[JAVA API] java.util.Random

java.util

Class Random

• java.lang.Object
• • java.util.Random

• All Implemented Interfaces:

  Serializable

  Direct Known Subclasses:

  SecureRandom, ThreadLocalRandom

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  public class Random
  extends Object
  implements Serializable

  An instance of this class is used to generate a stream of pseudorandom numbers. The class uses a 48-bit seed, which is modified using a linear congruential formula. (See Donald Knuth, The Art of Computer Programming, Volume 2, Section 3.2.1.)

  If two instances of Random are created with the same seed, and the same sequence of method calls is made for each, they will generate and return identical sequences of numbers. In order to guarantee this property, particular algorithms are specified for the class Random. Java implementations must use all the algorithms shown here for the class Random, for the sake of absolute portability of Java code. However, subclasses of class Random are permitted to use other algorithms, so long as they adhere to the general contracts for all the methods.

  The algorithms implemented by class Random use a protected utility method that on each invocation can supply up to 32 pseudorandomly generated bits.

  Many applications will find the method Math.random() simpler to use.

  Instances of java.util.Random are threadsafe. However, the concurrent use of the same java.util.Random instance across threads may encounter contention and consequent poor performance. Consider instead using ThreadLocalRandom in multithreaded designs.

  Instances of java.util.Random are not cryptographically secure. Consider instead using SecureRandom to get a cryptographically secure pseudo-random number generator for use by security-sensitive applications.

  Since:

  1.0

  See Also:

  Serialized Form

• • Constructor Summary

    Constructors 

    Constructor and Description
    Random() Creates a new random number generator.
    Random(long seed) Creates a new random number generator using a single long seed.

  • Method Summary

    Methods 

    Modifier and Type	Method and Description
    protected int	next(int bits) Generates the next pseudorandom number.
    boolean	nextBoolean() Returns the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence.
    void	nextBytes(byte[] bytes) Generates random bytes and places them into a user-supplied byte array.
    double	nextDouble() Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.
    float	nextFloat() Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.
    double	nextGaussian() Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence.
    int	nextInt() Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence.
    int	nextInt(int n) Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
    long	nextLong() Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence.
    void	setSeed(long seed) Sets the seed of this random number generator using a single long seed.

    • Methods inherited from class java.lang.Object

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