you never get a chance to choose a method from abstract 
class,because  if  you are writing a abstract class you 
have to provide implementation to all the methods in 
subclass otherwise you should declare that subclass as 
Abstractclass.

Better to choose Abstract class. Because it contains not 
only the abstract methods but also implemented methods but 
in interfaces only unimplemented methods will be there and 
all final variables will be there.

i preferred to choose interface bcoz 
 if i implement interface still i have a chance to extend 
 another class

Interface is preferable to Abstract class as when ever in 
instance is created for subclasses of this,constructors 
will be called hirarchially consuming some time for each 
constructor call..