ABSTRACT METHOD AND CLASSES

     In Java, it is possible to define a method that must always be redefined in a subclass, thus making overriding compulsory. This is done using the keyword abstract in the method definition.

Ex: abstract class A {

          …….

          abstractvoid show();

…….

      } 

    When a class contains one or more abstract methods, it should also be declared abstarct.

     While using abstract classes, the following conditions must be defined:

o   We can’t use abstract classes to instantiate objects directly:

Ex:A a=new A(); is illegal because a is an abstract class.

o   Abstarct method of an abstract class must be defined in its subclass.

o   We can’t declare abstract constructors or abstract static methods.