Package org.apache.commons.numbers.combinatorics

Class FactorialDouble

  • public class FactorialDouble
extends java.lang.Object
    Class for computing the natural logarithm of the factorial of a number. It allows to allocate a cache of precomputed values.

    • Method Summary

      Modifier and Type Method Description
      static FactorialDouble create()
      Creates an instance with no precomputed values.
      double value​(int n)
      Computes the factorial of n.
      FactorialDouble withCache​(int cacheSize)
      Creates an instance with the specified cache size.

      • Methods inherited from class java.lang.Object

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

    • Method Detail

      • create

        public static FactorialDouble create()
        Creates an instance with no precomputed values.
        Returns:
        instance with no precomputed values

      • withCache

        public FactorialDouble withCache​(int cacheSize)
        Creates an instance with the specified cache size.
        Parameters:
        cacheSize - Number of precomputed values of the function.
        Returns:
        a new instance where cacheSize values have been precomputed.
        Throws:
        java.lang.IllegalArgumentException - if cacheSize < 0.

      • value

        public double value​(int n)
        Computes the factorial of n. The result should be small enough to fit into a double: The largest n for which n! does not exceed Double.MAX_VALUE is 170. Double.POSITIVE_INFINITY is returned for n > 170.
        Parameters:
        n - Argument.
        Returns:
        n!
        Throws:
        java.lang.IllegalArgumentException - if n < 0.