What is the difference between an interface and an abstract class in Java?

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What is the difference between an interface and abstract class?

What is the difference between an interface and an abstract class in Java? Why would I want to use one over the other?

http://stackoverflow.com/questions/1913098/what-is-the-difference-between-an-interface-and-abstract-class — lockstock, Apr 17 '12 at 05:36
Java is not an acronym nor is it stylized in all capital letters, so not quite sure why you've written "JAVA". — Corbin, Apr 17 '12 at 05:37
Why people give me bad points when im asking a question and be polite with everyone ? — darkuzul, Apr 17 '12 at 05:46
@darkuzul: you could have searched for similar questions already asked on this forum instead of posting a new question. — Shashank Kadne, Apr 17 '12 at 05:48
I'm sorry im new i explained that this is my first post in my post but somebody deleted everything i wrote i dont understand why. — darkuzul, Apr 17 '12 at 05:56

score 3 · Answer 1 · answered Apr 17 '12 at 05:38

An abstract class can contain implementations, but it is a class and you can only extend one class.

An interface just contains declarations no implementations and you can implement as many interfaces as you want.

If you don't need to implement any methods go with interfaces.

If you have to implement a method go with an abstract class, but consider having it implement an interface. This will allow you to use alternative implementations in cases where you can't use the abstract class for example due to the impossibility of multiple inheritance.

That's a nice answer i think i understand a bit now thank you — darkuzul, Apr 17 '12 at 05:39

score 0 · Answer 2 · answered Apr 17 '12 at 05:36

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Well its a very broad question, there are a lot of difference between them, it is impossible to discuss all of them here, you can google it to get good answers, but

Broadly speaking abstract class is a partially implemented partially unimplemented structure but interface is a fully unimplemented structure

answered Apr 17 '12 at 05:36

Chandra Sekhar

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Thank you for that but when do you choose to use an abstract class upper an interface ? – darkuzul Apr 17 '12 at 05:37
I'm trying to give you points but it says I have to have 15 how do I give you ? Sorry – darkuzul Apr 17 '12 at 05:38
Wait for a couple of upvotes for your question(s) and answers and you will get the option to upvote. – Jens Schauder Apr 17 '12 at 05:38

score 0 · Answer 3 · answered Apr 17 '12 at 06:07

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Here is my explanation with some real life example which has been written 2 years ago -

http://karthikjcecs.wordpress.com/2009/01/14/java-interfaces-versus-abstract-class/

Hope it helps you understand better.

answered Apr 17 '12 at 06:07

Karthik Ananth

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What is the difference between an interface and an abstract class in Java?

3 Answers3