[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

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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 

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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

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1 2	public interface Serializable{ }