Types of methods

       1.Concrete method

1. A method having the signature and body contents and can be used and  overridden in child class.By default all methods are concrete.

      2.Abstract methods

1. A method having the signature but no body contents
2. Such methods can be declared at two places

                                                              i.      Abstract class

                                                            ii.      Interface

3. If declared inside an abstract class then use abstract keyword with the methods.
4. If declared inside an interface, no keyword is required, since all methods inside an interface are public and abstract by default
5. Such methods are always overridden by child class

       2.Final methods

1. A method that can never be overridden is called as final method

b.      Use final keyword to declare such methods

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Types of classes

If we can create an object(instance)  of a class then that class is called instantiated.

Inherited  mean we  get all the functionality (all of attributes, properties, and methods) of that class which is inherited to new class.

In java there are three types of classes----

1.concrete class:A class that can be instantiated and also can be inherited is called as concrete class.

All class are by default concrete.

2.Abstract class: A class that can never be instantiated and  can be inherited is called as abstract  class.

Such  classes must have abstract  keyword  associated with them.

3.Final class: A class that can be instantiated and can never be inherited is called as final class.

Use final keyword to make such a class.

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