Interface in Java

Dear readers,

We already know that java does not support multiple Inheritance,But we can achieve multiple inheritance using the concept called INTERFACE.

INTERFACE?

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An interface in Java is similar to a class, but the body of an interface can include only abstract methods and final fields (constants). A class implements an interface by providing code for each method declared by the interface.

SYNTAX:

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access specifier interface interfacename

{

abstract method();

}

Ex:

public interface Playable

{

    void play();

}

ll the methods in an interface are assumed public and abstract. To implement an interface, a class must do two things:

·         It must specify an implements clause on its class declaration.

·         It must provide an implementation for every method declared by the interface.

Here’s a class that implements the Playable interface:

public class learnjava implements Playable

{

    // additional fields and methods go here

    public void play()

    {

       // code that plays the game goes here

    }

    // additional fields and methods go here

}

Here, the declaration for the learnjava  class specifies implements Playable. Then the body of the class includes an implementation of the play method.

A class can implement more than one interface:

Syntax for Implementing more than on Interface:

public class classname implements interfacename1,interfacename2      

{

static final int code="1001";          //final variable declaration

   abstract methods();

}

EX:

public class HeartsGame implements Playable, CardGame       

{

    // must implement methods of the Playable

    // and CardGame interfaces

}

NOTE:

1) An Interface must contain abstract function.

2)It must have only final variables

3)All the abstract method of a interface should be implemented in a class.