Tablesorter and filtering data in a table

public class Frame extends javax.swing.JFrame {

    Connection conn = null;  
    
    ResultSet rs = null;
        
    PreparedStatement pst = null;
        
    public void updateTable(){
    
        String sql = "select * from employee";
        
        try{
        pst = conn.prepareStatement(sql);
        
        rs = pst.executeQuery();
        
        table.setModel(DbUtils.resultSetToTableModel(rs));
        }catch(Exception e){
        JOptionPane.showMessageDialog(rootPane, e);
        }
    }
   
    public void sortTable(){
        
        MyTableModel tableModel ;
        
        TableRowSorter<mytablemodel> sorter;
        
        tableModel = new MyTableModel();
        
        sorter = new TableRowSorter<mytablemodel>(tableModel);
        
        table.setModel(tableModel);
        
        table.setRowSorter(sorter);
        
        txtFilter.getDocument().addDocumentListener(new DocumentListener() {

            @Override
            public void insertUpdate(DocumentEvent e) {
                filterTable();
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                filterTable();
            }

            @Override
            public void changedUpdate(DocumentEvent e) {
              filterTable();  
            }
        });
    }
    public void filterTable(){
         MyTableModel tableModel = new MyTableModel();
        
        TableRowSorter<mytablemodel> sorter = new TableRowSorter<mytablemodel>(tableModel);
            
      RowFilter<mytablemodel,> rf = null;
    //If current expression doesn't parse, don't update.
    try {
        rf = RowFilter.regexFilter(txtFilter.getText());
        
    } catch (java.util.regex.PatternSyntaxException e) {
        return;
    }
    sorter.setRowFilter(rf);
      
    }
    private void formWindowOpened(java.awt.event.WindowEvent evt) {                                  
        // TODO add your handling code here:
        
        conn = connect.connectDb();
        
         updateTable();
        
         sortTable();
         
         filterTable();
    }                                 

     
     
    private void txtFilterKeyReleased(java.awt.event.KeyEvent evt) {                                      
      
    }                                     
  
  
    /**
     * @param args the command line arguments
     */
   
    public static void main(String args[]) {
       
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new Frame().setVisible(true);
            }
        });
    }
}