jButton de Atualizar numa Jtable consulta

public PDV() {
        super();

        String url = "jdbc:mysql://localhost:3307/sistemacomercial";
        String usuario = "root";
        String senha = "123456";
        try {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            con = DriverManager.getConnection(url, usuario, senha);
        } catch (Exception e) {
            JOptionPane.showMessageDialog(null, "Conexão não estabelecida", "Mensagem do Programa",
                    JOptionPane.ERROR_MESSAGE);
        }

        buscaTabela();
        btnAtualizar.addActionListener(new Atualizar());
    }

    public class Atualizar implements ActionListener {
        public void actionPerformed(ActionEvent clic) {

            Statement st;
            ResultSet res;

            try {

                Vector cabecalho = new Vector();
                Vector linhas = new Vector();
                st = con.createStatement();
                res = st.executeQuery("SELECT * FROM PDV ORDER BY Data");
                res.next();
                ResultSetMetaData rsmd = res.getMetaData();
                for (int i = 1; i <= rsmd.getColumnCount(); ++i) {
                    cabecalho.addElement(rsmd.getColumnName(i));
                }
                do {
                    linhas.addElement(proximaLinha(res, rsmd));
                } while (res.next());

                tabela = new JTable(linhas, cabecalho);
                tabela.setSize(new Dimension(693, 190));
                tabela.getColumnModel();
                tabela.setFont(new Font("Lucida Sans", Font.CENTER_BASELINE, 14));
                tabela.setRowHeight(20);
                tabela.updateUI();
                tabela.getColumnModel().getColumn(1).setPreferredWidth(300);
                JScrollPane scroller = new JScrollPane(tabela);
                scroller.setBorder(BorderFactory.createLineBorder(Color.black, 5));
                scroller.setBounds(new Rectangle(-1, 190, 676, 289));
                scroller.updateUI();

                getJContentPane().add(scroller, BorderLayout.CENTER);

                st.close();

            } catch (SQLException sqlex) {
            }
            return null;
        }

        private Vector proximaLinha(ResultSet rs, ResultSetMetaData rsmd) {
            Vector LinhaAtual = new Vector();
            try {
                for (int i = 1; i <= rsmd.getColumnCount(); ++i) {
                    switch (rsmd.getColumnType(i)) {
                        case Types.VARCHAR:
                            LinhaAtual.addElement(rs.getString(i));
                            break;
                        case Types.TIMESTAMP:
                            LinhaAtual.addElement(rs.getDate(i));
                            break;
                        case Types.DOUBLE:
                            LinhaAtual.addElement(new Double(rs.getDouble(i)));
                            break;
                        case Types.INTEGER:
                            LinhaAtual.addElement(new Double(rs.getDouble(i)));
                            break;
                    }
                }
            } catch (SQLException e) {
            }
            return LinhaAtual;
        }
    }