerator
- Overrides:
- longsin class- Random
- 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 longvalues, each with the given origin (inclusive) and bound (exclusive)
- Throws:
- IllegalArgumentException- if- streamSizeis less than zero, or- randomNumberOriginis greater than or equal to- randomNumberBound
- Since:
- 1.8
 
- 
longsReturns an effectively unlimited stream of pseudorandomlongvalues, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom longvalue is generated as if it's the result of calling the following method with the origin and bound:long nextLong(long origin, long bound) { long r = nextLong(); long n = bound - origin, m = n - 1; if ((n & m) == 0L) // power of two r = (r & m) + origin; else if (n > 0L) { // reject over-represented candidates for (long u = r >>> 1; // ensure nonnegative u + m - (r = u % n) < 0L; // rejection check u = nextLong() >>> 1) // retry ; r += origin; } else { // range not representable as long while (r < origin || r >= bound) r = nextLong(); } return r; }- Specified by:
- longsin interface- RandomGenerator
- Overrides:
- longsin class- Random
- 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 longvalues, each with the given origin (inclusive) and bound (exclusive)
- Throws:
- IllegalArgumentException- if- randomNumberOriginis greater than or equal to- randomNumberBound
- Since:
- 1.8
 
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doublesReturns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues, each between zero (inclusive) and one (exclusive).A pseudorandom doublevalue is generated as if it's the result of calling the methodRandom.nextDouble().- Specified by:
- doublesin interface- RandomGenerator
- Overrides:
- doublesin class- Random
- Parameters:
- streamSize- the number of values to generate
- Returns:
- a stream of doublevalues
- Throws:
- IllegalArgumentException- if- streamSizeis less than zero
- Since:
- 1.8
 
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doublesReturns an effectively unlimited stream of pseudorandomdoublevalues, each between zero (inclusive) and one (exclusive).A pseudorandom doublevalue is generated as if it's the result of calling the methodRandom.nextDouble().- Specified by:
- doublesin interface- RandomGenerator
- Overrides:
- doublesin class- Random
- Implementation Note:
- This method is implemented to be equivalent to
           doubles(Long.MAX_VALUE).
- Returns:
- a stream of pseudorandom doublevalues
- Since:
- 1.8
 
- 
doublesReturns a stream producing the givenstreamSizenumber of pseudorandomdoublevalues, each conforming to the given origin (inclusive) and bound (exclusive).- Specified by:
- doublesin interface- RandomGenerator
- Overrides:
- doublesin class- Random
- 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 doublevalues, each with the given origin (inclusive) and bound (exclusive)
- Throws:
- IllegalArgumentException- if- streamSizeis less than zero, or- randomNumberOriginis not finite, or- randomNumberBoundis not finite, or- randomNumberOriginis greater than or equal to- randomNumberBound
- Since:
- 1.8
 
- 
doublesReturns an effectively unlimited stream of pseudorandomdoublevalues, each conforming to the given origin (inclusive) and bound (exclusive).- Specified by:
- doublesin interface- RandomGenerator
- Overrides:
- doublesin class- Random
- 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 doublevalues, each with the given origin (inclusive) and bound (exclusive)
- Throws:
- IllegalArgumentException- if- randomNumberOriginis not finite, or- randomNumberBoundis not finite, or- randomNumberOriginis greater than or equal to- randomNumberBound
- Since:
- 1.8
 
 
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