Interface in Java

 

Interface:

A : Abstract class

B : Abstract class

If we want to declare the definition of method of A and B in C (Another class)

class C extends A, B.   // Multiple Inheritance , Java does not support Inheritance

In order to support Multiple Inheritence, Interface is used 

In abstract class, method can be declared and defined also 

In Interface, method can be only declared

If A and B are interface then

 C can be implemented like 

class C implements A, B

Interface A

{

public void show();

}

Class B implements A

{

public void show()

{

System.out.println(“Hello”);

}

public void display()

{

System.out.println(“Hi”);

}

}

B obj = new B();

Then obj.show() and obj.diplay() can be called, So, object can use show and display method

But, If we wish to restrict user to use only show

Object of interface can not be created but it can be refrenced.  

A obj = new B(); // obj is reference of A and giving memory of B 

obj.show(); // show belongs to A 

obj.display(); // through error as display does not belongs to A, it belongs to B

This is the main reason why interface is largely used