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JQ+ question on interfaces

natarajan meghanathan
Ranch Hand

Joined: Feb 01, 2001
Posts: 130
Which of the following with interfaces are true: [check 2 answers]
1) Interfaces are abstract by default.
2) An Interface can have static methods.
3) Interfaces cannot be final.
4) Fields of an interface can be declared transient, volatile but not synchronized.
5) All methods in an interface are abstract, although u need not declare them to be so.
I went for 1,3
But the answer given is 1,5.
There is a mild catch i thought which made me to go for 3 rather than 5. They say u need not declare the methods as abstract in option 5. That means i thought, it is legal to declare them to be abstract (which is not so!!). So i went for option 3 which is also perfectly true. (Interfaces cannot be declared final!!).
Any help.

Sun Certified Programmer for Java 2 Platform
Paul Anilprem
Enthuware Software Support
Ranch Hand

Joined: Sep 23, 2000
Posts: 3636
Your are right. Interfaces cannot be final. This was a bug in the question. I remember fixing it a couple days ago.
But it is legal to declare a method as abstract in an interface. It is not recommended to do so, though.
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