Hi Kalyani,
Well the abstract cla and the interface , these are 2 diff. entities. and not the same.
1. u can implement some methods in abstract class and u can keep some of them as abstract so that the derived class implements it. In the interface all methods are by default abstarct. u can not provide implementation to any generalised method also. the implementing class HAS TO implement those methods.
2. u can have private, protected instance member variables in abstract class. In the interface all variables are by default public static and final. u can't have private or protected in interface.
3. The interface is
java's way to provide multiple inheritance functionality in OOPs. u can not extend 2 abstract classes at a time in java, however, u can very well implement 2 interfaces.
Hope this helps. :-)
Rashmi