Abstract Factory Pattern

The Abstract Factory Pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes.

Abstract Factory Pattern diagram

Implementation

Creating an Abstract Factory interface:

public interface PizzaIngredientFactory {
	public Dough createDough();
	public Sauce createSauce();
	public Cheese createCheese();
	public Veggies[] createVeggies();
	public Pepperoni createPepperoni();
	public Clam createClam();
}

Creating a Concrete Factory:

public class NYPizzaIngredientFactory implements PizzaIngredientFactory {
	/* Provide concrete products of ingredients */
	public Dough createDough() {
		return new ThinCrustDough();
	}
	
	public Sauce createSauce() {
		return new MarinaraSauce();
	}
	
	public Cheese createCheese() {
		return new ReggianoCheese();
	}
	
	public Veggies[] createVeggies() {
		Veggies veggies[] = {new Garlic(), new Onion(), new Mushroom(), new RedPepper()};
		return veggies;
	}
 
	public Pepperoni createPepperoni() {	
		return new SlicedPepperoni();
	}
	
	public Clam createClam() {
		return new FreshClam();
	}
}

Reworking Pizza Product:
In this case, this becomes an Abstract Product.

public abstract class Pizza {
 
	String name;
	Dough dough;
	Sauce sauce;
	Veggies veggies[];
	Cheese cheese;
	Pepperoni pepperoni;
	Clam clam;
	
	/* Concreate Product is responsible how to prepare pizzas */
	abstract void prepare();
	
	void bake() {
		System.out.println("Bake for 25 minutes at 350");
	}
	
	void cut() {
		System.out.println("Cutting the pizza into diagonal slices");
	}  
	
	void box() {
		System.out.println("Place pizza in official PizzaStore box");
	}
	
	void setName(String name) {
		this.name = name;
	}
	
	String getName() {
		return name;
	}
	
	public String toString() {
		StringBuffer result = new StringBuffer();
		result.append("---- " + name + " ----\n");
		if (dough != null) {
			result.append(dough);
			result.append("\n");
		}
	
		if (sauce != null) {
			result.append(sauce);
			result.append("\n");
		}
	
		if (cheese != null) {
			result.append(cheese);
			result.append("\n");
		}
	
		if (veggies != null) {
			for (int i = 0; i < veggies.length; i++) {
				result.append(veggies[i]);
				if (i < veggies.length-1) {
					result.append(", ");
				}
			}
			result.append("\n");
		}
		
		if (clam != null) {
			result.append(clam);
			result.append("\n");
		}
		
		if (pepperoni != null) {
			result.append(pepperoni);
			result.append("\n");
		}
		
		return result.toString();
	}
}

Creating a Concrete Product:
As you can see below, the client NYPizzaStore uses NYPizzaIngredientFactory to create these products.

public class CheesePizza extends Pizza {
 
	/* Now pizza store relies on factory to prepare ingredients */
	PizzaIngredientFactory ingredientFactory;
 
	public CheesePizza(PizzaIngredientFactory ingredientFactory) {
		this.ingredientFactory = ingredientFactory;
	}
 
	void prepare() {
		System.out.println("Preparing " + name);
		dough = ingredientFactory.createDough();
		sauce = ingredientFactory.createSauce();	
		cheese = ingredientFactory.createCheese();
	}
 
}

Reworking Pizza stores:
In this case, NYPizzaStore is the client.

public class NYPizzaStore extends PizzaStore {
 
	protected Pizza createPizza(String item) {
		Pizza pizza = null;	
		/* Client of NYPizzaIngredientFactory*/*		
		PizzaIngredientFactory ingredientFactory = new NYPizzaIngredientFactory();
		
		/* Rely on the factory to create concrete products. */
		if (item.equals("cheese")) {
			pizza = new CheesePizza(ingredientFactory);
			pizza.setName("New York Style Cheese Pizza");
		} else if (item.equals("veggie")) {
			pizza = new VeggiePizza(ingredientFactory);
			pizza.setName("New York Style Veggie Pizza");
		} else if (item.equals("clam")) {
			pizza = new ClamPizza(ingredientFactory);
			pizza.setName("New York Style Clam Pizza");
		} else if (item.equals("pepperoni")) {
			pizza = new PepperoniPizza(ingredientFactory);
			pizza.setName("New York Style Pepperoni Pizza");
		}
		return pizza;
	}
}

Testing:

public class PizzaTestDrive {
	public static void main(String[] args) {
		PizzaStore nyStore = new NYPizzaStore();
		PizzaStore chicagoStore = new ChicagoPizzaStore();
		
		Pizza pizza = nyStore.orderPizza("cheese");
		System.out.println("Ethan ordered a " + pizza + "\n");
		pizza = chicagoStore.orderPizza("cheese");
		System.out.println("Joel ordered a " + pizza + "\n");
		
		pizza = nyStore.orderPizza("clam");
		System.out.println("Ethan ordered a " + pizza + "\n");
		pizza = chicagoStore.orderPizza("clam");
		System.out.println("Joel ordered a " + pizza + "\n");
	}
}