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Need Help

Anis Malik

Joined: Jan 29, 2007
Posts: 1
Noob here.. Hello everyone...

I am using the K&B SCJP study guide for the exam and I am having difficulty understanding one of the Self-Test questions. The book recommended this forum for help. So...

It's question #13 from Chapter 2:
It goes something like this:
class Dog {}
class Beagle extends Dog{}
Beagle b1 = new Beagle();
Dog d2 = b1;

some options are given and one of them is: Beagle b4 = d2. I tried it and it compiles fine but it's not included as one of the possible answers.

Remko Strating
Ranch Hand

Joined: Dec 28, 2006
Posts: 893
I think you mean option C.

This will not compile and I have tried this.

The reason is that you need to do an explicit cast if you want to cast from Dog to Beagle, because Beagle is a subclass of Dog. The following line will compile

Beagle b4 = (Beagle)dog2;

If Beagle was the superclass of Dog then option C would compile.

Remko (My website)
SCJP 1.5, SCWCD 1.4, SCDJWS 1.4, SCBCD 1.5, ITIL(Manager), Prince2(Practitioner), Reading/ gaining experience for SCEA,
I agree. Here's the link:
subject: Need Help
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