Exception related code

Question

Hi.
When i try to compile following code it gives compile time errror:
import java.io.*;
class Parent{
public void method1() throws IOException, ArrayIndexOutOfBoundsException{
     System.out.println(" HI this is parent class method");
class Child extends Parent{
public void method1() {
          System.out.println(" HI this is child class method");
public class TestExtendedexception{
     public static void main(String args[]) {
          Parent a = new Child(); // line (1) **********
          a.method1();
Error: unreported exception java.io.IOException; must be caught or declared to be thrown
          a.method1();
However if i Create a refernce of 'Child' class instead of 'Parent' class its not giving compile time error. i.e. Child a = new Child()
Why so?

Answer 1

Compare both method declarations:
While the method method1() (I would suggest another name ;-)) in Class Parent declares that it could throw an IOException or an ArrayIndexOutOfBoundsException while being executed, the method method1() in Class child doesn't.
IOException is a so called checked exception, which has to be thrown to the calling method or handled in a so called try-catch-block.
ArrayIndexOutOfBoundsException on the other hand is a so called RuntimeException, which in most cases isn't handled and throws itself.
As method1() won't ever throw both an IOException or an ArrayIndexOutOfBoundsException (the are no IO- or array-accesses in you method), you can omit the throws declaration...
class Parent{
    public void method1() throws IOException, ArrayIndexOutOfBoundsException{
        System.out.println(" HI this is parent class method");
}For more information on Exceptions, see:
[http://java.sun.com/docs/books/tutorial/essential/exceptions/index.html]