/* Basic Algorithms, Fall98, Fall99 (Yap)
 * file: Factorial1.java
 *
 * Variant of Factorial.java to illustrate
 *
 *    --  a subtle issue of initialization of variables
 *    --  the e.getMessage() method in exceptions
 *
 */

class Factorial1 {

  static int computeFactorial(int k) {
    if (k<0) return -1;
    else if (k == 0 || k == 1) return 1;
    else return k * computeFactorial(k-1);
  }

  public static void main(String[] args) {
    int n=0;		// if you do not initialize n here,
			// the compiler will complain.  Why?

  try{ n = Integer.parseInt(args[0]);
			// Reason: n is supposed to be initialized in
			// this try block which may not happen!
  } catch (Exception e){
	System.out.println(e.getMessage());
			// As it turns out, e.getMessage() returns 0
	System.out.println("Error: argument must be integer");
	return ;
  }

    for (int i = 0; i <= n; i++)
	System.out.println
	  (i + " factorial is " + computeFactorial(i));
  }
}