Java 時間比較

Date nowTime = new Date(System.currentTimeMillis());
			  SimpleDateFormat sdFormatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
			  String ret = sdFormatter.format(nowTime);  
			
			 SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
			   java.util.Date now = df.parse(ret);
			   java.util.Date date=df.parse(shijian);
			   long l=now.getTime()-date.getTime();
			   long day=l/(24*60*60*1000);
			   long hour=(l/(60*60*1000)-day*24);
			   long min=((l/(60*1000))-day*24*60-hour*60);
			   long s=(l/1000-day*24*60*60-hour*60*60-min*60);
			   System.out.println(""+day+"天"+hour+"小時"+min+"分"+s+"秒");
			   int a=(int)(day+hour+min);

對時間進行加減，來判斷數據庫取到的 shijian這個值 和系統當前時間相差多少