Serializable
, RandomGenerator
public final class ThreadLocalRandom extends Random
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 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 SecureRandom
in security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless the system property java.util.secureRandomSeed
is set to true
.
RandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator
Modifier and Type | Method | Description |
---|---|---|
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 |
Returns an effectively unlimited stream of pseudorandom
double values, each conforming to the given origin (inclusive) and bound (exclusive). |
DoubleStream |
doubles |
Returns a stream producing the given streamSize number of pseudorandom double values, each between zero (inclusive) and one (exclusive). |
DoubleStream |
doubles |
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 |
Returns an effectively unlimited stream of pseudorandom
int values, each conforming to the given origin (inclusive) and bound (exclusive). |
IntStream |
ints |
Returns a stream producing the given streamSize number of pseudorandom int values. |
IntStream |
ints |
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 |
Returns a stream producing the given streamSize number of pseudorandom long values. |
LongStream |
longs |
Returns an effectively unlimited stream of pseudorandom
long values, each conforming to the given origin (inclusive) and bound (exclusive). |
LongStream |
longs |
Returns a stream producing the given streamSize number of pseudorandom long , each conforming to the given origin (inclusive) and bound (exclusive). |
protected int |
next |
Generates a pseudorandom number with the indicated number of low-order bits. |
double |
nextDouble |
Returns a pseudorandomly chosen double value between zero (inclusive) and the specified bound (exclusive). |
double |
nextDouble |
Returns a pseudorandomly chosen double value between the specified origin (inclusive) and the specified bound (exclusive). |
float |
nextFloat |
Returns a pseudorandomly chosen float value between zero (inclusive) and the specified bound (exclusive). |
float |
nextFloat |
Returns a pseudorandomly chosen float value between the specified origin (inclusive) and the specified bound (exclusive). |
int |
nextInt |
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 |
Returns a pseudorandomly chosen int value between the specified origin (inclusive) and the specified bound (exclusive). |
long |
nextLong |
Returns a pseudorandomly chosen long value between zero (inclusive) and the specified bound (exclusive). |
long |
nextLong |
Returns a pseudorandomly chosen long value between the specified origin (inclusive) and the specified bound (exclusive). |
void |
setSeed |
Throws UnsupportedOperationException . |
from, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextLong
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
isDeprecated, nextExponential, nextGaussian
public static ThreadLocalRandom current()
ThreadLocalRandom
object. Methods of this object should be called only by the current thread, not by other threads.ThreadLocalRandom
public void setSeed(long seed)
UnsupportedOperationException
. Setting seeds in this generator is not supported.setSeed
in class Random
seed
- the seed valueUnsupportedOperationException
- alwaysprotected int next(int bits)
public int nextInt(int bound)
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.nextInt
in interface RandomGenerator
nextInt
in class Random
bound
- the upper bound (exclusive). Must be positive.int
value between zero (inclusive) and bound
(exclusive) from this random number generator's sequenceIllegalArgumentException
- if bound is not positivepublic int nextInt(int origin, int bound)
int
value between the specified origin (inclusive) and the specified bound (exclusive).origin
- the least value that can be returnedbound
- the upper bound (exclusive) for the returned valueint
value between the origin (inclusive) and the bound (exclusive)IllegalArgumentException
- if origin
is greater than or equal to bound
public long nextLong(long bound)
long
value between zero (inclusive) and the specified bound (exclusive).bound
- the upper bound (exclusive) for the returned value. Must be positive.long
value between zero (inclusive) and the bound (exclusive)IllegalArgumentException
- if bound
is not positivepublic long nextLong(long origin, long bound)
long
value between the specified origin (inclusive) and the specified bound (exclusive).origin
- the least value that can be returnedbound
- the upper bound (exclusive) for the returned valuelong
value between the origin (inclusive) and the bound (exclusive)IllegalArgumentException
- if origin
is greater than or equal to bound
public float nextFloat(float bound)
float
value between zero (inclusive) and the specified bound (exclusive).bound
- the upper bound (exclusive) for the returned value. Must be positive and finitefloat
value between zero (inclusive) and the bound (exclusive)IllegalArgumentException
- if bound
is not both positive and finitepublic float nextFloat(float origin, float bound)
float
value between the specified origin (inclusive) and the specified bound (exclusive).origin
- the least value that can be returnedbound
- the upper bound (exclusive)float
value between the origin (inclusive) and the bound (exclusive)IllegalArgumentException
- if origin
is not finite, or bound
is not finite, or origin
is greater than or equal to bound
public double nextDouble(double bound)
double
value between zero (inclusive) and the specified bound (exclusive).bound
- the upper bound (exclusive) for the returned value. Must be positive and finitedouble
value between zero (inclusive) and the bound (exclusive)IllegalArgumentException
- if bound
is not both positive and finitepublic double nextDouble(double origin, double bound)
double
value between the specified origin (inclusive) and the specified bound (exclusive).origin
- the least value that can be returnedbound
- the upper bound (exclusive) for the returned valuedouble
value between the origin (inclusive) and the bound (exclusive)IllegalArgumentException
- if origin
is not finite, or bound
is not finite, or origin
is greater than or equal to bound
public IntStream ints(long streamSize)
streamSize
number of pseudorandom int
values. A pseudorandom int
value is generated as if it's the result of calling the method Random.nextInt()
.
ints
in interface RandomGenerator
ints
in class Random
streamSize
- the number of values to generateint
valuesIllegalArgumentException
- if streamSize
is less than zeropublic IntStream ints()
int
values. A pseudorandom int
value is generated as if it's the result of calling the method Random.nextInt()
.
ints
in interface RandomGenerator
ints
in class Random
ints(Long.MAX_VALUE)
.int
valuespublic IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound)
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:
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;
}
}
ints
in interface RandomGenerator
ints
in class Random
streamSize
- the number of values to generaterandomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- the bound (exclusive) of each random valueint
values, each with the given origin (inclusive) and bound (exclusive)IllegalArgumentException
- if streamSize
is less than zero, or randomNumberOrigin
is greater than or equal to randomNumberBound
public IntStream ints(int randomNumberOrigin, int randomNumberBound)
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:
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;
}
}
ints
in interface RandomGenerator
ints
in class Random
ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
.randomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- the bound (exclusive) of each random valueint
values, each with the given origin (inclusive) and bound (exclusive)IllegalArgumentException
- if randomNumberOrigin
is greater than or equal to randomNumberBound
public LongStream longs(long streamSize)
streamSize
number of pseudorandom long
values. A pseudorandom long
value is generated as if it's the result of calling the method Random.nextLong()
.
longs
in interface RandomGenerator
longs
in class Random
streamSize
- the number of values to generatelong
valuesIllegalArgumentException
- if streamSize
is less than zeropublic LongStream longs()
long
values. A pseudorandom long
value is generated as if it's the result of calling the method Random.nextLong()
.
longs
in interface RandomGenerator
longs
in class Random
longs(Long.MAX_VALUE)
.long
valuespublic LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound)
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:
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;
}
longs
in interface RandomGenerator
longs
in class Random
streamSize
- the number of values to generaterandomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- the bound (exclusive) of each random valuelong
values, each with the given origin (inclusive) and bound (exclusive)IllegalArgumentException
- if streamSize
is less than zero, or randomNumberOrigin
is greater than or equal to randomNumberBound
public LongStream longs(long randomNumberOrigin, long randomNumberBound)
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:
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;
}
longs
in interface RandomGenerator
longs
in class Random
longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
.randomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- the bound (exclusive) of each random valuelong
values, each with the given origin (inclusive) and bound (exclusive)IllegalArgumentException
- if randomNumberOrigin
is greater than or equal to randomNumberBound
public DoubleStream doubles(long streamSize)
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 Random.nextDouble()
.
doubles
in interface RandomGenerator
doubles
in class Random
streamSize
- the number of values to generatedouble
valuesIllegalArgumentException
- if streamSize
is less than zeropublic DoubleStream doubles()
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 Random.nextDouble()
.
doubles
in interface RandomGenerator
doubles
in class Random
doubles(Long.MAX_VALUE)
.double
valuespublic DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)
streamSize
number of pseudorandom double
values, each conforming to the given origin (inclusive) and bound (exclusive).doubles
in interface RandomGenerator
doubles
in class Random
streamSize
- the number of values to generaterandomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- the bound (exclusive) of each random valuedouble
values, each with the given origin (inclusive) and bound (exclusive)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
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
double
values, each conforming to the given origin (inclusive) and bound (exclusive).doubles
in interface RandomGenerator
doubles
in class Random
doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
.randomNumberOrigin
- the origin (inclusive) of each random valuerandomNumberBound
- the bound (exclusive) of each random valuedouble
values, each with the given origin (inclusive) and bound (exclusive)IllegalArgumentException
- if randomNumberOrigin
is not finite, or randomNumberBound
is not finite, or randomNumberOrigin
is greater than or equal to randomNumberBound
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Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/concurrent/ThreadLocalRandom.html