享元模式，剛好現(xiàn)在共享單車火，拿來(lái)開(kāi)刀

享元模式UML.png

interface ShareBike{
    void ride();
}

抽象共享單車

class ShareBikeOFO implements ShareBike{
    public void ride(){
        //小黃車駕到
    }
}

天朝小黃車

class ShareBikeMoBai implements ShareBike{
    public void ride(){
        //摩拜單車
    }
}

50斤的摩拜單車

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

共享單車類型

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;
    }
}

單車托管所

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();
    }
}

客戶端根據(jù)需求拿單車來(lái)騎車

個(gè)人總結(jié)

享元模式是為了避免大量創(chuàng)建對(duì)象省內(nèi)存時(shí)候用的，Android中消息機(jī)制中Message用鏈表來(lái)存儲(chǔ)消息實(shí)現(xiàn)消息復(fù)用就是用到這種模式。