Talk:Java Training Course/JT04

Complete program:

public class DupInt {
    public static void main(String[] args) {
        int st0 = Integer.parseInt(args[0]); // the 1st argument on the commandline
        int st1 = Integer.parseInt(args[1]); // the 2nd ...
        int st2 = st0 + st1;
        st2 = st2 + st2 + st2 + st2;
        System.out.println(st2);
    } // main
} // DupInt

Output with different arguments:

georg@nunki:~/work/project/bekasi/JTC$ java DupInt 2 4
 24
georg@nunki:~/work/project/bekasi/JTC$ java DupInt 2 -4
-8
georg@nunki:~/work/project/bekasi/JTC$ java DupInt 0 -1
-4
georg@nunki:~/work/project/bekasi/JTC$ java DupInt
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
	at DupInt.main(DupInt.java:3)

parseInt(String) is a static method in the Java class java.lang.Integer which attempts to convert a String and return an int. It fails if the String does not have the proper syntax of an int. We will later learn how to prevent this hard failure of the program by using a try { ... } catch block around sensible operations.