In mathematics, the factorial of a natural number n is the product of all positive integers less than or equal to n. This is written as n! and pronounced "n factorial", or colloquially "n shriek" or "n bang". The notation n! was introduced by Christian Kramp in 1808.

This tip shows how to implement factorial function in Java.

 public class Factorial
{
    // Evaluate n!
    public static long factorial( int n )
    {
        if( n <= 1 )     // base case
            return 1;
        else
            return n * factorial( n - 1 );
    }

    // Simple test program
    public static void main( String [ ] args )
    {
        for( int i = 1; i <= 10; i++ )
            System.out.println( factorial( i ) );
    }
}