结构型模式之享元模式

Posted 2020-11-20 756623607-zhang

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GitHub地址：https://github.com/zhangboqing/design-mode/tree/master/src/main/java/com/zbq

一.定义

　　享元模式(Flyweight Pattern)：运用共享技术有效地支持大量细粒度对象的复用。系统只使用少量的对象，而这些对象都很相似，状态变化很小，可以实现对象的多次复用。由于享元模式要求能够共享的对象必须是细粒度对象，因此它又称为轻量级模式，它是一种对象结构型模式。

二、模式结构成员构成

? Flyweight: 抽象享元类

? ConcreteFlyweight: 具体享元类

? UnsharedConcreteFlyweight: 非共享具体享元类

? FlyweightFactory: 享元工厂类

技术分享图片

三.代码示例

 1 /**
 2  * Flyweight
 3  * 抽象享元类
 4  */
 5 public interface Flyweight {
 6     //一个示意性方法，参数state是外蕴状态
 7     public void operation(String state);
 8 }
 9 
10 /**
11  * ConcreteFlyweight
12  * 具体享元类
13  */
14 public class ConcreteFlyweight implements Flyweight {
15     //代表内部状态
16     private Character intrinsicState = null;
17     /**
18      * 构造函数，内蕴状态作为参数传入
19      * @param state
20      */
21     public ConcreteFlyweight(Character state){
22         this.intrinsicState = state;
23     }
24     
25     
26     /**
27      * 外蕴状态作为参数传入方法中，改变方法的行为，
28      * 但是并不改变对象的内蕴状态。
29      */
30     @Override
31     public void operation(String state) {
32         // TODO Auto-generated method stub
33         System.out.println("Intrinsic State = " + this.intrinsicState);
34         System.out.println("Extrinsic State = " + state);
35     }
36 
37 }
38 
39 /**
40  * FlyweightFactory
41  * 享元工厂类
42  */
43 public class FlyweightFactory {
44     private Map<Character,Flyweight> files = new HashMap<Character,Flyweight>();
45     
46     public Flyweight factory(Character state){
47         //先从缓存中查找对象
48         Flyweight fly = files.get(state);
49         if(fly == null){
50             //如果对象不存在则创建一个新的Flyweight对象
51             fly = new ConcreteFlyweight(state);
52             //把这个新的Flyweight对象添加到缓存中
53             files.put(state, fly);
54         }
55         return fly;
56     }
57 }
58 
59 /**
60  * client
61  */
62 public class Client {
63 
64     public static void main(String[] args) {
65         // TODO Auto-generated method stub
66         FlyweightFactory factory = new FlyweightFactory();
67         Flyweight fly = factory.factory(new Character(‘a‘));
68         fly.operation("First Call");
69         
70         fly = factory.factory(new Character(‘b‘));
71         fly.operation("Second Call");
72         
73         fly = factory.factory(new Character(‘a‘));
74         fly.operation("Third Call");
75     }
76 
77 }