Inheritance in Object Orient Programming and Java

Inheritance
Its a process where one object acquire properites another.
Inheritence reduces the code re-usablity.

Inheritence can be achieved by using extends or implemnts keyword

Single Inheritance:
Class A extends B{
statements
}

Example:
=============
Pulsar is subclass of Bike
TVS is subclass of Bike.

package com.oops;

class TwoWheeler{

int count=1;

public void setProp(){
System.out.println("Color: Red & Brand:Own");
}

}
public class SingleInheritence extends TwoWheeler {

public static void main(String args[]){
TwoWheeler two=new TwoWheeler();
SingleInheritence si=new SingleInheritence();

System.out.println(si instanceof TwoWheeler);
System.out.println("Calling method in SuperClass");
si.setProp();
}
}

Output
=======
true
Calling method in SuperClass
Color: Red & Brand:Own

Multiple Inheritance can be acheived by using interface. 

Interface in Java Language (Click on link to know about interfaces)

Below example contains Single Inheritance and Multiple Inheritance Using Interfaces.

package com.oops;

class TwoWheeler{

int count=1;

public void setProp(){
System.out.println("Color: Red & Brand:Own");
}

}

interface Car
{
   public void setBrandname(String name);
}

interface HeaveyVechile{

public void setProperites(String prop);
}

public class Wheeler extends TwoWheeler implements Car, HeaveyVechile{


public static void main(String args[]){

TwoWheeler two=new TwoWheeler();
Wheeler si=new Wheeler();

System.out.println(si instanceof TwoWheeler);
System.out.println("Calling method in SuperClass");
si.setProp();
si.setBrandname("First");
si.setProperites("HeavyLoadVechile");
}

@Override
public void setBrandname(String name) {
System.out.println("Brand name is"+name);

}

@Override
public void setProperites(String prop) {
System.out.println("Heavy Vechile with 4 or 8 Wheels "+prop);


}

}

Output
=========
true
Calling method in SuperClass
Color: Red & Brand:Own
Brand name isFirst
Heavy Vechile with 4 or 8 Wheels HeavyLoadVechile

interfaces in Object Oriented Programming Language

interface
==========
Descriptive set of methods. Implements class needs to be implemented methods in interface.

Properties of interface:
=========================
Canot mark interface as final
Cannot instiate interface.
Default: Methods in interface are abstract
fields in interface are static and final.
interface can implement class.
interface can extend multiple interfaces.

Class Implementing Interface
============================
package com.oops;

interface Bike{

//final static fields as default
int Capacity=150;

//abstract  methods as default
public void speed();
public void price();
}
public class InterfaceExample implements Bike {

@Override
public void speed() {
System.out.println("Speed of Bike is 100 KMPH");

}

@Override
public void price() {
System.out.println("Price of Bike is 75K");

}

public static void main(String args[]){

InterfaceExample it=new InterfaceExample();
it.speed();
it.price();
}

}

Interface extends Multiple Interfaces

public interface Computer
{
   public void setBrandname(String name);
}

public interface Desktop extends Computer
{
   public void setProperty(String prop);
   public void viewProperty(String id);
}

public interface Laptop extends Computer
{
   public void setProcess(double process);
   public void setScreen(int size);
}

public interface Laptop extends Computer,Device{

statements
}