Package jsr166y
Class ThreadLocalRandom
java.lang.Object
java.util.Random
jsr166y.ThreadLocalRandom
- All Implemented Interfaces:
Serializable
,java.util.random.RandomGenerator
A random number generator isolated to the current thread. Like the
global
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
accidently share a ThreadLocalRandom
across multiple threads.
This class also provides additional commonly used bounded random generation methods.
- Since:
- 1.7
- See Also:
-
Nested Class Summary
Nested classes/interfaces inherited from interface java.util.random.RandomGenerator
java.util.random.RandomGenerator.ArbitrarilyJumpableGenerator, java.util.random.RandomGenerator.JumpableGenerator, java.util.random.RandomGenerator.LeapableGenerator, java.util.random.RandomGenerator.SplittableGenerator, java.util.random.RandomGenerator.StreamableGenerator
-
Method Summary
Modifier and TypeMethodDescriptionstatic ThreadLocalRandom
current()
Returns the current thread'sThreadLocalRandom
.protected int
next
(int bits) double
nextDouble
(double n) Returns a pseudorandom, uniformly distributeddouble
value between 0 (inclusive) and the specified value (exclusive).double
nextDouble
(double least, double bound) Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).int
nextInt
(int least, int bound) Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).long
nextLong
(long n) Returns a pseudorandom, uniformly distributed value between 0 (inclusive) and the specified value (exclusive).long
nextLong
(long least, long bound) Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).void
setSeed
(long seed) ThrowsUnsupportedOperationException
.Methods inherited from class java.util.Random
doubles, doubles, doubles, doubles, from, ints, ints, ints, ints, longs, longs, longs, longs, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLong
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface java.util.random.RandomGenerator
isDeprecated, nextExponential, nextFloat, nextFloat, nextGaussian
-
Method Details
-
current
Returns the current thread'sThreadLocalRandom
.- 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
- Throws:
UnsupportedOperationException
- always
-
next
protected int next(int bits) -
nextInt
public int nextInt(int least, int bound) Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).- Parameters:
least
- the least value returnedbound
- the upper bound (exclusive)- Returns:
- the next value
- Throws:
IllegalArgumentException
- if least greater than or equal to bound
-
nextLong
public long nextLong(long n) Returns a pseudorandom, uniformly distributed value between 0 (inclusive) and the specified value (exclusive).- Parameters:
n
- the bound on the random number to be returned. Must be positive.- Returns:
- the next value
- Throws:
IllegalArgumentException
- if n is not positive
-
nextLong
public long nextLong(long least, long bound) Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).- Parameters:
least
- the least value returnedbound
- the upper bound (exclusive)- Returns:
- the next value
- Throws:
IllegalArgumentException
- if least greater than or equal to bound
-
nextDouble
public double nextDouble(double n) Returns a pseudorandom, uniformly distributeddouble
value between 0 (inclusive) and the specified value (exclusive).- Parameters:
n
- the bound on the random number to be returned. Must be positive.- Returns:
- the next value
- Throws:
IllegalArgumentException
- if n is not positive
-
nextDouble
public double nextDouble(double least, double bound) Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).- Parameters:
least
- the least value returnedbound
- the upper bound (exclusive)- Returns:
- the next value
- Throws:
IllegalArgumentException
- if least greater than or equal to bound
-