public class ThreadLocalRandom extends Random
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.
| Modifier and Type | Method and Description |
|---|---|
static ThreadLocalRandom |
current()
Returns the current thread's
ThreadLocalRandom. |
protected int |
next(int bits)
Generates the next pseudorandom number.
|
double |
nextDouble(double n)
Returns a pseudorandom, uniformly distributed
double 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)
Throws
UnsupportedOperationException. |
nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLongpublic static ThreadLocalRandom current()
ThreadLocalRandom.ThreadLocalRandompublic void setSeed(long seed)
UnsupportedOperationException. Setting seeds in
this generator is not supported.setSeed in class Randomseed - the initial seedUnsupportedOperationException - alwaysprotected int next(int bits)
RandomThe general contract of next is that it returns an
int value and if the argument bits is between
1 and 32 (inclusive), then that many low-order
bits of the returned value will be (approximately) independently
chosen bit values, each of which is (approximately) equally
likely to be 0 or 1. The method next is
implemented by class Random by atomically updating the seed to
(seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)(int)(seed >>> (48 - bits)).public int nextInt(int least,
int bound)
least - the least value returnedbound - the upper bound (exclusive)IllegalArgumentException - if least greater than or equal
to boundpublic long nextLong(long n)
n - the bound on the random number to be returned. Must be
positive.IllegalArgumentException - if n is not positivepublic long nextLong(long least,
long bound)
least - the least value returnedbound - the upper bound (exclusive)IllegalArgumentException - if least greater than or equal
to boundpublic double nextDouble(double n)
double value
between 0 (inclusive) and the specified value (exclusive).n - the bound on the random number to be returned. Must be
positive.IllegalArgumentException - if n is not positivepublic double nextDouble(double least,
double bound)
least - the least value returnedbound - the upper bound (exclusive)IllegalArgumentException - if least greater than or equal
to bound Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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