Random
open class Random : RandomGenerator, Serializable
kotlin.Any | |
↳ | java.util.Random |
An instance of this class is used to generate a stream of pseudorandom numbers; its period is only 248. The class uses a 48-bit seed, which is modified using a linear congruential formula. (See Donald E. Knuth, The Art of Computer Programming, Volume 2, Third edition: Seminumerical Algorithms, Section 3.2.1.)
If two instances of Random
are created with the same seed, and the same sequence of method calls is made for each, they will generate and return identical sequences of numbers. In order to guarantee this property, particular algorithms are specified for the class Random
. Java implementations must use all the algorithms shown here for the class Random
, for the sake of absolute portability of Java code. However, subclasses of class Random
are permitted to use other algorithms, so long as they adhere to the general contracts for all the methods.
The algorithms implemented by class Random
use a protected
utility method that on each invocation can supply up to 32 pseudorandomly generated bits.
Many applications will find the method Math.random
simpler to use.
Instances of java.util.Random
are threadsafe. However, the concurrent use of the same java.util.Random
instance across threads may encounter contention and consequent poor performance. Consider instead using java.util.concurrent.ThreadLocalRandom
in multithreaded designs.
Instances of java.util.Random
are not cryptographically secure. Consider instead using java.security.SecureRandom
to get a cryptographically secure pseudo-random number generator for use by security-sensitive applications.
Summary
Public constructors | |
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Random() Creates a new random number generator. |
|
Creates a new random number generator using a single |
Public methods | |
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open DoubleStream! |
doubles() Returns an effectively unlimited stream of pseudorandom |
open DoubleStream! |
Returns an effectively unlimited stream of pseudorandom |
open DoubleStream! |
Returns a stream producing the given |
open DoubleStream! |
Returns a stream producing the given |
open static Random! |
from(generator: RandomGenerator!) Returns an instance of |
open IntStream! |
ints() Returns an effectively unlimited stream of pseudorandom |
open IntStream! |
Returns an effectively unlimited stream of pseudorandom |
open IntStream! |
Returns a stream producing the given |
open IntStream! |
Returns a stream producing the given |
open LongStream! |
longs() Returns an effectively unlimited stream of pseudorandom |
open LongStream! |
Returns a stream producing the given |
open LongStream! |
Returns an effectively unlimited stream of pseudorandom |
open LongStream! |
Returns a stream producing the given |
open Boolean |
Returns the next pseudorandom, uniformly distributed |
open Unit |
Generates random bytes and places them into a user-supplied byte array. |
open Double |
Returns the next pseudorandom, uniformly distributed |
open Float |
Returns the next pseudorandom, uniformly distributed |
open Double |
Returns the next pseudorandom, Gaussian ("normally") distributed |
open Int |
nextInt() Returns the next pseudorandom, uniformly distributed |
open Int |
Returns a pseudorandom, uniformly distributed |
open Long |
nextLong() Returns the next pseudorandom, uniformly distributed |
open Unit |
Sets or updates the seed of this random number generator using the provided |
Protected methods | |
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open Int |
Generates the next pseudorandom number. |
Inherited functions | |
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Public constructors
Random
Random()
Creates a new random number generator. This constructor sets the seed of the random number generator to a value very likely to be distinct from any other invocation of this constructor.
Random
Random(seed: Long)
Creates a new random number generator using a single long
seed. The seed is the initial value of the internal state of the pseudorandom number generator which is maintained by method next
.
Parameters | |
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seed |
Long: the initial seed |
See Also
Public methods
doubles
open 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 | |
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DoubleStream! |
a stream of pseudorandom double values |
doubles
open 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).
Parameters | |
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randomNumberOrigin |
Double: the origin (inclusive) of each random value |
randomNumberBound |
Double: the bound (exclusive) of each random value |
Return | |
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DoubleStream! |
a stream of pseudorandom double values, each with the given origin (inclusive) and bound (exclusive) |
Exceptions | |
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java.lang.IllegalArgumentException |
if randomNumberOrigin is not finite, or randomNumberBound is not finite, or randomNumberOrigin is greater than or equal to randomNumberBound |
doubles
open 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 | |
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streamSize |
Long: the number of values to generate |
Return | |
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DoubleStream! |
a stream of double values |
Exceptions | |
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java.lang.IllegalArgumentException |
if streamSize is less than zero |
doubles
open 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).
Parameters | |
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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 | |
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DoubleStream! |
a stream of pseudorandom double values, each with the given origin (inclusive) and bound (exclusive) |
Exceptions | |
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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 |
from
open static fun from(generator: RandomGenerator!): Random!
Returns an instance of Random
that delegates method calls to the RandomGenerator
argument. If the generator is an instance of Random
, it is returned. Otherwise, this method returns an instance of Random
that delegates all methods except setSeed
to the generator. The returned instance's setSeed
method always throws UnsupportedOperationException
. The returned instance is not serializable.
Parameters | |
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generator |
RandomGenerator!: the RandomGenerator calls are delegated to |
Return | |
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Random! |
the delegating Random instance |
Exceptions | |
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java.lang.NullPointerException |
if generator is null |
ints
open 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 | |
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IntStream! |
a stream of pseudorandom int values |
ints
open 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 > 0) { return nextInt(n) + origin; } else { // range not representable as int int r; do { r = nextInt(); } while (r < origin || r >= bound); return r; } }</code>
Parameters | |
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randomNumberOrigin |
Int: the origin (inclusive) of each random value |
randomNumberBound |
Int: the bound (exclusive) of each random value |
Return | |
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IntStream! |
a stream of pseudorandom int values, each with the given origin (inclusive) and bound (exclusive) |
Exceptions | |
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java.lang.IllegalArgumentException |
if randomNumberOrigin is greater than or equal to randomNumberBound |
ints
open 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 | |
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streamSize |
Long: the number of values to generate |
Return | |
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IntStream! |
a stream of pseudorandom int values |
Exceptions | |
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java.lang.IllegalArgumentException |
if streamSize is less than zero |
ints
open 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 > 0) { return nextInt(n) + origin; } else { // range not representable as int int r; do { r = nextInt(); } while (r < origin || r >= bound); return r; } }</code>
Parameters | |
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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 | |
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IntStream! |
a stream of pseudorandom int values, each with the given origin (inclusive) and bound (exclusive) |
Exceptions | |
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java.lang.IllegalArgumentException |
if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound |
longs
open 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 | |
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LongStream! |
a stream of pseudorandom long values |
longs
open 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 | |
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streamSize |
Long: the number of values to generate |
Return | |
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LongStream! |
a stream of pseudorandom long values |
Exceptions | |
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java.lang.IllegalArgumentException |
if streamSize is less than zero |
longs
open 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 & m) == 0L) // power of two r = (r & m) + origin; else if (n > 0L) { // reject over-represented candidates for (long u = r >>> 1; // ensure nonnegative u + m - (r = u % n) < 0L; // rejection check u = nextLong() >>> 1) // retry ; r += origin; } else { // range not representable as long while (r < origin || r >= bound) r = nextLong(); } return r; }</code>
Parameters | |
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randomNumberOrigin |
Long: the origin (inclusive) of each random value |
randomNumberBound |
Long: the bound (exclusive) of each random value |
Return | |
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LongStream! |
a stream of pseudorandom long values, each with the given origin (inclusive) and bound (exclusive) |
Exceptions | |
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java.lang.IllegalArgumentException |
if randomNumberOrigin is greater than or equal to randomNumberBound |
longs
open 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 & m) == 0L) // power of two r = (r & m) + origin; else if (n > 0L) { // reject over-represented candidates for (long u = r >>> 1; // ensure nonnegative u + m - (r = u % n) < 0L; // rejection check u = nextLong() >>> 1) // retry ; r += origin; } else { // range not representable as long while (r < origin || r >= bound) r = nextLong(); } return r; }</code>
Parameters | |
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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 | |
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LongStream! |
a stream of pseudorandom long values, each with the given origin (inclusive) and bound (exclusive) |
Exceptions | |
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java.lang.IllegalArgumentException |
if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound |
nextBoolean
open 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 | |
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Boolean |
the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence |
nextBytes
open fun nextBytes(bytes: ByteArray!): Unit
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.
Parameters | |
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bytes |
ByteArray!: the byte array to fill with random bytes |
Exceptions | |
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java.lang.NullPointerException |
if the byte array is null |
nextDouble
open 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 | |
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Double |
the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence |
See Also
nextFloat
open 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 | |
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Float |
the next pseudorandom, uniformly distributed float value between 0.0f and 1.0f from this random number generator's sequence |
nextGaussian
open fun nextGaussian(): Double
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.
Return | |
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Double |
the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence |
nextInt
open 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 | |
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Int |
the next pseudorandom, uniformly distributed int value from this random number generator's sequence |
nextInt
open 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 | |
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bound |
Int: the upper bound (exclusive). Must be positive. |
Return | |
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Int |
the next pseudorandom, uniformly distributed int value between zero (inclusive) and bound (exclusive) from this random number generator's sequence |
Exceptions | |
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java.lang.IllegalArgumentException |
if bound is not positive |
nextLong
open 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 | |
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Long |
the next pseudorandom, uniformly distributed long value from this random number generator's sequence |
setSeed
open fun setSeed(seed: Long): Unit
Sets or updates the seed of this random number generator using the provided long
seed value (optional operation).
Parameters | |
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seed |
Long: the seed value |
Exceptions | |
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java.lang.UnsupportedOperationException |
if the setSeed operation is not supported by this random number generator |
Protected methods
next
protected open fun next(bits: Int): Int
Generates the next pseudorandom number. This method returns an int
value such that, 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
.
Parameters | |
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bits |
Int: random bits |
Return | |
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Int |
the next pseudorandom value from this random number generator's sequence |