Dynamically adding a column to a jtable - simple & urgent

Question

I am new to using JTables.
I have read the tutorial and looked at several examples, but I am still confused as to how to add/remove columns and how to add rows to the table.
I want to have a totally dynamic table which will allow me to add/remove columns and to add rows.
The table gets the data to be displayed (and the column header values) from an outside object. I thought about writing my own table model.
Here is the code for my simple table model:
import javax.swing.table.*;
import java.util.Vector;
public class MyTableModel extends AbstractTableModel{
   private Vector columnHeaders;
   private Vector data;
   // simple constructor
   public MyTableModel() {
      columnHeaders = new Vector();
      data = new Vector();  // data is a vector of vectors
   public int getColumnCount() {
      return columnHeaders.size();
   public int getRowCount() {
      if (data.size() == 0) {
          return 0;
      Vector columnData = (Vector)data.elementAt(0);
      return columnData.size();
   public Object getValueAt(int row, int column) {
      Vector columnData = (Vector)data.elementAt(column);
      return columnData.elementAt(row);
   // the method I call for dynamically adding a new empty column
   public void addNewEmptyColumn(String value) {
       columnHeaders.add(value);
       fireTableStructureChanged();
}Here is how I use the table model with my table
import javax.swing.*;
public class Demo extends JFrame{
    private JTable table;
    public Demo() {
        super("test");
        table = new JTable(new MyTableModel());
        getContentPane().add(table);
        pack();
        show();
    public void addColumn(String value) {
        MyTableModel model = (MyTableModel)table.getModel();
        model.addNewEmptyColumn(value);
    public static void main(String[] args) {
        Demo demo = new Demo();
        // here I am trying to add columns...
        demo.addColumn("one");
        demo.addColumn("two");
}I try to add columns, but nothing happens!!!
What am I doing wrong?
I would appreciate if someone who take himself/herslef to be a JTable expert could give me his/her e-mail and this way I won't bother the rest of the world with my stupid JTable questions...
Sincerely
Nir

Answer 1

I have another question.
What if I want to render the table headers in a certain way.
I would like to use:
TableColumn's setHeaderRenderer(TableCellRenderer headerRenderer).
But in order to do it, I need to get a TableColumn.
How do I get it from the model?
I thought about subclassing JTable and overriding:
public void tableChanged(TableModelEvent e)that function is called everytime I invoke fireTableStructureChanged().
In that function, I am assuming that a column has been added, however, when I query for JTable's getColumnCount(), I keep getting 0!