Chapter6: Exceptions

Question 1

What should be added at line 2 for the code to compile?
public class Program{
      public static void main(String [] args) { // 2
             new Program().doIt();
             new Program().didIt();
      }
      static void doit()throws java.io.IOException {
             throw new java.io.IOException();
       }
       static void doit()throws ClassNotFoundException {
             throw new SecurityException();
      }
}

Answer 1

public static void main(String [] args) throws java.io.IOException, ClassNotFoundException {

these are checked exceptions meaning that they should be declared or handled in a try/catch block.

Question 2

What will be the output of this program when run with the command java Program 10?
public class Program{
     static Integer I;
      public static void main(String [] args) { 
             String s;
              try{
                   s = I.toString();
            } finally {
                    try{
                            int i = Integer.parseInt(args[0]);
           } catch (NumberFormatException E) {
                    System.out.print("NumberFormat");
           } finally {
                  System.out.print("Fin2");
           }
           System.out.print("Fin1");
           }
     }
}

Answer 2

Fin 2 Fin 1 followed by uncaught exception

A NullPointer is generated as we try to invoke toString method on a null reference. however there is no catch block to catch it. finally executes and prints fin2. fin 1 is then printed and the NullPointer remains uncaught and thus is thrown at the end.