if (header.getResizingColumn() == null)
    public void propertyChange(PropertyChangeEvent ev)    {      if (ev.getPropertyName().equals("preferredWidth"))        {          JTableHeader header = getTableHeader();	  if (header != null)	    {          TableColumn col = (TableColumn) ev.getSource();          header.setResizingColumn(col);          doLayout();          header.setResizingColumn(null);        }    }  }