Answer Posted / lakshmi

Interface has no implementation, but they have to be
implemented.
Abstract class’s methods can have implementations and they
have to be extended.
Interfaces can only have method declaration (implicitly
public and abstract) and fields (implicitly public static)
Abstract class’s methods can’t have implementation only
when declared abstract.
Interface can inherit more than one interfaces
Abstract class can implement more than one interfaces, but
can inherit only one class
Abstract class must override all abstract method and may
override virtual methods
Interface can be used when the implementation is changing
Abstract class can be used to provide some default behavior
for a base class.
Interface makes implementation interchangeable
Interface increase security by hiding the implementation
Abstract class can be used when implementing framework
Abstract classes are an excellent way to create planned
inheritance hierarchies and also to use as non-leaf classes
in class hierarchies.

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