Decorator design pattern

README.md

@@ -1,2 +1,32 @@
-# DesignPatternsJava9
-This repo consists Gang of Four Design patterns code on Java 9. Each branch in the repository has code of 1 design pattern. Switch repository to try out different design patterns.
+# What is Decorator Design Pattern 
+Decorator pattern allows a user to add new functionality to an existing object without altering its structure.This pattern creates a decorator class which wraps the original class and provides additional functionality keeping the class methods signature intact.
+
+## Diagram
+![Diagram](https://github.com/premaseem/DesignPatternsJava9/blob/decorator-pattern/diagrams/Decorator%20Pattern%20class%20diagram.jpeg "Diagram")
+
+![Diagram](https://github.com/premaseem/DesignPatternsJava9/blob/decorator-pattern/diagrams/4477491529_462d9dd985_b.jpeg "Diagram")
+
+![Diagram](https://github.com/premaseem/DesignPatternsJava9/blob/decorator-pattern/diagrams/Decorator%20pattern%20sequence%20diagram.png "Diagram")
+
+### When to use Decorator Design Pattern 
+When you want to get rid of too many sub classes by creating separate class for each combination.
+
+### Learn Design Patterns with Java by Aseem Jain
+This repository contains working project code used in video Course by Packt Publication with title "Learn Design Patterns with Java " authored by "Aseem Jain".
+
+### Course link: 
+https://www.packtpub.com/application-development/learn-design-patterns-java-9-video
+
+### ![ http://in.linkedin.com/in/premaseem](https://github.com/premaseem/DesignPatternsJava9/blob/master/linkedin.png "http://in.linkedin.com/in/premaseem") Profile:  http://in.linkedin.com/in/premaseem
+
+### Authors blog on design patterns:
+https://premaseem.wordpress.com/category/computers/design-patterns/
+
+### Software Design pattern community face book page:
+https://www.facebook.com/DesignPatternGuru/
+
+### Note: 
+* This code base will work on Java 9 and above versions. 
+* `diagrams` folders carry UML diagrams.
+* `pattern` folder has code of primary example. 
+* `patternBonus` folder has code of secondary or bonus example.

pattern/src/com/premaseem/Cake.java

@@ -0,0 +1,79 @@
+package com.premaseem;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+public abstract class Cake {
+
+    abstract String getIngredients();
+    abstract double getCost();
+
+}
+
+class VanillaCake extends Cake {
+
+    @Override
+    String getIngredients () {
+        return " Vanilla ";
+    }
+
+    @Override
+    double getCost () {
+        return 2;
+    }
+}
+
+class VanillaCakeWithCandyDecoration extends Cake {
+
+    @Override
+    String getIngredients () {
+        return " Vanilla and Candy ";
+    }
+
+    @Override
+    double getCost () {
+        return 2.4;
+    }
+}
+
+class VanillaCakeWithCandyAndCartoonDecoration extends Cake {
+
+    @Override
+    String getIngredients () {
+        return " Vanilla and candy and cartoon ";
+    }
+
+    @Override
+    double getCost () {
+        return 5.4;
+    }
+}
+
+class VanillaCakeWithCartoonDecoration extends Cake {
+
+    @Override
+    String getIngredients () {
+        return " Vanilla and cartoon ";
+    }
+
+    @Override
+    double getCost () {
+        return 4.4;
+    }
+}
+
+class ChocolateCake extends Cake {
+
+    @Override
+    String getIngredients () {
+        return " Chocolate ";
+    }
+
+    @Override
+    double getCost () {
+        return 3;
+    }
+}
+

pattern/src/com/premaseem/Client.java

@@ -4,10 +4,56 @@
 @author: Aseem Jain
 @title: Design Patterns with Java 9
 @link: https://premaseem.wordpress.com/category/computers/design-patterns/
-@copyright: 2018 Packt Publication
 */
+
 public class Client {
     public static void main (String[] args) {
-        System.out.println("Singleton cook example ");
+        System.out.println("Decorator Pattern example with Cake decoration project");
+
+        // Plain Object
+        Cake cake = new VanillaCake();
+        System.out.println("Plain cake price without decorations - "+ cake.getCost());
+
+        // Decorated Object with addons
+        cake = new CandyDecoration(cake);
+        System.out.println("Cake price with Candy decoration - "+ cake.getCost());
+
+        // Decorated Object with addons
+        // Fun side, price of Cartoon decoration is more then cake itself :-)
+        cake = new CartoonDecoration(cake);
+        cake = new CartoonDecoration(cake);
+        System.out.println("Cake price with double Cartoon decoration - "+cake.getCost());
+
+
+        /* TAKE AWAY:
+        1. Lean code - as its not required to create class for each option
+        2. Price can be calculated dynamically
+        3. Performance improvement
+        4. Loose coupling.
+        5. Easy to update - price of can be updated at one place without touching other classes.
+
+         */
+
+        /* OLD DISCARDED CODE
+        // with decoration
+        cake = new VanillaCakeWithCandyDecoration();
+        System.out.println("Cake price with Candy decoration - "+ cake.getCost());
+
+        // with decoration
+        cake = new VanillaCakeWithCartoonDecoration();
+        System.out.println("Cake price with Cartoon decoration - "+ cake.getCost());
+
+        // with multiple decorations
+        cake = new VanillaCakeWithCandyAndCartoonDecoration();
+        System.out.println("Cake price with Candy and Cartoon decoration - "+ cake.getCost());
+        */
+
+        /*Take Away from Bad Code:
+        1. For each combination/ option there is a static class.
+        2. With less options its ok but in real cake software time application will
+        blow out of proportion due to so many classes.
+        3. Updating price of even one option will impact several classes.
+         */
+
     }
 }

pattern/src/com/premaseem/Decoration.java

@@ -0,0 +1,54 @@
+package com.premaseem;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+
+public abstract class Decoration extends Cake{
+    Cake cake;
+
+    @Override
+    String getIngredients () {
+        return "decoration using different addon items";
+    }
+}
+
+class CandyDecoration extends Decoration{
+
+    Cake baseCake;
+
+    public CandyDecoration (Cake cake) {
+        baseCake = cake;
+    }
+
+    @Override
+    double getCost () {
+        return baseCake.getCost() + .12;
+    }
+
+    @Override
+    String getIngredients () {
+        return "decoration using candies";
+    }
+}
+
+class CartoonDecoration extends Decoration{
+
+    Cake baseCake;
+
+    public CartoonDecoration (Cake cake) {
+        baseCake = cake;
+    }
+
+    @Override
+    double getCost () {
+        return baseCake.getCost() + 2.32;
+    }
+
+    @Override
+    String getIngredients () {
+        return "decoration using candies";
+    }
+}

patternBonus/src/com/premaseem/client/ClientCoffeeBillingMachine.java

@@ -0,0 +1,65 @@
+package com.premaseem.client;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+
+import java.util.Scanner;
+
+import com.premaseem.decorator.AbstractCoffee;
+import com.premaseem.decorator.addons.Chokos;
+import com.premaseem.decorator.addons.Cream;
+import com.premaseem.decorator.addons.Whip;
+import com.premaseem.decorator.basecoffee.ColdCoffee;
+import com.premaseem.decorator.basecoffee.HotCoffee;
+
+public class ClientCoffeeBillingMachine {
+
+	public static void main(String[] args) {
+		Scanner scan = new Scanner(System.in);
+		int repeatRunFlag = 1;
+		while (repeatRunFlag == 1) {
+
+			System.out.println("Welcome to Coffee Billing Machine Project which uses Decorator Design pattern ... ");
+
+			System.out.println("What kind of coffee would you like to have ? ");
+			System.out.println("Press 1 for Hot Coffee ");
+			System.out.println("Press 2 for Cold Coffee ");
+			Integer coffeeType =   scan.nextInt();
+			AbstractCoffee coffee;
+			if(coffeeType == 1){
+				coffee = new HotCoffee();
+			}else{
+				coffee = new ColdCoffee();
+			}
+
+			System.out.println("Do you want Cream ? ");
+			System.out.println("Press 1 for YES and 0 for NO ");
+
+			if(scan.nextInt() == 1){
+				coffee = new Cream(coffee);
+			}
+
+			System.out.println("Do you want Whip ? ");
+			System.out.println("Press 1 for YES and 0 for NO ");
+			if(scan.nextInt() == 1){
+				coffee = new Whip(coffee);
+			}
+
+			System.out.println("Do you want Chokos ? ");
+			System.out.println("Press 1 for YES and 0 for NO ");
+			if(scan.nextInt() == 1){
+				coffee = new Chokos(coffee);
+			}
+
+			System.out.println("Your final order is");
+			System.out.println(coffee.getDescription());
+			System.out.println("Total cost of order is " + coffee.getCost());
+			System.out.println("\n $$$$$$$$$$$$$$$$$$$$  Thanks by Prem Aseem $$$$$$$$$$$$$$$$$$$$$$ \n ");
+			System.out.println("Do you want to Re-run this program - Press 1 for yes and 0 or other digits to EXIT ");
+			repeatRunFlag = scan.nextInt();
+		}
+	}
+}

patternBonus/src/com/premaseem/decorator/AbstractCoffee.java

@@ -0,0 +1,26 @@
+package com.premaseem.decorator;
+
+public abstract class AbstractCoffee {
+
+	String description = " This is HOT/COLD coffee and has xx xx ";
+	String name = "HOT/COLD coffee ";
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public String getDescription() {
+		return description;
+	}
+
+	public void setDescription(String description) {
+		this.description = description;
+	}
+
+	public abstract Double getCost(); 
+}
+

patternBonus/src/com/premaseem/decorator/addons/AddonsOfCoffee.java

@@ -0,0 +1,9 @@
+package com.premaseem.decorator.addons;
+
+import com.premaseem.decorator.AbstractCoffee;
+
+public abstract class AddonsOfCoffee extends AbstractCoffee {
+
+@Override
+abstract public String getDescription();
+}

patternBonus/src/com/premaseem/decorator/addons/Chokos.java

@@ -0,0 +1,23 @@
+package com.premaseem.decorator.addons;
+
+import com.premaseem.decorator.AbstractCoffee;
+
+public class Chokos extends AddonsOfCoffee {
+
+	public AbstractCoffee coffee =null;
+
+	public Chokos(AbstractCoffee abstractCoffee){
+		this.coffee = abstractCoffee;
+	}
+
+	@Override
+	public String getDescription() {
+		return coffee.getDescription() + " chocolate " ;
+	}
+
+	@Override
+	public Double getCost() {
+		return coffee.getCost() + 0.17;
+	}
+
+}

patternBonus/src/com/premaseem/decorator/addons/Cream.java

@@ -0,0 +1,23 @@
+package com.premaseem.decorator.addons;
+
+import com.premaseem.decorator.AbstractCoffee;
+
+public class Cream extends AddonsOfCoffee {
+
+	public AbstractCoffee coffee =null;
+
+	public Cream(AbstractCoffee abstractCoffee){
+		this.coffee = abstractCoffee;
+	}
+
+	@Override
+	public String getDescription() {
+		return coffee.getDescription() + " cream " ;
+	}
+
+	@Override
+	public Double getCost() {
+		return coffee.getCost() + 0.15;
+	}
+
+}