private int[] parseBookingID(String bookingID)
    {
        int[] idArray = null;
        try
        {
            // exit if bookingID is empty
            if (bookingID == null || bookingID.length() == 0) {
                return null;
            }

            int MAX_ATTR = 2;    // 2 members: resID_reservationID
            String[] list = bookingID.split("_");

            if (list.length != MAX_ATTR) {
                return null;
            }

            // [0] = resID, [1] = reservID, [2] = trans ID, [3] = this entity ID
            idArray = new int[MAX_ID];
            idArray[0] = Integer.parseInt(list[0]);   // to get resID
            idArray[1] = Integer.parseInt(list[1]);   // to get reservationID

            // if the resource id doesn't exist or there are more IDs
            if (GridSim.isResourceExist(idArray[0]) == false) {
                idArray = null;
            }
        }
        catch (Exception e)
        {
            idArray = null;
            System.out.println(super.get_name()
                    + ": Error - Invalid booking ID of " + bookingID);
        }

        return idArray;
    }