java计算两个日期相差天数

 public static void main(String[] args) throws ParseException {  
            // TODO Auto-generated method stub  
            SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  
            Date d1=sdf.parse("2015-07-01 10:10:10");  
            Date d2=sdf.parse("2015-09-15 00:00:00");  
            System.out.println(daysBetween(d1,d2));  
            System.out.println(daysBetween("2012-09-08 10:10:10","2012-09-15 00:00:00"));  
        }  

        /**  
         * 计算两个日期之间相差的天数  
         * @param smdate 较小的时间 
         * @param bdate  较大的时间 
         * @return 相差天数 
         * @throws ParseException  
         */    
        public static int daysBetween(Date smdate,Date bdate) throws ParseException    
        {    
            SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");  
            smdate=sdf.parse(sdf.format(smdate));  
            bdate=sdf.parse(sdf.format(bdate));  
            Calendar cal = Calendar.getInstance();    
            cal.setTime(smdate);    
            long time1 = cal.getTimeInMillis();                 
            cal.setTime(bdate);    
            long time2 = cal.getTimeInMillis();         
            long between_days=(time2-time1)/(1000*3600*24);  

           return Integer.parseInt(String.valueOf(between_days));           
        }    

    /** 
    *字符串的日期格式的计算 
    */  
        public static int daysBetween(String smdate,String bdate) throws ParseException{  
            SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");  
            Calendar cal = Calendar.getInstance();    
            cal.setTime(sdf.parse(smdate));    
            long time1 = cal.getTimeInMillis();                 
            cal.setTime(sdf.parse(bdate));    
            long time2 = cal.getTimeInMillis();         
            long between_days=(time2-time1)/(1000*3600*24);  

           return Integer.parseInt(String.valueOf(between_days));     
        }