3，享元工厂类中实例化一个对象是具体的享元对象，而非抽象享元类；

/**
 * Created by tory on 2018/1/4.
 * 享元模式
 */
public class FlyweightPattern {
    public static void main(String[] args) {
        WallBuilder wb = FlyweightFactory.get("green");
        wb.build();
        wb = FlyweightFactory.get("red");
        wb.build();
        wb = FlyweightFactory.get("green");
        wb.build();
    }
}

//Flyweight 抽象享元类
interface Flyweight {
    void build();
}

//Concreteflyweight 具体享元类
class WallBuilder implements Flyweight {
    //内部状态
    String color;

    WallBuilder(String color) {
        this.color = color;
    }

    @Override
    public void build() {
        System.out.println("修了一睹" + color + "的墙");
    }
}

//FlyweightFactory 享元工厂类
class FlyweightFactory {
    //String为外部状态
    static Map<String, WallBuilder> map = new HashMap();

    public static WallBuilder get(String key) {
        WallBuilder t = map.get(key);
        if (null == t) {
            //注意这里是具体享元类，不能是抽象享元类
            t = new WallBuilder(key);
            map.put(key, t);
        }
        return t;
    }
}