About Question com.enthuware.ets.scjp.v6.2.649 :

[chang_surrey]

May I ask why option 5 is wrong?

"Overriding method may choose not to throw any exception."

I chose option 3 because class A obviously doesn't compile, but I'm curious what makes option 5 a wrong answer.

Since the original method only throws an unchecked NPE, I assume its overriding version is free to throw nothing at all? Thanks!

[admin]

It is true that the overriding method may choose not to throw any exception. But that implies that the given code is fine, which it is not. That is why that option is incorrect.
Since you have to select one option, you need to select the best option.

[makemoneyy]

This question is ambigious and should be avoided. Specially when multiple answer can be selected. I see the option 1, 3, and 5 are valid.

[msalam4]

Can you please explain why option 1 is wrong? Thanks.

[admin]

Please read the discussion above.

[fortesp]

I am confused...

Overriding method cannot throw IOException

The following snippet compiles:

Code: Select all

class A {
    byte getStatusCode(Object obj) throws NullPointerException {
        if (obj != null) return 127;
        else return -1;
    }
}

class B extends A {
    byte getStatusCode(Object obj) throws IOException {
        if (obj != null) return 127; // changed from 128 to 127.. for the example
        else throw new IOException();
    }
}

And then...

Since IOException is a checked exception and is not a subclass of NullPointerException, the overriding method cannot throw this exception.

[admin]

The following snippet compiles:
....

Are you sure?

[fortesp]

You are right! My IDE did not show any warning...

Its funny though. If i leave just the throws clause it compiles, but if i throw the exception it does not compile. So in terms of method override, i can use throws but not throw an actual exception.