Decoretor Pattern

Intent

Attach additional responsibilities to an object dynamically. Decorators provide
a flexible alternative to subclassing for extending functionality.

                              Also Known As

Wrapper

                              Applicability

Use Decorator

                      

•   to add responsibilities to individual objects dynamically and
  transparently, that is, without affecting other objects.
•  for responsibilities that can be withdrawn.
•  when extension by subclassing is impractical. Sometimes a large number of
  independent extensions are possible and would produce an explosion of
  subclasses to support every combination. Or a class definition may be hidden
  or otherwise unavailable for subclassing.

                                  Structure

Class Diagram

Program

 ====================Interface class=======================

package DecoratorPattern;

/**
 *
 * @author Sonu
 */
public interface IceCream {
   public double getCost();
   public String getDiscription();
}

==================== Abstract Class =======================

package DecoratorPattern;

/**
 *
 * @author Sonu
 */
public abstract class Decoretor implements IceCream{

    IceCream i;
    public Decoretor(IceCream i1) {
        i=i1;  
    }
   
    @Override
    public double getCost() {
        return i.getCost();
    }

    @Override
    public String getDiscription() {
        return i.getDiscription();
    }
   
}

================concreate class =======================

package DecoratorPattern;

/**
 *
 * @author Sonu
 */
public class Chocklate extends Decoretor{

    public Chocklate(IceCream i1) {
        super(i1);
    }
    public double getCost()
    {
        return super.getCost()+10;
    }
    public String getDiscription()
    {
        return super.getDiscription()+"With Chocklate";
    }
}

====================concreate class ====================

package DecoratorPattern;

/**
 *
 * @author Sonu
 */
public class Nutes extends Decoretor{

    public Nutes(IceCream i1) {
        super(i1);
    }
    @Override
    public double getCost()
    {
        return super.getCost()+20;
    }
    @Override
    public String getDiscription()
    {
        return super.getDiscription()+"With Nutes";
    }

}

=====================Concreate Class======================

package DecoratorPattern;

/**
 *
 * @author Sonu
 */
public class StrawbarryIceCream implements IceCream{

    @Override
    public double getCost() {
        return 15;
    }

    @Override
    public String getDiscription() {
        return "Add Strawbarry IceCream";
    }
   
}

===================Concreate Class========================

package DecoratorPattern;

/**
 *
 * @author Sonu
 */
public class VanillaIceCream implements IceCream{

    @Override
    public double getCost() {
     return 5.5;  
    }

    @Override
    public String getDiscription() {
        return "This is Vanilla IceCreame.";
    }
   
}

=================The main class =======================

package DecoratorPattern;

import java.util.Scanner;

/**
 *
 * @author Sonu
 */
public class Main {
    public static void main(String[] args) {
        System.out.println("Enter your Choise:");
        System.out.println("1.Vanilla IceCream.");
        System.out.println("2.Strawbarry IceCream");
        System.out.println("3.Vanilla IceCream with Chockalte.");
        System.out.println("4.Vanilla IceCream with Nutes.");
        System.out.println("5.Strawbarry IceCream with Chockalte.");
        System.out.println("6.Strawbarry IceCream with Nutes.");
        Scanner scanner = new Scanner(System.in);
        int i = scanner.nextInt();
        switch(i)
        {
            case 1:
                 IceCream ic = new VanillaIceCream();
                 System.out.println("Total Cost:"+ic.getCost());
                 System.out.println(""+ic.getDiscription());
                break;
            case 2:
                 ic = new StrawbarryIceCream();
                System.out.println("Total Cost:"+ic.getCost());
                System.out.println(""+ic.getDiscription());
                break;
            case 3:
                ic = new Chocklate((IceCream)new VanillaIceCream());
                System.out.println("Total Cost:"+ic.getCost());
                System.out.println(""+ic.getDiscription());
                break;
            case 4:
                ic = new Nutes((IceCream)new VanillaIceCream());
                System.out.println("Total Cost:"+ic.getCost());
                System.out.println(""+ic.getDiscription());
                break;
            case 5:
                ic = new Chocklate((IceCream)new StrawbarryIceCream());
                System.out.println("Total Cost:"+ic.getCost());
                System.out.println(""+ic.getDiscription());
                break;
            case 6:
                ic = new Nutes((IceCream)new StrawbarryIceCream());
                System.out.println("Total Cost:"+ic.getCost());
                System.out.println(""+ic.getDiscription());
                break;
                default:
                    System.out.println("You Chose Wrong Option.");
        }
    }
}

======================== output =====================

Output