public class Recursion {
    
    public static void main(String[] args) {
        if(args.length > 0) {
            displayFactorial(Integer.parseInt(args[0]));
            return; 
        }

        System.out.println("Usage: java Recursion <number>");
    }

    public static void displayFactorial(int n) {
        System.out.println(n + "! = " + factorial(n, 0));
    }

    private static int factorial(int n, int count) {
        count++;
        System.out.println("n = " + n + " | count = " + count);

        if(n == 0) {
            //Thread.dumpStack();
            return 1; 
        }

        return n * factorial(n - 1, count);
    }
}