Package Summary  Overview Summary

class:ThreadLocalRandom [NONE]

All Implemented Interfaces:
Serializable, RandomGenerator

public final class ThreadLocalRandomextends Random
A random number generator (with period 264) 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 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.

Since:
1.7
See Also:

method:current() [NONE]

  • current

    public static  ThreadLocalRandom current()
    Returns the current thread's ThreadLocalRandom object. Methods of this object should be called only by the current thread, not by other threads.
    Returns:
    the current thread's ThreadLocalRandom
  • method:setSeed(long) [NONE]

    setSeed

    public void setSeed (long seed)
    Throws UnsupportedOperationException. Setting seeds in this generator is not supported.
    Overrides:
    setSeed in class Random
    Parameters:
    seed - the seed value
    Throws:
    UnsupportedOperationException - always

    method:next(int) [NONE]

    next

    protected int next (int bits)
    Generates a pseudorandom number with the indicated number of low-order bits. Because this class has no subclasses, this method cannot be invoked or overridden.
    Overrides:
    next in class Random
    Parameters:
    bits - random bits
    Returns:
    the next pseudorandom value from this random number generator's sequence

    method:nextBoolean() [NONE]

    nextBoolean

    public boolean nextBoolean()
    Returns the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence. The general contract of nextBoolean is that one boolean value is pseudorandomly generated and returned. The values true and false are produced with (approximately) equal probability.
    Specified by:
    nextBoolean in interface RandomGenerator
    Overrides:
    nextBoolean in class Random
    Returns:
    the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence

    method:nextInt() [NONE]

    nextInt

    public int nextInt()
    Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence. The general contract of nextInt is that one int value is pseudorandomly generated and returned. All 232 possible int values are produced with (approximately) equal probability.
    Specified by:
    nextInt in interface RandomGenerator
    Overrides:
    nextInt in class Random
    Returns:
    the next pseudorandom, uniformly distributed int value from this random number generator's sequence

    method:nextInt(int) [NONE]

    nextInt

    public int nextInt (int bound)
    Returns a pseudorandom, uniformly distributed 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.
    Specified by:
    nextInt in interface RandomGenerator
    Overrides:
    nextInt in class Random
    Parameters:
    bound - the upper bound (exclusive). Must be positive.
    Returns:
    the next pseudorandom, uniformly distributed int value between zero (inclusive) and bound (exclusive) from this random number generator's sequence
    Throws:
    IllegalArgumentException - if bound is not positive

    method:nextInt(int,int) [NONE]

    nextInt

    public int nextInt (int origin, int bound)
    Returns a pseudorandomly chosen int value between the specified origin (inclusive) and the specified bound (exclusive).
    Parameters:
    origin - the least value that can be returned
    bound - the upper bound (exclusive) for the returned value
    Returns:
    a pseudorandomly chosen int value between the origin (inclusive) and the bound (exclusive)
    Throws:
    IllegalArgumentException - if origin is greater than or equal to bound

    method:nextLong() [NONE]

    nextLong

    public long nextLong()
    Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence. The general contract of nextLong is that one long value is pseudorandomly generated and returned.
    Specified by:
    nextLong in interface RandomGenerator
    Overrides:
    nextLong in class Random
    Returns:
    the next pseudorandom, uniformly distributed long value from this random number generator's sequence

    method:nextLong(long) [NONE]

    nextLong

    public long nextLong (long bound)
    Returns a pseudorandomly chosen long value between zero (inclusive) and the specified bound (exclusive).
    Parameters:
    bound - the upper bound (exclusive) for the returned value. Must be positive.
    Returns:
    a pseudorandomly chosen long value between zero (inclusive) and the bound (exclusive)
    Throws:
    IllegalArgumentException - if bound is not positive

    method:nextLong(long,long) [NONE]

    nextLong

    public long nextLong (long origin, long bound)
    Returns a pseudorandomly chosen long value between the specified origin (inclusive) and the specified bound (exclusive).
    Parameters:
    origin - the least value that can be returned
    bound - the upper bound (exclusive) for the returned value
    Returns:
    a pseudorandomly chosen long value between the origin (inclusive) and the bound (exclusive)
    Throws:
    IllegalArgumentException - if origin is greater than or equal to bound

    method:nextFloat() [NONE]

    nextFloat

    public float nextFloat()
    Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.

    The general contract of nextFloat is that one float value, chosen (approximately) uniformly from the range 0.0f (inclusive) to 1.0f (exclusive), is pseudorandomly generated and returned. All 224 possible float values of the form m x 2-24, where m is a positive integer less than 224, are produced with (approximately) equal probability.

    Specified by:
    nextFloat in interface RandomGenerator
    Overrides:
    nextFloat in class Random
    Returns:
    the next pseudorandom, uniformly distributed float value between 0.0f and 1.0f from this random number generator's sequence

    method:nextFloat(float) [NONE]

    nextFloat

    public float nextFloat (float bound)
    Returns a pseudorandomly chosen float value between zero (inclusive) and the specified bound (exclusive).
    Implementation Note:
    Parameters:
    bound - the upper bound (exclusive) for the returned value. Must be positive and finite
    Returns:
    a pseudorandomly chosen float value between zero (inclusive) and the bound (exclusive)
    Throws:
    IllegalArgumentException - if bound is not both positive and finite

    method:nextFloat(float,float) [NONE]

    nextFloat

    public float nextFloat (float origin, float bound)
    Returns a pseudorandomly chosen float value between the specified origin (inclusive) and the specified bound (exclusive).
    Implementation Note:
    Parameters:
    origin - the least value that can be returned
    bound - the upper bound (exclusive)
    Returns:
    a pseudorandomly chosen float value between the origin (inclusive) and the bound (exclusive)
    Throws:
    IllegalArgumentException - if origin is not finite, or bound is not finite, or origin is greater than or equal to bound

    method:nextDouble() [NONE]

    nextDouble

    public double nextDouble()
    Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.

    The general contract of nextDouble is that one double value, chosen (approximately) uniformly from the range 0.0d (inclusive) to 1.0d (exclusive), is pseudorandomly generated and returned.

    Specified by:
    nextDouble in interface RandomGenerator
    Overrides:
    nextDouble in class Random
    Returns:
    the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence
    See Also:

    method:nextDouble(double) [NONE]

    nextDouble

    public double nextDouble (double bound)
    Returns a pseudorandomly chosen double value between zero (inclusive) and the specified bound (exclusive).
    Implementation Note:
    Parameters:
    bound - the upper bound (exclusive) for the returned value. Must be positive and finite
    Returns:
    a pseudorandomly chosen double value between zero (inclusive) and the bound (exclusive)
    Throws:
    IllegalArgumentException - if bound is not both positive and finite

    method:nextDouble(double,double) [NONE]

    nextDouble

    public double nextDouble (double origin, double bound)
    Returns a pseudorandomly chosen double value between the specified origin (inclusive) and the specified bound (exclusive).
    Implementation Note:
    Parameters:
    origin - the least value that can be returned
    bound - the upper bound (exclusive) for the returned value
    Returns:
    a pseudorandomly chosen double value between the origin (inclusive) and the bound (exclusive)
    Throws:
    IllegalArgumentException - if origin is not finite, or bound is not finite, or origin is greater than or equal to bound

    method:ints(long) [NONE]

    ints

    public IntStream ints (long streamSize)
    Returns a stream producing the given streamSize number of pseudorandom int values.

    A pseudorandom int value is generated as if it's the result of calling the method Random.nextInt().

    Specified by:
    ints in interface RandomGenerator
    Overrides:
    ints in class Random
    Parameters:
    streamSize - the number of values to generate
    Returns:
    a stream of pseudorandom int values
    Throws:
    IllegalArgumentException - if streamSize is less than zero
    Since:
    1.8

    method:ints() [NONE]

    ints

    public IntStream ints()
    Returns an effectively unlimited stream of pseudorandom int values.

    A pseudorandom int value is generated as if it's the result of calling the method Random.nextInt().

    Specified by:
    ints in interface RandomGenerator
    Overrides:
    ints in class Random
    Implementation Note:
    This method is implemented to be equivalent to ints(Long.MAX_VALUE).
    Returns:
    a stream of pseudorandom int values
    Since:
    1.8

    method:ints(long,int,int) [NONE]

    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).

    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;
       }
     }
    

    Specified by:
    ints in interface RandomGenerator
    Overrides:
    ints in class Random
    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 - if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound
    Since:
    1.8

    method:ints(int,int) [NONE]

    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).

    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;
       }
     }
    

    Specified by:
    ints in interface RandomGenerator
    Overrides:
    ints in class Random
    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 - if randomNumberOrigin is greater than or equal to randomNumberBound
    Since:
    1.8

    method:longs(long) [NONE]

    longs

    public LongStream longs (long streamSize)
    Returns a stream producing the given streamSize number of pseudorandom long values.

    A pseudorandom long value is generated as if it's the result of calling the method Random.nextLong().

    Specified by:
    longs in interface RandomGenerator
    Overrides:
    longs in class Random
    Parameters:
    streamSize - the number of values to generate
    Returns:
    a stream of pseudorandom long values
    Throws:
    IllegalArgumentException - if streamSize is less than zero
    Since:
    1.8

    method:longs() [NONE]

    longs

    public LongStream longs()
    Returns an effectively unlimited stream of pseudorandom long values.

    A pseudorandom long value is generated as if it's the result of calling the method Random.nextLong().

    Specified by:
    longs in interface RandomGenerator
    Overrides:
    longs in class Random
    Implementation Note:
    This method is implemented to be equivalent to longs(Long.MAX_VALUE).
    Returns:
    a stream of pseudorandom long values
    Since:
    1.8

    method:longs(long,long,long) [NONE]

    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).

    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;
     }
    

    Specified by:
    longs in interface RandomGenerator
    Overrides:
    longs in class Random
    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 - if streamSize is less than zero, or randomNumberOrigin is greater than or equal to randomNumberBound
    Since:
    1.8

    method:longs(long,long) [NONE]

    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).

    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;
     }
    

    Specified by:
    longs in interface RandomGenerator
    Overrides:
    longs in class Random
    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 - if randomNumberOrigin is greater than or equal to randomNumberBound
    Since:
    1.8

    method:doubles(long) [NONE]

    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).

    A pseudorandom double value is generated as if it's the result of calling the method Random.nextDouble().

    Specified by:
    doubles in interface RandomGenerator
    Overrides:
    doubles in class Random
    Parameters:
    streamSize - the number of values to generate
    Returns:
    a stream of double values
    Throws:
    IllegalArgumentException - if streamSize is less than zero
    Since:
    1.8

    method:doubles() [NONE]

    doubles

    public DoubleStream doubles()
    Returns an effectively unlimited stream 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().

    Specified by:
    doubles in interface RandomGenerator
    Overrides:
    doubles in class Random
    Implementation Note:
    This method is implemented to be equivalent to doubles(Long.MAX_VALUE).
    Returns:
    a stream of pseudorandom double values
    Since:
    1.8

    method:doubles(long,double,double) [NONE]

    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).
    Specified by:
    doubles in interface RandomGenerator
    Overrides:
    doubles in class Random
    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 - 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
    Since:
    1.8

    method:doubles(double,double) [NONE]

    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).
    Specified by:
    doubles in interface RandomGenerator
    Overrides:
    doubles in class Random
    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 - if randomNumberOrigin is not finite, or randomNumberBound is not finite, or randomNumberOrigin is greater than or equal to randomNumberBound
    Since:
    1.8

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