Inheritance :
  • It is a practice in Java programming for class to use or reuse the members those belong to another class.
  • The class that inherits rights to use the members belonging to the other class, is known as derived or child or subclass.
  • And the class that servers the subclass, is called super class, base-class, parent-class.
  • A parent-child relation exists between base-class and derived-class.
  • A key word that allows a derived class to inherit a base class is "extends".
  • In Java , unlike C#, one class can inherit only one parent class.
  • Java does not allow to inherit an interface, but can create an instance of an interface.
  • a class can extend one other class and implement many Java interfaces
  • The sub class may have its own members.


Also See: Link
All primitive data must be define and instantiated

Interface can't implement another interface

One class can't implement another class, but an abstract class can create an abstract of the method that can be overridden in an extended class.

In the above illustration, since the interface Note_1 is extended by another interface Note, when the Note_1 interface is extended in an abstract class, this abstract class will inherit the member functions and variables of Note_1 interface along with Note interface.
However, the class that will inherit an abstract class all the members should be implemented

Now we can compile the class

It is also allowed