We could have included this code in our main method, but the algorithm is much easier to understand by breaking the code into smaller, more manageable pieces. It's also easier to test and debug. We can write a simple program that lets us test the factorial method before we worry ourselves with the much harder problem of accepting and validating user input. Here's the test program:

class FactorialTest { public static void main(String args[]) { int n; int i; long result; for (i=1; i <=10; i++) { result = factorial(i); System.out.println(result); } } // main ends here static long factorial (int n) { int i; long result=1; for (i=1; i <= n; i++) { result *= i; } return result; } // factorial ends here }