设计模式——享元模式

享元模式：运用共享技术有效的支持大量细粒度对象，也就是说在一个系统中如果有多个相同的对象，那么只共享一份就可以了，不必每个都去实例化一个对象。

如果一个应用使用了大量的对象，这些对象造成了很大的系统开销就应该考虑使用享元模式

角色：

抽象享元角色：此角色是所有的具体享元类的超类，为这些类规定出需要实现的公共接口或抽象类。

具体享元(ConcreteFlyweight)角色：实现抽象享元角色所规定的接口。如果有内部状态的话，必须负责为内部状态提供存储空间。

复合享元(UnsharableFlyweight)角色：复合享元角色所代表的对象是不可以共享的，但是一个复合享元对象可以分解成为多个本身是单纯享元对象的组合。

享元工厂(FlyweightFactoiy)角色：本角色负责创建和管理享元角色。本角色必须保证享元对象可以被系统适当地共享。

代码实现：

package com.sun.flyweight;/** * 抽象享元角色 * @author work * */public abstract class FlyWeight {public abstract void operaction(int i);}

package com.sun.flyweight;/** * 具体享元角色 * @author work */public class ConcreteFlyWeight extends FlyWeight{@Overridepublic void operaction(int i) {// TODO Auto-generated method stubSystem.out.println("具体。。。。。。。。"+i);}}

package com.sun.flyweight;/** * 复合享元角色 * @author work * */public class UnShareFlyWeight extends FlyWeight{@Overridepublic void operaction(int i) {// TODO Auto-generated method stubSystem.out.println("不共享具体.........."+i);}}

package com.sun.flyweight;import java.util.Hashtable;/** * 工厂 * @author work */public class FlyWeightFactory {private Hashtable flyHashtable = new Hashtable();public FlyWeightFactory() {// TODO Auto-generated constructor stubflyHashtable.put("X", new ConcreteFlyWeight());flyHashtable.put("Y", new ConcreteFlyWeight());flyHashtable.put("Z", new ConcreteFlyWeight());}public FlyWeight getFlyWeight(String key) {return (FlyWeight) flyHashtable.get(key);}}<pre name="code" class="java">package com.sun.flyweight;/** * 客户端 * @author work */public class Client {public static void main(String[] args) {int ex =22;FlyWeightFactory f = new FlyWeightFactory();FlyWeight f1 = f.getFlyWeight("X");f1.operaction(--ex);FlyWeight f2 = f.getFlyWeight("Y");f2.operaction(--ex);FlyWeight f3 = f.getFlyWeight("Z");f3.operaction(--ex);UnShareFlyWeight u1 = new UnShareFlyWeight();u1.operaction(--ex);}}

改进版代码

package com.sun.flyweight.cg;/** * 抽象享元角色 * @author work * */public abstract class WebSite {<span style="white-space:pre"></span>public abstract void use(User user) ;}

package com.sun.flyweight.cg;/** * 具体享元角色 * @author work * */public class ConcreteWebSite extends WebSite{<span style="white-space:pre"></span><span style="white-space:pre"></span>private String name = "";<span style="white-space:pre"></span><span style="white-space:pre"></span>public ConcreteWebSite(String name) {<span style="white-space:pre"></span>this.name = name;<span style="white-space:pre"></span><span style="white-space:pre"></span>} <span style="white-space:pre"></span><span style="white-space:pre"></span>@Override<span style="white-space:pre"></span>public void use(User user) {<span style="white-space:pre"></span>// TODO Auto-generated method stub<span style="white-space:pre"></span>System.out.println("*******"+name+"**********"+user.getName());<span style="white-space:pre"></span>}}

package com.sun.flyweight.cg;/** * 用户 * @author work * */public class User {<span style="white-space:pre"></span><span style="white-space:pre"></span>private String name;<span style="white-space:pre"></span><span style="white-space:pre"></span>public User(String name) {<span style="white-space:pre"></span>this.name = name;<span style="white-space:pre"></span>}<span style="white-space:pre"></span><span style="white-space:pre"></span>public String getName() {<span style="white-space:pre"></span>return name;<span style="white-space:pre"></span>}}

package com.sun.flyweight.cg;/** * 客户端 * @author work */public class Client {<span style="white-space:pre"></span>public static void main(String[] args) {<span style="white-space:pre"></span>WebSiteFactory wsf = new WebSiteFactory();<span style="white-space:pre"></span>WebSite ws1 = wsf.getWebSite("产品展示");<span style="white-space:pre"></span>ws1.use(new User("张三"));<span style="white-space:pre"></span><span style="white-space:pre"></span>WebSite ws2 = wsf.getWebSite("产品展示");<span style="white-space:pre"></span>ws2.use(new User("王五"));<span style="white-space:pre"></span>}}