Programming Forums - Query regarding extending Exception classes

Hi there

I'm doing a small project at home (and possibly thinking of proposing something similar for my final year project at uni) and I found a slight ... thing ... which I'm not too clear about.

I was writing a class (call it MyClass) and found the need to write an Exception class, something I have done many times in the past. The Exception class looked like this:

public class MyException extends Exception {

    public MyException(String message) {

        super(message); 

    }

}

I then added the line:

 public MyClass() {

        ...

    else throw new MyException("message");

        ...

}

to the constructor of MyClass. The compiler obviously complained saying that I need a 'throws' clause on the method header which I added (public MyClass() throws MyException), which I added on.

Then I decided to play around a little, so I changed the class declaration of MyException to:

public class MyException extends IllegalArgumentException {

(The reason was that in the particular scenario I was trying to capture, MyException was an exception related to illegal paramaters being passed). After doing this I noticed that the compiler no longer asked for a 'throws' clause on the method header which was throwing MyException. :-/ :| I was a bit confused about this, and was wondering if anyone could explain the reasons why this happens?

Thanks,
arj.