Atualização de um JTbalbe

private void showDatabaseTable() {
        try {
            try {
                url = "jdbc:odbc:CollegeMySQL";
                Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                connection = DriverManager.getConnection(url);
            }
            catch(ClassNotFoundException cnfx) {
                cnfx.printStackTrace();
                JOptionPane.showMessageDialog(null,"O Sistema não obteve acesso ao Banco de Dados");
            }
            catch (SQLException sqlx) {
                sqlx.printStackTrace();
                JOptionPane.showMessageDialog(null,"O Sistema não obteve acesso ao Banco de Dados");
            }
            catch (Exception ex) {
                ex.printStackTrace();
                JOptionPane.showMessageDialog(null,"O Sistema não obteve acesso ao Banco de Dados");
            }
            Connection conexao = DriverManager.getConnection(url);
            Statement st  = conexao.createStatement();
            ResultSet rec = st.executeQuery(
            "SELECT codigo, descricao, unidade FROM Unidades ");
            displayDatabaseRecords(rec);
            st.close();
        }
        catch (SQLException sqlx) {
            sqlx.printStackTrace();
        }
}
    
private void displayDatabaseRecords(ResultSet rS)  throws SQLException {
        boolean moreRecords = rS.next();
        if (!moreRecords) {
        }
        try {
            ResultSetMetaData rs = rS.getMetaData();
            for (int i = 1; i <= rs.getColumnCount(); ++i)
                gridColumns.addElement(rs.getColumnName(i));
            do {
                gridRows.addElement(getNextRow(rS,rs));
            } while (rS.next());
            jTable1 = new JTable(gridRows, gridColumns) {
                public Component prepareRenderer(TableCellRenderer renderer,
                int rowIndex, int vColIndex) {
                    Component c = super.prepareRenderer(renderer, rowIndex, vColIndex);
                    if (rowIndex % 2 == 0 && !isCellSelected(rowIndex, vColIndex)) {
                        c.setBackground(Color.orange);
                    } else {
                        c.setBackground(getBackground());
                    }
                    return c;
                }
            };    
            int vColIndex = 0;
            jTable1.getColumnModel().getColumn(vColIndex).setHeaderValue("CODIGO");
            jTable1.getColumnModel().getColumn(vColIndex).setMaxWidth(80);
            vColIndex = 1;
            jTable1.getColumnModel().getColumn(vColIndex).setHeaderValue("DESCRIÇÃO");
            vColIndex = 2;
            jTable1.getColumnModel().getColumn(vColIndex).setHeaderValue("UNIDADE");
            jTable1.setOpaque(true);
            jTable1.setBackground(new java.awt.Color(255, 255, 255));
            JScrollPane scroller = new JScrollPane(jTable1);
            scroller.setBackground(new java.awt.Color(255, 255, 255));
            scroller.setOpaque(true);
            jPanel1.setBackground(new java.awt.Color(255, 255, 255));
            jPanel1.setOpaque(true);
            jTable1.setRowHeight(20);
            jTable1.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
            jTable1.setRowSelectionAllowed(true);
            jPanel1.add(scroller);
            scroller.revalidate();
            validate();
        }
        catch(SQLException sqlx) {
            sqlx.printStackTrace();
        }
}
    
private Vector getNextRow(ResultSet rS, ResultSetMetaData rs) throws SQLException {
        Vector currentRow = new Vector();
        for (int i = 1; i <= rs.getColumnCount(); ++i)
            if (rs.getColumnType(i) == Types.VARCHAR) {
                currentRow.addElement(rS.getString(i));
            }
            else {
                //
            }
        return currentRow;
}