设计模式之享元模式

享元模式，刚好现在共享单车火，拿来开刀

享元模式UML.png

interface ShareBike{
    void ride();
}

抽象共享单车

class ShareBikeOFO implements ShareBike{
    public void ride(){
        //小黄车驾到
    }
}

天朝小黄车

class ShareBikeMoBai implements ShareBike{
    public void ride(){
        //摩拜单车
    }
}

50斤的摩拜单车

class BikeType{
    public static final String OFO = "OFO";
    public static final String MOBAI = "MOBAI";
}

共享单车类型

class ShareBikeFactory{
    HashMap shareBikeMaps = new HashMap();
    
    public ShareBikeFactory(){
        shareBikeFactory.put("BikeType.OFO",new ShareBikeOFO());
        shareBikeFactory.put("BikeType.MOBAI",new ShareBikeMoBai());
    }
    
    public ShareBike getShareBike(String type){
        if(BikeType.OFO.equals(type)){
            return (ShareBikeOFO)shareBikeMaps.get(type);
        }else if(BikeType.MOBAI.equals(type){
            return (ShareBikeMOBAI)shareBikeMaps.get(type);
        }
        return null;
    }
}

单车托管所

public class Client{
    public static void main(String args[]){
        ShareBikeFactory mshareBikeFactory = new ShareBikeFactory();
        ShareBike shareBikeOFO,shareBikeMobai;
        shareBikeOFO  = mshareBikeFactory.get(BikeType.OFO);
        shareBikeMoBai  = mshareBikeFactory.get(BikeType.MOBAI);
        shareBikeOFO.ride();
        shareBikeMoBai.ride();
    }
}

客户端根据需求拿单车来骑车

个人总结

享元模式是为了避免大量创建对象省内存时候用的，Android中消息机制中Message用链表来存储消息实现消息复用就是用到这种模式。