1: // Program by Luis Gallego Cardona. 2: package com.factorialdemo;
3: import javax.swing.*;
4: public class FactorialDemo {
5: public static void main(String[] args) {
6: String input; // hold the input
7: int number; // hold a number
8: // Get the number from the user
9: input = JOptionPane.showInputDialog("Enter a non-negative number");
10: number = Integer.parseInt(input);
11: // Display the users input
12: JOptionPane.showMessageDialog(null, number + "! is " + factorial(number) + ", using recursion"); // This shows the factorial using recursion
13: JOptionPane.showMessageDialog(null, number + "! is " + nonrecursivefactorial(number) + ", not using recursion"); // This shows the factorial NOT using recursion
14: System.exit(0);
15: // NOTE: What is the purpose of System.exit(0)? I know I have to call this whenever I use JOptionPane ... but that's about it.
16: }
17: private static int nonrecursivefactorial(int n) {
18: int x; // this holds the number
19: int fact = 1; // this is a place holder for the result of the factorial
20: /** The for loops takes in a number as x, then assigns the value as n, which is the counter in the for loop.
21: * it then multiplies the number we passed in by 1 (base case), then it keeps multiplying the new number all the way until n is < 1. Thus breaks the loop
22: */
23: for (x = n; x > 1; x--)
24: fact *= x;
25: return fact;
26: }
27: private static int factorial(int n) {
28: if(n == 0)
29: return 1; // this is the base case , because 0! = 1
30: else
31: return n * factorial(n - 1);
32: }
33: }
