code: public static String addZerosBefore(String orderNo, int count) {
  
          if (orderNo == null) {
              return "";// orderNo = "";
          }
  
          if (orderNo.length() > count) {
              orderNo = "?" + orderNo.substring(orderNo.length() - count - 1, orderNo.length() - 1);
          } else {
  
              int le = orderNo.length();
  
              for (int i = 0; i < count - le; i++) {
                  orderNo = "0" + orderNo;
              }
  
          }
  
          return orderNo;
      }
docs: Method addZerosBefore.
  
  @param orderNo
  @param count
  @return String