Interface

• An interface in java is a blueprint of a class. It has static constants and abstract methods.
• The interface in java is a mechanism to achieve abstraction. There can be only abstract methods in the java interface not method body. It is used to achieve abstraction and multiple inheritance in Java.
• Java Interface also represents IS-A relationship.
• It cannot be instantiated just like abstract class.
• There are mainly three reasons to use interface. They are given below.

• It is used to achieve abstraction.
• By interface, we can support the functionality of multiple inheritance.
• It can be used to achieve loose coupling.

Class to Class derive–extends
Interface to Class derive–implement
Interface to Interface derive–extends