Class Primes


  • public class Primes
    extends java.lang.Object
    This class provides a static table of int sized prime numbers. For small numbers (0-511) it contains all primes. For larger numbers it contains 32 primes each time the number of bits is increased. I.e., there are 32 primes from 512 to 1023, 32 primes from 1024 to 2048, etc., the primes thus becoming less dense with size. Within the interval formed by using one more bit (say, v0 to v1), the 32 primes are formed by searching for the first prime greater than or equal to v0 + n*(v1-v0)/32, n belonging to {0,1,2, ..., 31}. This creates a reasonable distribution.
    Since:
    1.0
    Version:
    1.2 21-08-2003 20:21
    • Field Summary

      Fields 
      Modifier and Type Field Description
      private static int[] primes
      Prime numbers in ascending order.
    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private Primes()
      Prevents instantiation.
    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static int nextPrime​(int n)
      Returns from a static prime table the least prime that is greater than or equal to a specified value.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • primes

        private static final int[] primes
        Prime numbers in ascending order.
    • Constructor Detail

      • Primes

        private Primes()
        Prevents instantiation.
    • Method Detail

      • nextPrime

        public static int nextPrime​(int n)
        Returns from a static prime table the least prime that is greater than or equal to a specified value. On average, the returned prime will about 1/64 of 2(r+1) - 2r greater than n, where r is the order of n (the number of bits required for representing it).
        Returns:
        the least prime in the table that is greater than or equal to the specified value.