public class ThreadLocalRandom
extends java.util.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
accidently share a ThreadLocalRandom
across multiple threads.
This class also provides additional commonly used bounded random generation methods.
Modifier and Type | Field and Description |
---|---|
private static long |
addend |
(package private) boolean |
initialized
Initialization flag to permit calls to setSeed to succeed only
while executing the Random constructor.
|
private static java.lang.ThreadLocal<ThreadLocalRandom> |
localRandom
The actual ThreadLocal
|
private static long |
mask |
private static long |
multiplier |
private long |
pad0 |
private long |
pad1 |
private long |
pad2 |
private long |
pad3 |
private long |
pad4 |
private long |
pad5 |
private long |
pad6 |
private long |
pad7 |
private long |
rnd
The random seed.
|
private static long |
serialVersionUID |
Constructor and Description |
---|
ThreadLocalRandom()
Constructor called only by localRandom.initialValue.
|
Modifier and Type | Method and Description |
---|---|
static ThreadLocalRandom |
current()
Returns the current thread's
ThreadLocalRandom . |
protected int |
next(int bits) |
double |
nextDouble(double n)
Returns a pseudorandom, uniformly distributed
double value
between 0 (inclusive) and the specified value (exclusive). |
double |
nextDouble(double least,
double bound)
Returns a pseudorandom, uniformly distributed value between the
given least value (inclusive) and bound (exclusive).
|
int |
nextInt(int least,
int bound)
Returns a pseudorandom, uniformly distributed value between the
given least value (inclusive) and bound (exclusive).
|
long |
nextLong(long n)
Returns a pseudorandom, uniformly distributed value
between 0 (inclusive) and the specified value (exclusive).
|
long |
nextLong(long least,
long bound)
Returns a pseudorandom, uniformly distributed value between the
given least value (inclusive) and bound (exclusive).
|
void |
setSeed(long seed)
Throws
UnsupportedOperationException . |
private static final long multiplier
private static final long addend
private static final long mask
private long rnd
boolean initialized
private long pad0
private long pad1
private long pad2
private long pad3
private long pad4
private long pad5
private long pad6
private long pad7
private static final java.lang.ThreadLocal<ThreadLocalRandom> localRandom
private static final long serialVersionUID
ThreadLocalRandom()
public static ThreadLocalRandom current()
ThreadLocalRandom
.ThreadLocalRandom
public void setSeed(long seed)
UnsupportedOperationException
. Setting seeds in
this generator is not supported.setSeed
in class java.util.Random
java.lang.UnsupportedOperationException
- alwaysprotected int next(int bits)
next
in class java.util.Random
public int nextInt(int least, int bound)
least
- the least value returnedbound
- the upper bound (exclusive)java.lang.IllegalArgumentException
- if least greater than or equal
to boundpublic long nextLong(long n)
n
- the bound on the random number to be returned. Must be
positive.java.lang.IllegalArgumentException
- if n is not positivepublic long nextLong(long least, long bound)
least
- the least value returnedbound
- the upper bound (exclusive)java.lang.IllegalArgumentException
- if least greater than or equal
to boundpublic double nextDouble(double n)
double
value
between 0 (inclusive) and the specified value (exclusive).n
- the bound on the random number to be returned. Must be
positive.java.lang.IllegalArgumentException
- if n is not positivepublic double nextDouble(double least, double bound)
least
- the least value returnedbound
- the upper bound (exclusive)java.lang.IllegalArgumentException
- if least greater than or equal
to bound