[Java] Interface

Interface

- interface is a blueprint of a class

- It has static constants and abstract methods only

- It is used to achieve fully abstraction and multiple inheritance in java

1. Why use it

- It is used to achieve fully abstraction

- By interface, we can support the functionality of multiple inheritance

- It can be used to achieve loose coupling

- The java compiler adds public and abstract keywords before the interface method and public, static and final keywords before data members

2. Example

interface printable{ void print(); } class A implements printable{ public void print(){ System.out.println("Hello"); } } public class Test{ public static void main(String[]args){ A obj = new A(); obj.print(); } }

3. Multiple inheritance 

interface printable{ void print(); } interface showable{ void show(); } class A implements printable, showable{ public void print(){ System.out.println("Hello"); } public void show(){ System.out.println("Show"); } } public class Test{ public static void main(String[]args){ A obj = new A(); obj.print(); obj.show(); } }  

1) Is it possible by interface, why?

- There is no ambiguity as implementation is provided by the implementation class

4. What is marker or tagged interface?

- An interface that have no member is known as marker or tagged interface

- Serializable, Cloneable, Remote....

- They are used to provide some essential information to the JVM so that JVM may perform some useful operation

public interface Serializable{ }