享元模式（Flyweight），運用共享技術有效地支持大量細粒度的對象恒序。
PS:比如String的對象三圆，利用享元模式概念，兩個棧指針指向同一個堆地址污呼。
享元模式可以避免大量非常相似類的開銷裕坊。在程序設計中，有時需要生產(chǎn)大量細粒度的類實例來表示數(shù)據(jù)燕酷。如果能發(fā)現(xiàn)這些實例除了幾個參數(shù)之外基本都是相同的籍凝，有時就能受大幅度地減少需要實例化的類的數(shù)量。如果能把那些參數(shù)移到類實例的外面苗缩，在方法調用時將它們傳遞進來饵蒂，就可以通過共享大幅度地減少單實例的數(shù)目。

主方法

public class main {
    public static void main(String[] args) {
        WebSiteFactory webSiteFactory = new WebSiteFactory();

        WebSite fx = webSiteFactory.getWebSiteCategory("產(chǎn)品展示");
        fx.use(new User("小菜"));

        WebSite fy = webSiteFactory.getWebSiteCategory("產(chǎn)品展示");
        fy.use(new User("大鳥"));

        WebSite fz = webSiteFactory.getWebSiteCategory("產(chǎn)品展示");
        fz.use(new User("嬌嬌"));

        WebSite fl = webSiteFactory.getWebSiteCategory("博客");
        fl.use(new User("老頑童"));

        WebSite fm = webSiteFactory.getWebSiteCategory("博客");
        fm.use(new User("桃谷六仙"));

        WebSite fn = webSiteFactory.getWebSiteCategory("博客");
        fn.use(new User("南海鱷神"));

        System.out.println(String.format("得到網(wǎng)站分類總數(shù)為：{%d}", webSiteFactory.countWebSite()));
    }
}

用戶類

public class User {
    public User(String name) {
        this.name = name;
    }

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

享元抽象類

/**
 * 網(wǎng)站抽象類
 */
public abstract class WebSite {
    public abstract void use(User user);
}

享元實現(xiàn)類

/**
 * 具體網(wǎng)站類
 */
public class WebSiteImpl extends WebSite {
    private String name = "";

    public WebSiteImpl(String name) {
        this.name = name;
    }

    public void use(User user) {
        System.out.println("網(wǎng)站分類：" + name + " 用戶：" + user.getName());
    }
}

享元工廠類

import java.util.concurrent.ConcurrentHashMap;
public class WebSiteFactory {
    private ConcurrentHashMap<String, WebSiteImpl> flyweights = new ConcurrentHashMap<String, WebSiteImpl>();

    public WebSite getWebSiteCategory(String key) {
        if (!flyweights.contains(key)) {
            flyweights.put(key, new WebSiteImpl(key));
        }
        return flyweights.get(key);
    }

    public int countWebSite() {
        return flyweights.size();
    }
}