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.");