享元模式

享元模式是对象的结构模式。享元模式以共享的方式高效地支持大量的细粒度对象。

import java.util.HashMap;
import java.util.Map;

//抽象享元接口
interface Flyweight{
    //state参数为外蕴状态
    public void method(String state);
}

//具体享元类
class ConcreteFlyweight implements Flyweight{

    private String inState;
    
    //内蕴状态作为参数传入
    public ConcreteFlyweight(String inState){
        this.inState = inState;
    }
    
    @Override
    public void method(String state) {
        System.out.println("外蕴状态" + state);
        System.out.println("内蕴状态" + inState);
    }
    
}

//享元工厂类
class FlyweightFactory{
    
    private Map<String, Flyweight> flies = new HashMap<String, Flyweight>();
    
    public Flyweight factory(String inState){
        //从缓存中查询有没有指定的变量
        Flyweight fly = flies.get(inState);
        if(null == fly){
            fly = new ConcreteFlyweight(inState);
            flies.put(inState, fly);
        }
        return fly;
    }
}