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

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