Class ThreadLocalRandom
 java.lang.Object

 java.util.Random

 java.util.concurrent.ThreadLocalRandom
 All Implemented Interfaces:
Serializable
public class ThreadLocalRandom extends Random
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 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 securitysensitive applications. Additionally, defaultconstructed instances do not use a cryptographically random seed unless the system property java.util.secureRandomSeed
is set to true
.
 Since:
 1.7
 See Also:
 Serialized Form
Method Summary
Modifier and Type  Method  Description 

static ThreadLocalRandom  current()  Returns the current thread's 
DoubleStream  doubles()  Returns an effectively unlimited stream of pseudorandom 
DoubleStream  doubles(double randomNumberOrigin,
double randomNumberBound)  Returns an effectively unlimited stream of pseudorandom 
DoubleStream  doubles(long streamSize)  Returns a stream producing the given 
DoubleStream  doubles(long streamSize,
double randomNumberOrigin,
double randomNumberBound)  Returns a stream producing the given 
IntStream  ints()  Returns an effectively unlimited stream of pseudorandom 
IntStream  ints(int randomNumberOrigin,
int randomNumberBound)  Returns an effectively unlimited stream of pseudorandom 
IntStream  ints(long streamSize)  Returns a stream producing the given 
IntStream  ints(long streamSize,
int randomNumberOrigin,
int randomNumberBound)  Returns a stream producing the given 
LongStream  longs()  Returns an effectively unlimited stream of pseudorandom 
LongStream  longs(long streamSize)  Returns a stream producing the given 
LongStream  longs(long randomNumberOrigin,
long randomNumberBound)  Returns an effectively unlimited stream of pseudorandom 
LongStream  longs(long streamSize,
long randomNumberOrigin,
long randomNumberBound)  Returns a stream producing the given 
protected int  next(int bits)  Generates a pseudorandom number with the indicated number of loworder bits. 
boolean  nextBoolean()  Returns a pseudorandom 
double  nextDouble()  Returns a pseudorandom 
double  nextDouble(double bound)  Returns a pseudorandom 
double  nextDouble(double origin,
double bound)  Returns a pseudorandom 
float  nextFloat()  Returns a pseudorandom 
int  nextInt()  Returns a pseudorandom 
int  nextInt(int bound)  Returns a pseudorandom 
int  nextInt(int origin,
int bound)  Returns a pseudorandom 
long  nextLong()  Returns a pseudorandom 
long  nextLong(long bound)  Returns a pseudorandom 
long  nextLong(long origin,
long bound)  Returns a pseudorandom 
void  setSeed(long seed)  Throws 
Methods declared in class java.util.Random
nextBytes, nextGaussian
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Method Detail
current
public static ThreadLocalRandom current()
Returns the current thread's ThreadLocalRandom
.
 Returns:
 the current thread's
ThreadLocalRandom
setSeed
public void setSeed(long seed)
Throws UnsupportedOperationException
. Setting seeds in this generator is not supported.
 Overrides:

setSeed
in classRandom
 Parameters:

seed
 the initial seed  Throws:

UnsupportedOperationException
 always
next
protected int next(int bits)
Generates a pseudorandom number with the indicated number of loworder bits. Because this class has no subclasses, this method cannot be invoked or overridden.
 Overrides:

next
in classRandom
 Parameters:

bits
 random bits  Returns:
 the next pseudorandom value from this random number generator's sequence
nextInt
public int nextInt()
Returns a pseudorandom int
value.
nextInt
public int nextInt(int bound)
Returns a pseudorandom int
value between zero (inclusive) and the specified bound (exclusive).
 Overrides:

nextInt
in classRandom
 Parameters:

bound
 the upper bound (exclusive). Must be positive.  Returns:
 a pseudorandom
int
value between zero (inclusive) and the bound (exclusive)  Throws:

IllegalArgumentException
 ifbound
is not positive
nextInt
public int nextInt(int origin, int bound)
Returns a pseudorandom int
value between the specified origin (inclusive) and the specified bound (exclusive).
 Parameters:

origin
 the least value returned 
bound
 the upper bound (exclusive)  Returns:
 a pseudorandom
int
value between the origin (inclusive) and the bound (exclusive)  Throws:

IllegalArgumentException
 iforigin
is greater than or equal tobound
nextLong
public long nextLong()
Returns a pseudorandom long
value.
nextLong
public long nextLong(long bound)
Returns a pseudorandom long
value between zero (inclusive) and the specified bound (exclusive).
 Parameters:

bound
 the upper bound (exclusive). Must be positive.  Returns:
 a pseudorandom
long
value between zero (inclusive) and the bound (exclusive)  Throws:

IllegalArgumentException
 ifbound
is not positive
nextLong
public long nextLong(long origin, long bound)
Returns a pseudorandom long
value between the specified origin (inclusive) and the specified bound (exclusive).
 Parameters:

origin
 the least value returned 
bound
 the upper bound (exclusive)  Returns:
 a pseudorandom
long
value between the origin (inclusive) and the bound (exclusive)  Throws:

IllegalArgumentException
 iforigin
is greater than or equal tobound
nextDouble
public double nextDouble()
Returns a pseudorandom double
value between zero (inclusive) and one (exclusive).
 Overrides:

nextDouble
in classRandom
 Returns:
 a pseudorandom
double
value between zero (inclusive) and one (exclusive)  See Also:
Math.random()
nextDouble
public double nextDouble(double bound)
Returns a pseudorandom double
value between 0.0 (inclusive) and the specified bound (exclusive).
 Parameters:

bound
 the upper bound (exclusive). Must be positive.  Returns:
 a pseudorandom
double
value between zero (inclusive) and the bound (exclusive)  Throws:

IllegalArgumentException
 ifbound
is not positive
nextDouble
public double nextDouble(double origin, double bound)
Returns a pseudorandom double
value between the specified origin (inclusive) and bound (exclusive).
 Parameters:

origin
 the least value returned 
bound
 the upper bound (exclusive)  Returns:
 a pseudorandom
double
value between the origin (inclusive) and the bound (exclusive)  Throws:

IllegalArgumentException
 iforigin
is greater than or equal tobound
nextBoolean
public boolean nextBoolean()
Returns a pseudorandom boolean
value.
 Overrides:

nextBoolean
in classRandom
 Returns:
 a pseudorandom
boolean
value
nextFloat
public float nextFloat()
Returns a pseudorandom float
value between zero (inclusive) and one (exclusive).
 Overrides:

nextFloat
in classRandom
 Returns:
 a pseudorandom
float
value between zero (inclusive) and one (exclusive)
ints
public IntStream ints(long streamSize)
Returns a stream producing the given streamSize
number of pseudorandom int
values.
 Overrides:

ints
in classRandom
 Parameters:

streamSize
 the number of values to generate  Returns:
 a stream of pseudorandom
int
values  Throws:

IllegalArgumentException
 ifstreamSize
is less than zero  Since:
 1.8
ints
public IntStream ints()
Returns an effectively unlimited stream of pseudorandom int
values.
 Overrides:

ints
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
ints(Long.MAX_VALUE)
.  Returns:
 a stream of pseudorandom
int
values  Since:
 1.8
ints
public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound)
Returns a stream producing the given streamSize
number of pseudorandom int
values, each conforming to the given origin (inclusive) and bound (exclusive).
 Overrides:

ints
in classRandom
 Parameters:

streamSize
 the number of values to generate 
randomNumberOrigin
 the origin (inclusive) of each random value 
randomNumberBound
 the bound (exclusive) of each random value  Returns:
 a stream of pseudorandom
int
values, each with the given origin (inclusive) and bound (exclusive)  Throws:

IllegalArgumentException
 ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8
ints
public IntStream ints(int randomNumberOrigin, int randomNumberBound)
Returns an effectively unlimited stream of pseudorandom
int
values, each conforming to the given origin (inclusive) and bound (exclusive).
 Overrides:

ints
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
.  Parameters:

randomNumberOrigin
 the origin (inclusive) of each random value 
randomNumberBound
 the bound (exclusive) of each random value  Returns:
 a stream of pseudorandom
int
values, each with the given origin (inclusive) and bound (exclusive)  Throws:

IllegalArgumentException
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8
longs
public LongStream longs(long streamSize)
Returns a stream producing the given streamSize
number of pseudorandom long
values.
 Overrides:

longs
in classRandom
 Parameters:

streamSize
 the number of values to generate  Returns:
 a stream of pseudorandom
long
values  Throws:

IllegalArgumentException
 ifstreamSize
is less than zero  Since:
 1.8
longs
public LongStream longs()
Returns an effectively unlimited stream of pseudorandom long
values.
 Overrides:

longs
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
longs(Long.MAX_VALUE)
.  Returns:
 a stream of pseudorandom
long
values  Since:
 1.8
longs
public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound)
Returns a stream producing the given streamSize
number of pseudorandom long
, each conforming to the given origin (inclusive) and bound (exclusive).
 Overrides:

longs
in classRandom
 Parameters:

streamSize
 the number of values to generate 
randomNumberOrigin
 the origin (inclusive) of each random value 
randomNumberBound
 the bound (exclusive) of each random value  Returns:
 a stream of pseudorandom
long
values, each with the given origin (inclusive) and bound (exclusive)  Throws:

IllegalArgumentException
 ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8
longs
public LongStream longs(long randomNumberOrigin, long randomNumberBound)
Returns an effectively unlimited stream of pseudorandom
long
values, each conforming to the given origin (inclusive) and bound (exclusive).
 Overrides:

longs
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
.  Parameters:

randomNumberOrigin
 the origin (inclusive) of each random value 
randomNumberBound
 the bound (exclusive) of each random value  Returns:
 a stream of pseudorandom
long
values, each with the given origin (inclusive) and bound (exclusive)  Throws:

IllegalArgumentException
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8
doubles
public DoubleStream doubles(long streamSize)
Returns a stream producing the given streamSize
number of pseudorandom double
values, each between zero (inclusive) and one (exclusive).
 Overrides:

doubles
in classRandom
 Parameters:

streamSize
 the number of values to generate  Returns:
 a stream of
double
values  Throws:

IllegalArgumentException
 ifstreamSize
is less than zero  Since:
 1.8
doubles
public DoubleStream doubles()
Returns an effectively unlimited stream of pseudorandom
double
values, each between zero (inclusive) and one (exclusive).
 Overrides:

doubles
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
doubles(Long.MAX_VALUE)
.  Returns:
 a stream of pseudorandom
double
values  Since:
 1.8
doubles
public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)
Returns a stream producing the given streamSize
number of pseudorandom double
values, each conforming to the given origin (inclusive) and bound (exclusive).
 Overrides:

doubles
in classRandom
 Parameters:

streamSize
 the number of values to generate 
randomNumberOrigin
 the origin (inclusive) of each random value 
randomNumberBound
 the bound (exclusive) of each random value  Returns:
 a stream of pseudorandom
double
values, each with the given origin (inclusive) and bound (exclusive)  Throws:

IllegalArgumentException
 ifstreamSize
is less than zero, orrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8
doubles
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
Returns an effectively unlimited stream of pseudorandom
double
values, each conforming to the given origin (inclusive) and bound (exclusive).
 Overrides:

doubles
in classRandom
 Implementation Note:
 This method is implemented to be equivalent to
doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)
.  Parameters:

randomNumberOrigin
 the origin (inclusive) of each random value 
randomNumberBound
 the bound (exclusive) of each random value  Returns:
 a stream of pseudorandom
double
values, each with the given origin (inclusive) and bound (exclusive)  Throws:

IllegalArgumentException
 ifrandomNumberOrigin
is greater than or equal torandomNumberBound
 Since:
 1.8