gnu.trove.impl

Class PrimeFinder


  • public final class PrimeFinder
extends Object
    Used to keep hash table capacities prime numbers. Not of interest for users; only for implementors of hashtables.

    Choosing prime numbers as hash table capacities is a good idea to keep them working fast, particularly under hash table expansions.

    However, JDK 1.2, JGL 3.1 and many other toolkits do nothing to keep capacities prime. This class provides efficient means to choose prime capacities.

    Choosing a prime is O(log 300) (binary search in a list of 300 ints). Memory requirements: 1 KB static memory.

    • Field Summary

      Fields

      Modifier and Type Field and Description
      static int largestPrime
      The largest prime this class can generate; currently equal to Integer.MAX_VALUE.

    • Constructor Summary

      Constructors

      Constructor and Description
      PrimeFinder()
       

    • Field Detail

      • largestPrime

        public static final int largestPrime
        The largest prime this class can generate; currently equal to Integer.MAX_VALUE.
        See Also:
        Constant Field Values

    • Constructor Detail

      • PrimeFinder

        public PrimeFinder()

    • Method Detail

      • nextPrime

        public static final int nextPrime(int desiredCapacity)
        Returns a prime number which is >= desiredCapacity and very close to desiredCapacity (within 11% if desiredCapacity >= 1000).
        Parameters:
        desiredCapacity - the capacity desired by the user.
        Returns:
        the capacity which should be used for a hashtable.