Package io.netty.util.internal

Class ThreadLocalRandom

java.lang.Object
java.util.Random
io.netty.util.internal.ThreadLocalRandom
All Implemented Interfaces:
Serializable, java.util.random.RandomGenerator
public final 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
invalid reference 
io.netty.util.internal.chmv8.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. //since 1.7 //author Doug Lea

See Also:

  • Nested Class Summary

    Nested classes/interfaces inherited from interface java.util.random.RandomGenerator

    java.util.random.RandomGenerator.ArbitrarilyJumpableGenerator, java.util.random.RandomGenerator.JumpableGenerator, java.util.random.RandomGenerator.LeapableGenerator, java.util.random.RandomGenerator.SplittableGenerator, java.util.random.RandomGenerator.StreamableGenerator

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private static final long
    addend
     
    (package private) boolean
    initialized
    Initialization flag to permit calls to setSeed to succeed only while executing the Random constructor.
    private static long
    initialSeedUniquifier
     
    private static final InternalLogger
    logger
     
    private static final long
    mask
     
    private static final 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
    seedGeneratorEndTime
     
    private static final long
    seedGeneratorStartTime
     
    private static final Thread
    seedGeneratorThread
     
    private static final BlockingQueue<Long>
    seedQueue
     
    private static final AtomicLong
    seedUniquifier
     
    private static final long
    serialVersionUID
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    ThreadLocalRandom()
    Constructor called only by localRandom.initialValue.

  • Method Summary

    Modifier and Type
    Method
    Description
    static ThreadLocalRandom
    current()
    Returns the current thread's ThreadLocalRandom.
    static long
    getInitialSeedUniquifier()
     
    private static long
    mix64(long z)
     
    private static long
    newSeed()
     
    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).
    static void
    setInitialSeedUniquifier(long initialSeedUniquifier)
     
    void
    setSeed(long seed)
    Throws UnsupportedOperationException.

    Methods inherited from class java.util.Random

    doubles, doubles, doubles, doubles, from, ints, ints, ints, ints, longs, longs, longs, longs, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLong

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface java.util.random.RandomGenerator

    isDeprecated, nextExponential, nextFloat, nextFloat, nextGaussian

  • Field Details

    • logger

      private static final InternalLogger logger

    • seedUniquifier

      private static final AtomicLong seedUniquifier

    • initialSeedUniquifier

      private static volatile long initialSeedUniquifier

    • seedGeneratorThread

      private static final Thread seedGeneratorThread

    • seedQueue

      private static final BlockingQueue<Long> seedQueue

    • seedGeneratorStartTime

      private static final long seedGeneratorStartTime

    • seedGeneratorEndTime

      private static volatile long seedGeneratorEndTime

    • multiplier

      private static final long multiplier
      See Also:

    • addend

      private static final long addend
      See Also:

    • mask

      private static final long mask
      See Also:

    • rnd

      private long rnd
      The random seed. We can't use super.seed.

    • initialized

      boolean initialized
      Initialization flag to permit calls to setSeed to succeed only while executing the Random constructor. We can't allow others since it would cause setting seed in one part of a program to unintentionally impact other usages by the thread.

    • pad0

      private long pad0

    • pad1

      private long pad1

    • pad2

      private long pad2

    • pad3

      private long pad3

    • pad4

      private long pad4

    • pad5

      private long pad5

    • pad6

      private long pad6

    • pad7

      private long pad7

    • serialVersionUID

      private static final long serialVersionUID
      See Also:

  • Constructor Details

    • ThreadLocalRandom

      ThreadLocalRandom()
      Constructor called only by localRandom.initialValue.

  • Method Details

    • setInitialSeedUniquifier

      public static void setInitialSeedUniquifier(long initialSeedUniquifier)

    • getInitialSeedUniquifier

      public static long getInitialSeedUniquifier()

    • newSeed

      private static long newSeed()

    • mix64

      private static long mix64(long z)

    • 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 class Random
      Throws:
      UnsupportedOperationException - always

    • next

      protected int next(int bits)
      Overrides:
      next in class Random

    • nextInt

      public int nextInt(int least, int bound)
      Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).
      Parameters:
      least - the least value returned
      bound - the upper bound (exclusive)
      Returns:
      the next value
      Throws:
      IllegalArgumentException - if least greater than or equal to bound

    • nextLong

      public long nextLong(long n)
      Returns a pseudorandom, uniformly distributed value between 0 (inclusive) and the specified value (exclusive).
      Parameters:
      n - the bound on the random number to be returned. Must be positive.
      Returns:
      the next value
      Throws:
      IllegalArgumentException - if n is not positive

    • nextLong

      public long nextLong(long least, long bound)
      Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).
      Parameters:
      least - the least value returned
      bound - the upper bound (exclusive)
      Returns:
      the next value
      Throws:
      IllegalArgumentException - if least greater than or equal to bound

    • nextDouble

      public double nextDouble(double n)
      Returns a pseudorandom, uniformly distributed double value between 0 (inclusive) and the specified value (exclusive).
      Parameters:
      n - the bound on the random number to be returned. Must be positive.
      Returns:
      the next value
      Throws:
      IllegalArgumentException - if n is not positive

    • nextDouble

      public double nextDouble(double least, double bound)
      Returns a pseudorandom, uniformly distributed value between the given least value (inclusive) and bound (exclusive).
      Parameters:
      least - the least value returned
      bound - the upper bound (exclusive)
      Returns:
      the next value
      Throws:
      IllegalArgumentException - if least greater than or equal to bound