public int compareTo(BUserDynamic o) {
        try{
            Date dt1 = sdf.parse(u_dynamic_time);
            Date dt2 = sdf.parse(o.u_dynamic_time);
            if(dt1.getTime()>dt2.getTime()){
                return -1;
            }else if(dt1.getTime()<dt2.getTime()){
                return 1;
            }else{
                return 0;
            }
        } catch (java.text.ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return 0;
    }