/概述/////使用工厂模式后Meeting2不用修改，开会只需修改工厂MeetingDao的返回类即可。public class MeetingDao {  public static TalImp getTalkInstance(){   return new TalkInChina();  }}public class Meeting2 {   public void doMeeting(TalImp talk){    talk.say();   }   public static void main(String args[]){    TalImp talk=MeetingDao.getTalkInstance();    Meeting2 meeting=new Meeting2();    meeting.doMeeting(talk);   }}