- blueprint of class

- used to achieve abstraction & multiple inheritance

Syntax:

interface interface_name{

methods; // abstract,public

fields; // static,final,public

}

- only have abstract & public methods(by default)

- fields are static,final & public(by default)

- represents IS-A relationship

- cannot instantiate

- achieve loose coupling

relationships

class----->class - extends

class----->interface - implements

interface----->interface - extends

Difference

Abstract class Interface

1. abstract/non-abstract 1. only abstract methods

2. achieve partial abstraction 2. 100% abstraction

3. abstract class should extended 3. interface should be implemented using

using extends keyword implement keyword

4.fields - non-final 4. final

*********Marker Interface***************

- empty interface(no fields or methods)

- interface that does not contain any methods,fields

- tag interface

- it delivers additional info to the JVM about an object @run time

- inform the compiler by a message to add some special behaviour to object of class implementing it.

Syntax:

interface marker_interface{

}

Ex. Serializable,Cloneable,Remote Interface

instanceof - to test whether object is an instance of specified type

HomeWork:

create two marker interface - Vehicle & Engine

Create classes

use instanceof operator

class Car{

boolean isVehicle();

}

class Bike{

boolean isVehicle();

}

class Status{

isWorking();

}