Programming Forums - View Single Post - Query regarding extending Exception classes

arj · Apr 25th, 2008, 4:08 PM

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:

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public class MyException extends Exception {
    public MyException(String message) {
        super(message); 
    }
}

I then added the line:

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 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:

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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.

Apr 25th, 2008, 4:08 PM	#1
arj Newbie Join Date: Apr 2008 Posts: 1 Rep Power: 0	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: (Toggle Plain Text) public class MyException extends Exception { public MyException(String message) { super(message); } } public class MyException extends Exception { public MyException(String message) { super(message); } } I then added the line: (Toggle Plain Text) public MyClass() { ... else throw new MyException("message"); ... } 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: (Toggle Plain Text) public class MyException extends IllegalArgumentException { 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.