ThreadLocalRandom - JRE Emulation | JRE Emulation
public class

ThreadLocalRandom

extends Random
java.lang.Object
   ↳ java.util.Random
     ↳ java.util.concurrent.ThreadLocalRandom

Class Overview

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.

Summary

Public Methods
static ThreadLocalRandom current()
Returns the current thread's ThreadLocalRandom.
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.
Protected Methods
int next(int bits)
Returns a pseudo-random uniformly distributed int value of the number of bits specified by the argument bits as described by Donald E.
Inherited Methods
[Expand]
From class java.util.Random
From class java.lang.Object

Public Methods

public static ThreadLocalRandom current ()

Returns the current thread's ThreadLocalRandom.

Returns
  • the current thread's ThreadLocalRandom

public double nextDouble (double n)

Returns a pseudorandom, uniformly distributed double 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

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 returned
bound the upper bound (exclusive)
Returns
  • the next value
Throws
IllegalArgumentException if least greater than or equal to bound

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 returned
bound the upper bound (exclusive)
Returns
  • the next value
Throws
IllegalArgumentException if least greater than or equal to bound

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

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 returned
bound the upper bound (exclusive)
Returns
  • the next value
Throws
IllegalArgumentException if least greater than or equal to bound

public void setSeed (long seed)

Throws UnsupportedOperationException. Setting seeds in this generator is not supported.

Protected Methods

protected int next (int bits)

Returns a pseudo-random uniformly distributed int value of the number of bits specified by the argument bits as described by Donald E. Knuth in The Art of Computer Programming, Volume 2: Seminumerical Algorithms, section 3.2.1.

Most applications will want to use one of this class' convenience methods instead.

Subclasses only need to override this method to alter the behavior of all the public methods.