Added in API level 21

ThreadLocalRandom

class ThreadLocalRandom : Random

kotlin.Any
↳	java.util.Random
	↳	java.util.concurrent.ThreadLocalRandom

A random number generator (with period 264) isolated to the current thread. Like the global java.util.Random generator used by the java.lang.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 java.security.SecureRandom in security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless the java.lang.System#getProperty java.util.secureRandomSeed is set to true.

Summary

Public methods
static ThreadLocalRandom!	current() Returns the current thread's ThreadLocalRandom object.
DoubleStream!	doubles() Returns an effectively unlimited stream of pseudorandom double values, each between zero (inclusive) and one (exclusive).
DoubleStream!	doubles(randomNumberOrigin: Double, randomNumberBound: Double) Returns an effectively unlimited stream of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).
DoubleStream!	doubles(streamSize: Long) Returns a stream producing the given streamSize number of pseudorandom double values, each between zero (inclusive) and one (exclusive).
DoubleStream!	doubles(streamSize: Long, randomNumberOrigin: Double, randomNumberBound: Double) Returns a stream producing the given streamSize number of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).
IntStream!	ints() Returns an effectively unlimited stream of pseudorandom int values.
IntStream!	ints(randomNumberOrigin: Int, randomNumberBound: Int) Returns an effectively unlimited stream of pseudorandom int values, each conforming to the given origin (inclusive) and bound (exclusive).
IntStream!	ints(streamSize: Long) Returns a stream producing the given streamSize number of pseudorandom int values.
IntStream!	ints(streamSize: Long, randomNumberOrigin: Int, randomNumberBound: Int) Returns a stream producing the given streamSize number of pseudorandom int values, each conforming to the given origin (inclusive) and bound (exclusive).
LongStream!	longs() Returns an effectively unlimited stream of pseudorandom long values.
LongStream!	longs(streamSize: Long) Returns a stream producing the given streamSize number of pseudorandom long values.
LongStream!	longs(randomNumberOrigin: Long, randomNumberBound: Long) Returns an effectively unlimited stream of pseudorandom long values, each conforming to the given origin (inclusive) and bound (exclusive).
LongStream!	longs(streamSize: Long, randomNumberOrigin: Long, randomNumberBound: Long) Returns a stream producing the given streamSize number of pseudorandom long, each conforming to the given origin (inclusive) and bound (exclusive).
Boolean	nextBoolean() Returns the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence.
Double	nextDouble() Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.
Double	nextDouble(bound: Double) Returns a pseudorandomly chosen double value between zero (inclusive) and the specified bound (exclusive).
Double	nextDouble(origin: Double, bound: Double) Returns a pseudorandomly chosen double value between the specified origin (inclusive) and the specified bound (exclusive).
Float	nextFloat() Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.
Float	nextFloat(bound: Float) Returns a pseudorandomly chosen float value between zero (inclusive) and the specified bound (exclusive).
Float	nextFloat(origin: Float, bound: Float) Returns a pseudorandomly chosen float value between the specified origin (inclusive) and the specified bound (exclusive).
Int	nextInt() Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence.
Int	nextInt(bound: Int) Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
Int	nextInt(origin: Int, bound: Int) Returns a pseudorandomly chosen int value between the specified origin (inclusive) and the specified bound (exclusive).
Long	nextLong() Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence.
Long	nextLong(bound: Long) Returns a pseudorandomly chosen long value between zero (inclusive) and the specified bound (exclusive).
Long	nextLong(origin: Long, bound: Long) Returns a pseudorandomly chosen long value between the specified origin (inclusive) and the specified bound (exclusive).
Unit	setSeed(seed: Long) Throws UnsupportedOperationException.

Protected methods
Int	next(bits: Int) Generates a pseudorandom number with the indicated number of low-order bits.

Inherited functions
From class RandomGenerator Boolean isDeprecated() Return true if the implementation of RandomGenerator (algorithm) has been marked for deprecation. Double nextDouble(bound: Double) Returns a pseudorandomly chosen double value between zero (inclusive) and the specified bound (exclusive). Double nextDouble(origin: Double, bound: Double) Returns a pseudorandomly chosen double value between the specified origin (inclusive) and the specified bound (exclusive). Double nextExponential() Returns a nonnegative double value pseudorandomly chosen from an exponential distribution whose mean is 1. Float nextFloat(bound: Float) Returns a pseudorandomly chosen float value between zero (inclusive) and the specified bound (exclusive). Float nextFloat(origin: Float, bound: Float) Returns a pseudorandomly chosen float value between the specified origin (inclusive) and the specified bound (exclusive). Double nextGaussian(mean: Double, stddev: Double) Returns a double value pseudorandomly chosen from a Gaussian (normal) distribution with a mean and standard deviation specified by the arguments. Int nextInt(origin: Int, bound: Int) Returns a pseudorandomly chosen int value between the specified origin (inclusive) and the specified bound (exclusive). Long nextLong(bound: Long) Returns a pseudorandomly chosen long value between zero (inclusive) and the specified bound (exclusive). Long nextLong(origin: Long, bound: Long) Returns a pseudorandomly chosen long value between the specified origin (inclusive) and the specified bound (exclusive).
From class Random Unit nextBytes(bytes: ByteArray!) Generates random bytes and places them into a user-supplied byte array. The number of random bytes produced is equal to the length of the byte array. Double nextGaussian() Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence. The general contract of nextGaussian is that one double value, chosen from (approximately) the usual normal distribution with mean 0.0 and standard deviation 1.0, is pseudorandomly generated and returned.

Public methods

current

Added in API level 21

static fun current(): ThreadLocalRandom!

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

Return
ThreadLocalRandom!	the current thread's ThreadLocalRandom

doubles

Added in API level 24

fun doubles(): DoubleStream!

Returns an effectively unlimited stream of pseudorandom double values, each between zero (inclusive) and one (exclusive).

A pseudorandom double value is generated as if it's the result of calling the method nextDouble().

Return
DoubleStream!	a stream of pseudorandom double values

doubles

Added in API level 24

fun doubles(
    randomNumberOrigin: Double, 
    randomNumberBound: Double
): DoubleStream!

Returns an effectively unlimited stream of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom double value is generated as if it's the result of calling the following method with the origin and bound:

<code>double nextDouble(double origin, double bound) {
    double r = nextDouble();
    r = r * (bound - origin) + origin;
    if (r &gt;= bound) // correct for rounding
      r = Math.nextDown(bound);
    return r;
  }</code>

Parameters
randomNumberOrigin	Double: the origin (inclusive) of each random value
randomNumberBound	Double: the bound (exclusive) of each random value

Return
DoubleStream!	a stream of pseudorandom double values, each with the given origin (inclusive) and bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if randomNumberOrigin is greater than or equal to randomNumberBound

doubles

Added in API level 24

fun doubles(streamSize: Long): DoubleStream!

Returns a stream producing the given streamSize number of pseudorandom double values, each between zero (inclusive) and one (exclusive).

A pseudorandom double value is generated as if it's the result of calling the method nextDouble().

Parameters
streamSize	Long: the number of values to generate

Return
DoubleStream!	a stream of double values

Exceptions
java.lang.IllegalArgumentException	if streamSize is less than zero

doubles

Added in API level 24

fun doubles(
    streamSize: Long, 
    randomNumberOrigin: Double, 
    randomNumberBound: Double
): DoubleStream!

Returns a stream producing the given streamSize number of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom double value is generated as if it's the result of calling the following method with the origin and bound:

<code>double nextDouble(double origin, double bound) {
    double r = nextDouble();
    r = r * (bound - origin) + origin;
    if (r &gt;= bound) // correct for rounding
      r = Math.nextDown(bound);
    return r;
  }</code>

Parameters
streamSize	Long: the number of values to generate
randomNumberOrigin	Double: the origin (inclusive) of each random value
randomNumberBound	Double: the bound (exclusive) of each random value

Return
DoubleStream!	a stream of pseudorandom double values, each with the given origin (inclusive) and bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if streamSize is less than zero, or randomNumberOrigin is not finite, or randomNumberBound is not finite, or randomNumberOrigin is greater than or equal to randomNumberBound

ints

Added in API level 24

fun ints(): IntStream!

Returns an effectively unlimited stream of pseudorandom int values.

A pseudorandom int value is generated as if it's the result of calling the method nextInt().

Return
IntStream!	a stream of pseudorandom int values

ints

Added in API level 24

fun ints(
    randomNumberOrigin: Int, 
    randomNumberBound: Int
): IntStream!

Returns an effectively unlimited stream of pseudorandom int 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:

<code>int nextInt(int origin, int bound) {
    int n = bound - origin;
    if (n &gt; 0) {
      return nextInt(n) + origin;
    }
    else {  // range not representable as int
      int r;
      do {
        r = nextInt();
      } while (r &lt; origin || r &gt;= bound);
      return r;
    }
  }</code>

Parameters
randomNumberOrigin	Int: the origin (inclusive) of each random value
randomNumberBound	Int: the bound (exclusive) of each random value

Return
IntStream!	a stream of pseudorandom int values, each with the given origin (inclusive) and bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if randomNumberOrigin is greater than or equal to randomNumberBound

ints

Added in API level 24

fun ints(streamSize: Long): IntStream!

Returns a stream producing the given streamSize number of pseudorandom int values.

A pseudorandom int value is generated as if it's the result of calling the method nextInt().

Parameters
streamSize	Long: the number of values to generate

Return
IntStream!	a stream of pseudorandom int values

Exceptions
java.lang.IllegalArgumentException	if streamSize is less than zero

ints

Added in API level 24

fun ints(
    streamSize: Long, 
    randomNumberOrigin: Int, 
    randomNumberBound: Int
): IntStream!

Returns a stream producing the given streamSize number of pseudorandom int 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:

<code>int nextInt(int origin, int bound) {
    int n = bound - origin;
    if (n &gt; 0) {
      return nextInt(n) + origin;
    }
    else {  // range not representable as int
      int r;
      do {
        r = nextInt();
      } while (r &lt; origin || r &gt;= bound);
      return r;
    }
  }</code>

Parameters
streamSize	Long: the number of values to generate
randomNumberOrigin	Int: the origin (inclusive) of each random value
randomNumberBound	Int: the bound (exclusive) of each random value

Return
IntStream!	a stream of pseudorandom int values, each with the given origin (inclusive) and bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound

longs

Added in API level 24

fun longs(): LongStream!

Returns an effectively unlimited stream of pseudorandom long values.

A pseudorandom long value is generated as if it's the result of calling the method nextLong().

Return
LongStream!	a stream of pseudorandom long values

longs

Added in API level 24

fun longs(streamSize: Long): LongStream!

Returns a stream producing the given streamSize number of pseudorandom long values.

A pseudorandom long value is generated as if it's the result of calling the method nextLong().

Parameters
streamSize	Long: the number of values to generate

Return
LongStream!	a stream of pseudorandom long values

Exceptions
java.lang.IllegalArgumentException	if streamSize is less than zero

longs

Added in API level 24

fun longs(
    randomNumberOrigin: Long, 
    randomNumberBound: Long
): LongStream!

Returns an effectively unlimited stream of pseudorandom long 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:

<code>long nextLong(long origin, long bound) {
    long r = nextLong();
    long n = bound - origin, m = n - 1;
    if ((n &amp; m) == 0L)  // power of two
      r = (r &amp; m) + origin;
    else if (n &gt; 0L) {  // reject over-represented candidates
      for (long u = r &gt;&gt;&gt; 1;            // ensure nonnegative
           u + m - (r = u % n) &lt; 0L;    // rejection check
           u = nextLong() &gt;&gt;&gt; 1) // retry
          ;
      r += origin;
    }
    else {              // range not representable as long
      while (r &lt; origin || r &gt;= bound)
        r = nextLong();
    }
    return r;
  }</code>

Parameters
randomNumberOrigin	Long: the origin (inclusive) of each random value
randomNumberBound	Long: the bound (exclusive) of each random value

Return
LongStream!	a stream of pseudorandom long values, each with the given origin (inclusive) and bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if randomNumberOrigin is greater than or equal to randomNumberBound

longs

Added in API level 24

fun longs(
    streamSize: Long, 
    randomNumberOrigin: Long, 
    randomNumberBound: Long
): LongStream!

Returns a stream producing the given streamSize number of pseudorandom long, 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:

<code>long nextLong(long origin, long bound) {
    long r = nextLong();
    long n = bound - origin, m = n - 1;
    if ((n &amp; m) == 0L)  // power of two
      r = (r &amp; m) + origin;
    else if (n &gt; 0L) {  // reject over-represented candidates
      for (long u = r &gt;&gt;&gt; 1;            // ensure nonnegative
           u + m - (r = u % n) &lt; 0L;    // rejection check
           u = nextLong() &gt;&gt;&gt; 1) // retry
          ;
      r += origin;
    }
    else {              // range not representable as long
      while (r &lt; origin || r &gt;= bound)
        r = nextLong();
    }
    return r;
  }</code>

Parameters
streamSize	Long: the number of values to generate
randomNumberOrigin	Long: the origin (inclusive) of each random value
randomNumberBound	Long: the bound (exclusive) of each random value

Return
LongStream!	a stream of pseudorandom long values, each with the given origin (inclusive) and bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound

nextBoolean

Added in API level 21

fun nextBoolean(): Boolean

Returns the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence. The general contract of nextBoolean is that one boolean value is pseudorandomly generated and returned. The values true and false are produced with (approximately) equal probability.

Return
Boolean	the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence

nextDouble

Added in API level 21

fun nextDouble(): Double

Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.

The general contract of nextDouble is that one double value, chosen (approximately) uniformly from the range 0.0d (inclusive) to 1.0d (exclusive), is pseudorandomly generated and returned.

Return
Double	the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence

nextDouble

Added in API level 21

fun nextDouble(bound: Double): Double

Returns a pseudorandomly chosen double value between zero (inclusive) and the specified bound (exclusive).

Parameters
bound	Double: the upper bound (exclusive) for the returned value. Must be positive and finite

Return
Double	a pseudorandomly chosen double value between zero (inclusive) and the bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if bound is not both positive and finite

nextDouble

Added in API level 21

fun nextDouble(
    origin: Double, 
    bound: Double
): Double

Returns a pseudorandomly chosen double value between the specified origin (inclusive) and the specified bound (exclusive).

Parameters
origin	Double: the least value that can be returned
bound	Double: the upper bound (exclusive) for the returned value

Return
Double	a pseudorandomly chosen double value between the origin (inclusive) and the bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if origin is not finite, or bound is not finite, or origin is greater than or equal to bound

nextFloat

Added in API level 21

fun nextFloat(): Float

Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.

The general contract of nextFloat is that one float value, chosen (approximately) uniformly from the range 0.0f (inclusive) to 1.0f (exclusive), is pseudorandomly generated and returned. All 224 possible float values of the form m x 2-24, where m is a positive integer less than 224, are produced with (approximately) equal probability.

Return
Float	the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence

nextFloat

Added in API level 35

fun nextFloat(bound: Float): Float

Returns a pseudorandomly chosen float value between zero (inclusive) and the specified bound (exclusive).

Parameters
bound	Float: the upper bound (exclusive) for the returned value. Must be positive and finite

Return
Float	a pseudorandomly chosen float value between zero (inclusive) and the bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if bound is not both positive and finite

nextFloat

Added in API level 35

fun nextFloat(
    origin: Float, 
    bound: Float
): Float

Returns a pseudorandomly chosen float value between the specified origin (inclusive) and the specified bound (exclusive).

Parameters
origin	Float: the least value that can be returned
bound	Float: the upper bound (exclusive)

Return
Float	a pseudorandomly chosen float value between the origin (inclusive) and the bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if origin is not finite, or bound is not finite, or origin is greater than or equal to bound

nextInt

Added in API level 21

fun nextInt(): Int

Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence. The general contract of nextInt is that one int value is pseudorandomly generated and returned. All 232 possible int values are produced with (approximately) equal probability.

Return
Int	the next pseudorandom, uniformly distributed int value from this random number generator's sequence

nextInt

Added in API level 21

fun nextInt(bound: Int): Int

Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The general contract of nextInt is that one int value in the specified range is pseudorandomly generated and returned. All bound possible int values are produced with (approximately) equal probability.

Parameters
bound	Int: the upper bound (exclusive). Must be positive.

Return
Int	the next pseudorandom, uniformly distributed int value between zero (inclusive) and bound (exclusive) from this random number generator's sequence

Exceptions
java.lang.IllegalArgumentException	if bound is not positive

nextInt

Added in API level 21

fun nextInt(
    origin: Int, 
    bound: Int
): Int

Returns a pseudorandomly chosen int value between the specified origin (inclusive) and the specified bound (exclusive).

Parameters
origin	Int: the least value that can be returned
bound	Int: the upper bound (exclusive) for the returned value

Return
Int	a pseudorandomly chosen int value between the origin (inclusive) and the bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if origin is greater than or equal to bound

nextLong

Added in API level 21

fun nextLong(): Long

Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence. The general contract of nextLong is that one long value is pseudorandomly generated and returned.

Return
Long	the next pseudorandom, uniformly distributed long value from this random number generator's sequence

nextLong

Added in API level 21

fun nextLong(bound: Long): Long

Returns a pseudorandomly chosen long value between zero (inclusive) and the specified bound (exclusive).

Parameters
bound	Long: the upper bound (exclusive) for the returned value. Must be positive.

Return
Long	a pseudorandomly chosen long value between zero (inclusive) and the bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if bound is not positive

nextLong

Added in API level 21

fun nextLong(
    origin: Long, 
    bound: Long
): Long

Returns a pseudorandomly chosen long value between the specified origin (inclusive) and the specified bound (exclusive).

Parameters
origin	Long: the least value that can be returned
bound	Long: the upper bound (exclusive) for the returned value

Return
Long	a pseudorandomly chosen long value between the origin (inclusive) and the bound (exclusive)

Exceptions
java.lang.IllegalArgumentException	if origin is greater than or equal to bound

setSeed

Added in API level 21

fun setSeed(seed: Long): Unit

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

Parameters
seed	Long: the initial seed

Exceptions
java.lang.UnsupportedOperationException	always

Protected methods

next

Added in API level 21

protected fun next(bits: Int): Int

Generates a pseudorandom number with the indicated number of low-order bits. Because this class has no subclasses, this method cannot be invoked or overridden.

Parameters
bits	Int: random bits

Return
Int	the next pseudorandom value from this random number generator's sequence