Difference between abstract class and interface

[jagadeesh]

S.No

Abstract Class

method must be declared as abstract.
Abstract methods doesn’t have any definition.
The sub class (extend class) can have the definition for those abstract method.
The Abstract methods can declare with Access modifiers like public, internal, protected.
Abstract class can contain variables and concrete methods.
An abstract class can Inherit only one Abstract class and Multiple inheritance is not possible for Abstract class.


Interface Class
Interface - all the methods by default are abstract methods only.
So one cannot declare variables in interfaces. The sub class (implement class) can have all method definition for those methods.
All methods declared in an interface must be public.
Interfaces cannot contain variables and concrete methods, but we can possible to define the constants.
A class can implement many interfaces and Multiple interface inheritance is possible.