Can someone give me an idea of when the abstract class and interfaces has to be used? [duplicate]

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When to use an interface instead of an abstract class and vice versa?

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Can someone give me an idea of when the abstract class and interfaces has to be used?

IF possible supporting with a real time example?

Thanks in Advance.

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An interface is a complete abstraction of some role. You use an interface when you want to ensure certain related behaviours in a type.

An abstract class is more of a default behaviour / infrastructure provider for a collection of classes with some commonality. You use an abstract class when you have some idea of how a collection of classes should behave but would like to refine and augment the behaviour specifically in the individual classes that are extending the abstract class.

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abstract classes are designed with implementation gaps for sub-class to fill in.

interfaces are syntactically similar to classes but they lack instance variables & methods.

abstract classes can also have both abstract methods & non-abstract methods. where as in interface methods are abstract only, & variables are implicitly static&final.

see the links for more detail

http://codeofdoom.com/wordpress/2009/02/12/learn-this-when-to-use-an-abstract-class-and-an-interface/

http://www.sap-img.com/java/when-we-go-for-abstract-and-interface.htm