java.util.concurrent

Class ThreadLocalRandom

Table des matières
  • All Implemented Interfaces:
    Serializable

    public 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 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

      Methods 
      Modifier and Type Method and Description
      static ThreadLocalRandom current()
      Returns the current thread's ThreadLocalRandom.
      protected int next(int bits)
      Generates the next pseudorandom number.
      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.

        

    • Method Detail

      • 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
        Parameters:
        seed - the initial seed
        Throws:
        UnsupportedOperationException - always

      • next

        protected int next(int bits)
        Description copied from class: Random
        Generates the next pseudorandom number. Subclasses should override this, as this is used by all other methods.

        The general contract of next is that it returns an int value and if the argument bits is between 1 and 32 (inclusive), then that many low-order bits of the returned value will be (approximately) independently chosen bit values, each of which is (approximately) equally likely to be 0 or 1. The method next is implemented by class Random by atomically updating the seed to 

        (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)
        and returning 
        (int)(seed >>> (48 - bits)).
        This is a linear congruential pseudorandom number generator, as defined by D. H. Lehmer and described by Donald E. Knuth in The Art of Computer Programming, Volume 3: Seminumerical Algorithms, section 3.2.1.
        Overrides:
        next in class Random
        Parameters:
        bits - random bits
        Returns:
        the next pseudorandom value from this random number generator's sequence

      • 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

Traduction non disponible

Les API Java ne sont pas encore traduites en français sur l'infobrol. Seule la version anglaise est disponible pour l'instant.

Version en cache

22/12/2024 15:25:56 Cette version de la page est en cache (à la date du 22/12/2024 15:25:56) afin d'accélérer le traitement. Vous pouvez activer le mode utilisateur dans le menu en haut pour afficher la dernère version de la page.

Document créé le 11/06/2005, dernière modification le 04/03/2020
Source du document imprimé : https://www.gaudry.be/java-api-rf-java/util/concurrent/ThreadLocalRandom.html

L'infobrol est un site personnel dont le contenu n'engage que moi. Le texte est mis à disposition sous licence CreativeCommons(BY-NC-SA). Plus d'info sur les conditions d'utilisation et sur l'auteur.

Références

  1. Consulter le document html Langue du document :fr Manuel PHP : https://docs.oracle.com

Ces références et liens indiquent des documents consultés lors de la rédaction de cette page, ou qui peuvent apporter un complément d'information, mais les auteurs de ces sources ne peuvent être tenus responsables du contenu de cette page.
L'auteur de ce site est seul responsable de la manière dont sont présentés ici les différents concepts, et des libertés qui sont prises avec les ouvrages de référence. N'oubliez pas que vous devez croiser les informations de sources multiples afin de diminuer les risques d'erreurs.

Table des matières Haut