public Object getValueAt(int row, int col) {
            switch(col){
                case 0: return row+1;
                case 1: return data.get(row).getNbr().getId();
                case 2: return data.get(row).getNbr().getAddr().getHostAddress();
                case 3: return data.get(row).getCost();
            }
            return null;
        }