Head First设计模式-工厂模式

一、整体代码

       PizzaStore.java

public abstract class PizzaStore {
 
	abstract Pizza createPizza(String item);//面向抽象编程，对扩展开放，对修改封闭。
 
	public Pizza orderPizza(String type) {
		Pizza pizza = createPizza(type);
		System.out.println("--- Making a " + pizza.getName() + " ---");
		pizza.prepare();//面向抽象编程
		pizza.bake();
		pizza.cut();
		pizza.box();
		return pizza;
	}
}

        NYPizzaStore.java

public class NYPizzaStore extends PizzaStore {

	Pizza createPizza(String item) {
		if (item.equals("cheese")) {
			return new NYStyleCheesePizza();
		} else if (item.equals("clam")) {
			return new NYStyleClamPizza();
		}  else return null;
	}
}

        ChicagoPizzaStore.java

public class ChicagoPizzaStore extends PizzaStore {

	Pizza createPizza(String item) {
        	if (item.equals("cheese")) {
            		return new ChicagoStyleCheesePizza();
        	} else if (item.equals("clam")) {
        	    	return new ChicagoStyleClamPizza();
        	}  else return null;
	}
}

       Pizza.java

import java.util.ArrayList;

public abstract class Pizza {
	String name;
	String dough;
	String sauce;
	ArrayList toppings = new ArrayList();
 
	void prepare() {
		System.out.println("Preparing " + name);
		System.out.println("Tossing dough...");
		System.out.println("Adding sauce...");
		System.out.println("Adding toppings: ");
		for (int i = 0; i < toppings.size(); i++) {
			System.out.println("   " + toppings.get(i));
		}
	}
  
	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");
	}
 
	public String getName() {
		return name;
	}

	public String toString() {
		StringBuffer display = new StringBuffer();
		display.append("---- " + name + " ----\n");
		display.append(dough + "\n");
		display.append(sauce + "\n");
		for (int i = 0; i < toppings.size(); i++) {
			display.append((String )toppings.get(i) + "\n");
		}
		return display.toString();
	}
}

      ChicagoStyleCheesePizza.java

public class ChicagoStyleCheesePizza extends Pizza {

	public ChicagoStyleCheesePizza() { 
		name = "Chicago Style Deep Dish Cheese Pizza";
		dough = "Extra Thick Crust Dough";
		sauce = "Plum Tomato Sauce";
 
		toppings.add("Shredded Mozzarella Cheese");
	}
 
	void cut() {
		System.out.println("Cutting the pizza into square slices");
	}
}

       ChicagoStyleClamPizza.java

public class ChicagoStyleClamPizza extends Pizza {
	public ChicagoStyleClamPizza() {
		name = "Chicago Style Clam Pizza";
		dough = "Extra Thick Crust Dough";
		sauce = "Plum Tomato Sauce";
 
		toppings.add("Shredded Mozzarella Cheese");
		toppings.add("Frozen Clams from Chesapeake Bay");
	}
 
	void cut() {
		System.out.println("Cutting the pizza into square slices");
	}
}

        NYStyleCheesePizza.java

public class NYStyleCheesePizza extends Pizza {

	public NYStyleCheesePizza() { 
		name = "NY Style Sauce and Cheese Pizza";
		dough = "Thin Crust Dough";
		sauce = "Marinara Sauce";
 
		toppings.add("Grated Reggiano Cheese");
	}
}

          NYStyleClamPizza.java

public class NYStyleClamPizza extends Pizza {

	public NYStyleClamPizza() {
		name = "NY Style Clam Pizza";
		dough = "Thin Crust Dough";
		sauce = "Marinara Sauce";
 
		toppings.add("Grated Reggiano Cheese");
		toppings.add("Fresh Clams from Long Island Sound");
	}
}

         PizzaTestDrive.java

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.getName() + "\n");
 
		pizza = chicagoStore.orderPizza("cheese");
		System.out.println("Joel ordered a " + pizza.getName() + "\n");

		pizza = nyStore.orderPizza("clam");
		System.out.println("Ethan ordered a " + pizza.getName() + "\n");
 
		pizza = chicagoStore.orderPizza("clam");
		System.out.println("Joel ordered a " + pizza.getName() + "\n");

	}
}

二、总结

     1、工厂方法模式定义了对象的接口，但由子类决定实例化的类是哪一个。工厂方法模式让类的实例化推迟到子类。

     2、抽象类和接口可以实现多态，这样才保证了面向对象的可扩展性，封装变化，松耦合等特性。设计模式几乎都在与抽象类和接口打交到，用的越多，程序可扩展性越好。