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what is an interface?

Posted By :Narayanan     Posted Date :November 22, 2011    Points :40   Category :OOPS 
It is not a class.
it is only definition of the methods without the body.

You can also find related Interview Question to what is an interface?  below: 

What is the difference between interface and abstract class ?

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What is difference between abstract class and an interface?

An Abstract class is a class with some common/certain implementations and defines abstraction for other services which are implemented in its concrete sub classes, whereas interface only have method declaration with zero implementations. An abstract class and Interface both have method only but not have body of method. The difference between Abstract class and An Interface is that if u call Abstract class then u have to call all method of that particular Abstract class but if u call an Interface then it is not necessary that u call all method of that particular interface. An abstract class is a special kind of class that cannot be instantiated. So the question is why we need a class that cannot be instantiated? An abstract class is only to be sub-classed (inherited from). In other words, it only allows other classes to inherit from it but cannot be instantiated. The advantage is that it enforces certain hierarchies for all the subclasses. In simple words, it is a kind of contract that forces all the subclasses to carry on the same hierarchies or standards.

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Can you describe IUKNOWN interface in short ?

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