Interface in Java

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.

Why use Java interface?

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.

Java 8 Interface Improvement

Since Java 8, interface can have default and static methods which is discussed late

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

Java Interface Example

In this example, Printable interface has only one method, its implementation is provided in the A class.

1. interface printable{  
2. void print();  
3. }  
4. class A6 implements printable{  
5. public void print(){System.out.println("Hello");}  
6.   
7. public static void main(String args[]){  
8. A6 obj = new A6();  
9. obj.print();  
10.  }  
11. }  

Output: Hello