1. Interface

2. Interface
In Java, an interface is a reference type, similar to a class
Can contain constants and method signatures
There are no method bodies
Cannot be instantiated - they can only be implemented by classes or extended by other interfaces
Variables and the methods declared in interfaces are public by default
An interface can extend another interface
A class can implement multiple interfaces

3. Interface
A class that contains only abstract methods and/or named constants
How Java implements multiple inheritance
To be able to handle a variety of events, Java allows a class to implement more than one interface

4. Interface Why Interface?
To reveal an object's programming interface (functionality of the object) without revealing its implementation
To have unrelated classes Implement similar methods (behaviors)
To model multiple inheritance
interface Int1 {
... }
interface Int2 {
class Test implements Int1,
Int2 {
class Test1{
... }
interface Int3 {
class Test extends Test1
implements Int3{

5. Interfaces and Abstract classes can not be instantiated
Example of an interface declaration:
public interface Interface1 {
public void set(int i);
public int get(); }
Interface1 i1 = new Interface1 ();
Interfaces and Abstract classes can not be instantiated

6. Interface Example interface Shape { private double pi=3.14;
public void getArea(int a); }
class Circle implements Shape {
public void getArea(int r) {
double area=pi*r*r;
System.out.println("Area is " + area);
public class interfaceDemo {
public static void main (string args[]) {
Circle ci=new Circle();
c1.getArea(3);

7. Interface Example interface shape{ void area(); }
}     
class A6 implements shape{  
public void area(){System.out.println(“This is area");}  
public static void main(String args[]){  
A6 obj = new A6();  
Obj.area();  
  }