Abstract Class:
  • To define a class as Abstract, the keyword abstract is to be used. 
  • In abstract class at least one method must be abstract.
  • we can create object of abstract class.
  • abstract classes may not be instantiated.
  • The child classes which inherits the property of abstract base class, must define all the methods declared as abstract.
  • Any class that contains at least one abstract method must also be abstract.
  • If the abstract method is defined as protected, the function implementation must be defined as either protected or public, but not private.
  • Abstract class can contain variables and concrete methods.
  • A class can Inherit only one Abstract class and Multiple inheritance is not possible for Abstract class.

  • In interface all the method must be abstract.
  • All methods declared in an interface must be public.
  • Interfaces cannot contain variables and concrete methods except constants.
  • A class can implement many interfaces and Multiple interface inheritance is possible.
  • To extend from an Interface, keyword implements is used.