java计算两个日期间隔方法

SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");   Date d1 = null;   try{   d1 = formatter.parse(input);   }catch(ParseException e){   out.println("unparseable using " + formatter);   }   Date d2 = new Date();   long diff = d2.getTime() - d1.getTime();   out.println("Difference is " + (diff/(1000*60*60*24)) + " days.");