Thowing to many errors

[ben riches]

Hi All,
When I run this code and I select a table with an 0 at the beggining it thows a Exception which is fine but when I click into the comboBox where I selected the table it thows the exception again.
Why does it thow the Exception twice and is there a way where I can have it thown only once.
Also is there a way where you can have a diffrent JOption pane (error message) pop up for every diffrent Exception that is thown?

import javax.swing.*;
import javax.swing.table.*;
import java.awt.event.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*;
public class ComboBoxTable{ 
static Connection conn2;
   static DatabaseMetaData DMD;
   static JComboBox group = new JComboBox();
   static JComboBox groupList = new JComboBox();
  public static void main(String[] args) {
 
try  { 

     // Load the database driver
   Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" ) ;
    conn2 = DriverManager.getConnection( "jdbc :-o	 dbc:myProject") ;
   DMD=conn2 .getMetaData();
   ResultSet rs=DMD.getTables(null,null,null,new String[]{"TABLE"});
   while(rs.next()) {

group.addItem((String)rs.getString(3));

   }
   rs.close() ;

 } catch (SQLException se ) {
   System.out.println( "SQL Exception: " + se ) ;
 } catch (Exception e ) {
   System.out.println( e ) ;
 }

group.addActionListener(new ActionListener()  {
   public void actionPerformed(ActionEvent e)  {
String tbl = (String)group.getSelectedItem();
 try {
      Statement st=conn2.createStatement();
    st.execute("SELECT * FROM "+tbl+" WHERE 1=0");
    ResultSet rs=st.getResultSet();
    ResultSetMetaData md=rs.getMetaData();
    groupList.removeAllItems();
   for (int i=1;i<=md.getColumnCount();i++) {
groupList.addItem(md.getColumnName(i));
    }
   st.close() ;
 } catch (SQLException se ) {
   System.out.println( "SQL Exception: " + se ) ;
 } catch (Exception ex ) {
   System.out.println( ex ) ;
 }
      }
});
int j=10;
      String[][] data = new String[j][2];
      for (int k=0; k<j; k++){
         String[] row = {"",""};
         data[k] = row;
      }
   
    String[] colNames = {"Column A", "Column B"};
    JTextField jtf = new JTextField();
    JTable tbl = new JTable(data, colNames);
// Create the combo box editor
    DefaultCellEditor editor = new DefaultCellEditor(groupList);
// ADDED IN MY ATTEMPT TO HAVE TO COLUMNS WITH COMBOBOXES
    DefaultCellEditor editor2 = new DefaultCellEditor(group);
// Assign the editor to the second column
    TableColumnModel tcm = tbl.getColumnModel();
    tcm.getColumn(0).setCellEditor(editor2);
 // ADDED
    tcm.getColumn(1).setCellEditor(editor);
// Set column widths
    tcm.getColumn(0).setPreferredWidth(200);
    tcm.getColumn(1).setPreferredWidth(100);
// Set row heighht
    tbl.setRowHeight(20);
    tbl.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
    tbl.setPreferredScrollableViewportSize(tbl.getPreferredSize());
JFrame f = new JFrame("ComboBoxDemo");
    f.getContentPane().add(new JScrollPane(tbl), "Center");
   
    f.pack();
    f.addWindowListener(new WindowAdapter() {


      public void windowClosing(WindowEvent evt) {
         System.exit(0);
      }
    });
    f.setVisible(true);
  }
}

Thanks
ben