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。