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Q on abstract classes

Kedar Dravid
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Joined: May 28, 2004
Posts: 333
Recently, at an interview, I was asked the following question:
"Of what use would be an abstract class which has only one non-abstract method?"

I couldn't quite figure out the answer to this one. Any pointers in this direction would be welcome.
Barry Gaunt
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Joined: Aug 03, 2002
Posts: 7729
Here's my guess: Suppose the class in question was a class named A.
Suppose A extended another abstract class S, or implemented an interface I, but A did not provide an implementation for any methods in the superclass S or interface I, then the class A must be declared abstract. The fact that it provides a single non-abstract method is irrelevant, I think. On the other hand, a class A with no behaviour (methods) at all would be rather pointless.

Ask a Meaningful Question and HowToAskQuestionsOnJavaRanch
Getting someone to think and try something out is much more useful than just telling them the answer.
It is sorta covered in the JavaRanch Style Guide.
subject: Q on abstract classes