Summary: Methods | Protected Methods | Inherited Methods | [Expand All]

Added in API level 21

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.

[Expand]

Inherited Methods

From class java.util.Random

synchronized 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.
boolean	nextBoolean() Returns a pseudo-random uniformly distributed `boolean`.
void	nextBytes(byte[] buf) Fills `buf` with random bytes.
double	nextDouble() Returns a pseudo-random uniformly distributed `double` in the half-open range [0.0, 1.0).
float	nextFloat() Returns a pseudo-random uniformly distributed `float` in the half-open range [0.0, 1.0).
synchronized double	nextGaussian() Returns a pseudo-random (approximately) normally distributed `double` with mean 0.0 and standard deviation 1.0.
int	nextInt(int n) Returns a pseudo-random uniformly distributed `int` in the half-open range [0, n).
int	nextInt() Returns a pseudo-random uniformly distributed `int`.
long	nextLong() Returns a pseudo-random uniformly distributed `long`.
synchronized void	setSeed(long seed) Modifies the seed using a linear congruential formula presented in The Art of Computer Programming, Volume 2, Section 3.2.1.

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals(Object o) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
final void	wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long millis) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

Public Methods

public static ThreadLocalRandom current ()

Added in API level 21

Returns the current thread's ThreadLocalRandom.

Returns

the current thread's ThreadLocalRandom

public double nextDouble (double n)

Added in API level 21

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)

Added in API level 21

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)

Added in API level 21

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)

Added in API level 21

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)

Added in API level 21

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)

Added in API level 21

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

Throws

UnsupportedOperationException	always

Protected Methods

protected int next (int bits)

Added in API level 21

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.

Results

Interfaces

Classes

Enums

Exceptions

ThreadLocalRandom

Class Overview

Summary

Public Methods

public static ThreadLocalRandom current ()

Returns

public double nextDouble (double n)

Parameters

Returns

Throws

public double nextDouble (double least, double bound)

Parameters

Returns

Throws

public int nextInt (int least, int bound)

Parameters

Returns

Throws

public long nextLong (long n)

Parameters

Returns

Throws

public long nextLong (long least, long bound)

Parameters

Returns

Throws

public void setSeed (long seed)

Throws

Protected Methods

protected int next (int bits)