Package co.paralleluniverse.strands

Class StrandLocalRandom

  • All Implemented Interfaces:
    java.io.Serializable
    public class StrandLocalRandom
extends java.util.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 accidently share a ThreadLocalRandom across multiple threads.

    This class also provides additional commonly used bounded random generation methods.

    Since:
    1.7
    See Also:
    Serialized Form

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static StrandLocalRandom 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.

      • Methods inherited from class java.util.Random

        doubles, doubles, doubles, doubles, 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

    • Method Detail

      • current

        public static StrandLocalRandom 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 java.util.Random
        Throws:
        java.lang.UnsupportedOperationException - always

      • next

        protected int next​(int bits)
        Overrides:
        next in class java.util.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:
        java.lang.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:
        java.lang.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:
        java.lang.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:
        java.lang.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:
        java.lang.IllegalArgumentException - if least greater than or equal to bound