Head First -- 工厂方法

工厂方法模式:定义了一个创建对象的接口,但由子类决定要实例化的类是哪一个。工厂方法让类把实例化推迟到子类。这样，客户程序中关于超类的代码就和子类对象创建代码解耦了。

主要示例代码：

01   public abstract class PizzaStore {
02     public Pizza orderPizza(String type){
03         Pizza pizza = createPizza(type);
04         pizza.prepare();
05         pizza.bake();
06         pizza.cut();
07         pizza.box();
08         return pizza;
09     }
10     abstract Pizza createPizza(String type);
11 }
12
13
14 public abstract class Pizza {
15     String name;
16     String dough;
17     String sauce;
18     void prepare(){
19         System.out.println("prepare pizza");
20     }
21     void bake(){
22         System.out.println("bake pizza");
23     }
24     void cut(){
25         System.out.println("cut pizza");
26     }
27     void box(){
28         System.out.println("box pizza");
29     }
30 }
31
32
33 public class NYStylePizzaStore extends PizzaStore{
34
35     public Pizza createPizza(String type) {
36         Pizza pizza = null;
37         if(type.equals("cheese")){
38             pizza = new NYStyleCheesePizza();
39         }else if(type.equals("veggie")){
40             pizza = new NYStyleVeggiePizza();
41         }
42         else if(type.equals("clam")){
43             pizza = new NYStyleClamPizza();
44         }
45         return pizza;
46     }