Newthinktank Com Videos Design Patterns Tutorial

Factory Design Pattern Tutorial

Posted by on Sep 1, 2012 in Java Video Tutorial | 37 comments

Welcome to my Factory design pattern tutorial. This is a continuation of my design patterns video tutorial.

You use the Factory design pattern when you want to define the class of an object at runtime. It also allows you to encapsulate object creation so that you can keep all object creation code in one place.

The Factory pattern is presented in many ways to help you learn. Refer to the code that follows the video to completely understand it.

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Code from the Video

ENEMYSHIP.JAVA

public abstract class EnemyShip { 	 	private String name; 	private double speed; 	private double directionX; 	private double directionY; 	private double amtDamage; 	 	public String getName() { return name; } 	public void setName(String newName) { name = newName; } 	 	public double getDamage() { return amtDamage; } 	public void setDamage(double newDamage) { amtDamage = newDamage; } 	 	public void followHeroShip(){ 		 		System.out.println(getName() + " is following the hero"); 		 	} 	 	public void displayEnemyShip(){ 		 		System.out.println(getName() + " is on the screen"); 		 	} 	 	public void enemyShipShoots() { 		 		System.out.println(getName() + " attacks and does " + getDamage() + " damage to hero"); 		 	} 	 }

UFOENEMYSHIP.JAVA

public class UFOEnemyShip extends EnemyShip { 	 	public UFOEnemyShip(){ 		 		setName("UFO Enemy Ship"); 		 		setDamage(20.0); 		 	} 	 }

ROCKETENEMYSHIP.JAVA

public class RocketEnemyShip extends EnemyShip { 	 	public RocketEnemyShip(){ 		 		setName("Rocket Enemy Ship"); 		 		setDamage(10.0); 		 	} 	 }

ENEMYSHIPTESTING.JAVA

import java.util.Scanner;  public class EnemyShipTesting {  	public static void main(String[] args){ 		 		// Create the factory object 		EnemyShipFactory shipFactory = new EnemyShipFactory(); 		 		// Enemy ship object 		 		EnemyShip theEnemy = null; 		 		Scanner userInput = new Scanner(System.in); 		 		System.out.print("What type of ship? (U / R / B)"); 		 		if (userInput.hasNextLine()){ 			 			String typeOfShip = userInput.nextLine(); 		 			theEnemy = shipFactory.makeEnemyShip(typeOfShip); 			 			if(theEnemy != null){ 				 				doStuffEnemy(theEnemy); 				 			} else System.out.print("Please enter U, R, or B next time"); 		 		} 		 		/* 		EnemyShip theEnemy = null; 		 		// Old way of creating objects 		// When we use new we are not being dynamic 		 		EnemyShip ufoShip = new UFOEnemyShip(); 		 		doStuffEnemy(ufoShip); 		 		System.out.print("\n"); 		 		// ----------------------------------------- 		 		// This allows me to make the program more dynamic 		// It doesn't close the code from being modified 		// and that is bad! 		 		// Defines an input stream to watch: keyboard 		Scanner userInput = new Scanner(System.in); 		 		String enemyShipOption = ""; 		 		System.out.print("What type of ship? (U or R)"); 		 		if (userInput.hasNextLine()){ 			 			enemyShipOption = userInput.nextLine(); 			 		} 		 		if (enemyShipOption == "U"){ 			 			theEnemy = new UFOEnemyShip();  			 		} else  		 		if (enemyShipOption == "R"){ 			 			theEnemy = new RocketEnemyShip(); 			 		} else { 			 			theEnemy = new BigUFOEnemyShip(); 			 		} 		 		doStuffEnemy(theEnemy); 		 		// -------------------------------------------- 		*/ 		 	} 	 	// Executes methods of the super class 	 	public static void doStuffEnemy(EnemyShip anEnemyShip){ 		 		anEnemyShip.displayEnemyShip(); 		 		anEnemyShip.followHeroShip(); 		 		anEnemyShip.enemyShipShoots(); 		 	} 	 }

BIGUFOENEMYSHIP.JAVA

public class BigUFOEnemyShip extends UFOEnemyShip { 	 	public BigUFOEnemyShip(){ 		 		setName("Big UFO Enemy Ship"); 		 		setDamage(40.0); 		 	} 	 }

ENEMYSHIPFACTORY.JAVA

// This is a factory thats only job is creating ships // By encapsulating ship creation, we only have one // place to make modifications  public class EnemyShipFactory{ 	 	// This could be used as a static method if we 	// are willing to give up subclassing it 	 	public EnemyShip makeEnemyShip(String newShipType){ 		 		EnemyShip newShip = null; 		 		if (newShipType.equals("U")){ 			 			return new UFOEnemyShip(); 			 		} else  		 		if (newShipType.equals("R")){ 			 			return new RocketEnemyShip(); 			 		} else  		 		if (newShipType.equals("B")){ 			 			return new BigUFOEnemyShip(); 			 		} else return null; 		 	} 	 }

Factory Design Pattern Diagram

Factory Design Pattern