Class ThreadLocalRandom
 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 securitysensitive applications. Additionally,
defaultconstructed instances do not use a cryptographically random
seed unless the system property
java.util.secureRandomSeed
is set to true
.
 Since:
 1.7
 See Also:

Nested Class Summary
Nested classes/interfaces declared in interface java.util.random.RandomGenerator
RandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator

Method Summary
Modifier and TypeMethodDescriptionstatic ThreadLocalRandom
current()
Returns the current thread'sThreadLocalRandom
object.doubles()
Returns an effectively unlimited stream of pseudorandomdouble
values, each between zero (inclusive) and one (exclusive).doubles
(double randomNumberOrigin, double randomNumberBound) Returns an effectively unlimited stream of pseudorandomdouble
values, each conforming to the given origin (inclusive) and bound (exclusive).doubles
(long streamSize) Returns a stream producing the givenstreamSize
number of pseudorandomdouble
values, each between zero (inclusive) and one (exclusive).doubles
(long streamSize, double randomNumberOrigin, double randomNumberBound) Returns a stream producing the givenstreamSize
number of pseudorandomdouble
values, each conforming to the given origin (inclusive) and bound (exclusive).ints()
Returns an effectively unlimited stream of pseudorandomint
values.ints
(int randomNumberOrigin, int randomNumberBound) Returns an effectively unlimited stream of pseudorandomint
values, each conforming to the given origin (inclusive) and bound (exclusive).ints
(long streamSize) Returns a stream producing the givenstreamSize
number of pseudorandomint
values.ints
(long streamSize, int randomNumberOrigin, int randomNumberBound) Returns a stream producing the givenstreamSize
number of pseudorandomint
values, each conforming to the given origin (inclusive) and bound (exclusive).longs()
Returns an effectively unlimited stream of pseudorandomlong
values.longs
(long streamSize) Returns a stream producing the givenstreamSize
number of pseudorandomlong
values.longs
(long randomNumberOrigin, long randomNumberBound) Returns an effectively unlimited stream of pseudorandomlong
values, each conforming to the given origin (inclusive) and bound (exclusive).longs
(long streamSize, long randomNumberOrigin, long randomNumberBound) Returns a stream producing the givenstreamSize
number of pseudorandomlong
, each conforming to the given origin (inclusive) and bound (exclusive).protected int
next
(int bits) Generates a pseudorandom number with the indicated number of loworder bits.double
nextDouble
(double bound) Returns a pseudorandomly chosendouble
value between zero (inclusive) and the specified bound (exclusive).double
nextDouble
(double origin, double bound) Returns a pseudorandomly chosendouble
value between the specified origin (inclusive) and the specified bound (exclusive).float
nextFloat
(float bound) Returns a pseudorandomly chosenfloat
value between zero (inclusive) and the specified bound (exclusive).float
nextFloat
(float origin, float bound) Returns a pseudorandomly chosenfloat
value between the specified origin (inclusive) and the specified bound (exclusive).int
nextInt
(int bound) Returns a pseudorandom, uniformly distributedint
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.int
nextInt
(int origin, int bound) Returns a pseudorandomly chosenint
value between the specified origin (inclusive) and the specified bound (exclusive).long
nextLong
(long bound) Returns a pseudorandomly chosenlong
value between zero (inclusive) and the specified bound (exclusive).long
nextLong
(long origin, long bound) Returns a pseudorandomly chosenlong
value between the specified origin (inclusive) and the specified bound (exclusive).void
setSeed
(long seed) ThrowsUnsupportedOperationException
.Methods declared in class java.util.Random
from, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextLong
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods declared in interface java.util.random.RandomGenerator
equiDoubles, isDeprecated, nextExponential, nextGaussian

Method Details

current
Returns the current thread'sThreadLocalRandom
object. Methods of this object should be called only by the current thread, not by other threads. Returns:
 the current thread's
ThreadLocalRandom

setSeed
public void setSeed(long seed) ThrowsUnsupportedOperationException
. Setting seeds in this generator is not supported. Overrides:
setSeed
in classRandom
 Parameters:
seed
 the seed value Throws:
UnsupportedOperationException
 always

next
protected int next(int bits) Generates a pseudorandom number with the indicated number of loworder bits. Because this class has no subclasses, this method cannot be invoked or overridden. 
nextInt
public int nextInt(int bound) Returns a pseudorandom, uniformly distributedint
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The general contract ofnextInt
is that oneint
value in the specified range is pseudorandomly generated and returned. Allbound
possibleint
values are produced with (approximately) equal probability. Specified by:
nextInt
in interfaceRandomGenerator
 Overrides:
nextInt
in classRandom
 Parameters:
bound
 the upper bound (exclusive). Must be positive. Returns:
 the next pseudorandom, uniformly distributed
int
value between zero (inclusive) andbound
(exclusive) from this random number generator's sequence  Throws:
IllegalArgumentException
 if bound is not positive

nextInt
public int nextInt(int origin, int bound) Returns a pseudorandomly chosenint
value between the specified origin (inclusive) and the specified bound (exclusive). Parameters:
origin
 the least value that can be returnedbound
 the upper bound (exclusive) for the returned value Returns:
 a pseudorandomly chosen
int
value between the origin (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 iforigin
is greater than or equal tobound

nextLong
public long nextLong(long bound) Returns a pseudorandomly chosenlong
value 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
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 pseudorandomly chosenlong
value between the specified origin (inclusive) and the specified bound (exclusive). Parameters:
origin
 the least value that can be returnedbound
 the upper bound (exclusive) for the returned value Returns:
 a pseudorandomly chosen
long
value between the origin (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 iforigin
is greater than or equal tobound

nextFloat
public float nextFloat(float bound) Returns a pseudorandomly chosenfloat
value 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
float
value between zero (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 ifbound
is not both positive and finite

nextFloat
public float nextFloat(float origin, float bound) Returns a pseudorandomly chosenfloat
value between the specified origin (inclusive) and the specified bound (exclusive). Implementation Note:
 Parameters:
origin
 the least value that can be returnedbound
 the upper bound (exclusive) Returns:
 a pseudorandomly chosen
float
value between the origin (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 iforigin
is not finite, orbound
is not finite, ororigin
is greater than or equal tobound

nextDouble
public double nextDouble(double bound) Returns a pseudorandomly chosendouble
value 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
double
value between zero (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 ifbound
is not both positive and finite

nextDouble
public double nextDouble(double origin, double bound) Returns a pseudorandomly chosendouble
value between the specified origin (inclusive) and the specified bound (exclusive). Implementation Note:
 Parameters:
origin
 the least value that can be returnedbound
 the upper bound (exclusive) for the returned value Returns:
 a pseudorandomly chosen
double
value between the origin (inclusive) and the bound (exclusive)  Throws:
IllegalArgumentException
 iforigin
is not finite, orbound
is not finite, ororigin
is greater than or equal tobound

ints
Returns a stream producing the givenstreamSize
number of pseudorandomint
values.A pseudorandom
int
value is generated as if it's the result of calling the methodRandom.nextInt()
. Specified by:
ints
in interfaceRandomGenerator
 Overrides:
ints
in classRandom
 Parameters:
streamSize
 the number of values to generate Returns:
 a stream of pseudorandom
int
values  Throws:
IllegalArgumentException
 ifstreamSize
is less than zero Since:
 1.8

ints
Returns an effectively unlimited stream of pseudorandomint
values.A pseudorandom
int
value is generated as if it's the result of calling the methodRandom.nextInt()
. Specified by:
ints
in interfaceRandomGenerator
 Overrides:
ints
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
ints(Long.MAX_VALUE)
.  Returns:
 a stream of pseudorandom
int
values  Since:
 1.8

ints
Returns a stream producing the givenstreamSize
number of pseudorandomint
values, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom
int
value 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:
ints
in interfaceRandomGenerator
 Overrides:
ints
in classRandom
 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
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
 Since:
 1.8

ints
Returns an effectively unlimited stream of pseudorandomint
values, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom
int
value 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:
ints
in interfaceRandomGenerator
 Overrides:
ints
in classRandom
 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
int
values, each with the given origin (inclusive) and bound (exclusive)  Throws:
IllegalArgumentException
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8

longs
Returns a stream producing the givenstreamSize
number of pseudorandomlong
values.A pseudorandom
long
value is generated as if it's the result of calling the methodRandom.nextLong()
. Specified by:
longs
in interfaceRandomGenerator
 Overrides:
longs
in classRandom
 Parameters:
streamSize
 the number of values to generate Returns:
 a stream of pseudorandom
long
values  Throws:
IllegalArgumentException
 ifstreamSize
is less than zero Since:
 1.8

longs
Returns an effectively unlimited stream of pseudorandomlong
values.A pseudorandom
long
value is generated as if it's the result of calling the methodRandom.nextLong()
. Specified by:
longs
in interfaceRandomGenerator
 Overrides:
longs
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
longs(Long.MAX_VALUE)
.  Returns:
 a stream of pseudorandom
long
values  Since:
 1.8

longs
Returns a stream producing the givenstreamSize
number of pseudorandomlong
, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom
long
value 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 overrepresented 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:
longs
in interfaceRandomGenerator
 Overrides:
longs
in classRandom
 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
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
 Since:
 1.8

longs
Returns an effectively unlimited stream of pseudorandomlong
values, each conforming to the given origin (inclusive) and bound (exclusive).A pseudorandom
long
value 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 overrepresented 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:
longs
in interfaceRandomGenerator
 Overrides:
longs
in classRandom
 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
long
values, each with the given origin (inclusive) and bound (exclusive)  Throws:
IllegalArgumentException
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8

doubles
Returns a stream producing the givenstreamSize
number of pseudorandomdouble
values, each between zero (inclusive) and one (exclusive).A pseudorandom
double
value is generated as if it's the result of calling the methodRandom.nextDouble()
. Specified by:
doubles
in interfaceRandomGenerator
 Overrides:
doubles
in classRandom
 Parameters:
streamSize
 the number of values to generate Returns:
 a stream of
double
values  Throws:
IllegalArgumentException
 ifstreamSize
is less than zero Since:
 1.8

doubles
Returns an effectively unlimited stream of pseudorandomdouble
values, each between zero (inclusive) and one (exclusive).A pseudorandom
double
value is generated as if it's the result of calling the methodRandom.nextDouble()
. Specified by:
doubles
in interfaceRandomGenerator
 Overrides:
doubles
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
doubles(Long.MAX_VALUE)
.  Returns:
 a stream of pseudorandom
double
values  Since:
 1.8

doubles
Returns a stream producing the givenstreamSize
number of pseudorandomdouble
values, each conforming to the given origin (inclusive) and bound (exclusive). Specified by:
doubles
in interfaceRandomGenerator
 Overrides:
doubles
in classRandom
 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
double
values, each with the given origin (inclusive) and bound (exclusive)  Throws:
IllegalArgumentException
 ifstreamSize
is less than zero, orrandomNumberOrigin
is not finite, orrandomNumberBound
is not finite, orrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8

doubles
Returns an effectively unlimited stream of pseudorandomdouble
values, each conforming to the given origin (inclusive) and bound (exclusive). Specified by:
doubles
in interfaceRandomGenerator
 Overrides:
doubles
in classRandom
 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
double
values, each with the given origin (inclusive) and bound (exclusive)  Throws:
IllegalArgumentException
 ifrandomNumberOrigin
is not finite, orrandomNumberBound
is not finite, orrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8
