Cannot enter symbols other than numbers into cell

Question

I'm using a JTable with custom TableModel. All editable cells accept numbers (0..9), but does not accept any other symbols (letters, special symbols such as "," or "." etc).
I'm sure the solution to let my JTable accept other symbols ist very simple, but I just cant find which component or class controlls this!
There ist no data type validation in my TableModel:
    public void setValueAt(Object value, int row, int col) {
            data[row][col] = value;
            fireTableCellUpdated(row, col);
        }

Answer 1

No I didn't!
I'm using this code to do a "doClick()" on a JTable cell when component with the table is shown to enter editing mode.
But when I double click on a cell, there must be other (standard???) editor being evoked to edit the cell, right?
            if(AddedArticlesTable.getRowCount() != 0){
                SwingUtilities.invokeLater( new Runnable() {
                     public void run() {
                         AddedArticlesTable.editCellAt(
                                 AddedArticlesTable.getRowCount() - 1, 0);
                         // replace row and col with desire row and col
                         JTextField editor = (JTextField)(
                         (DefaultCellEditor)AddedArticlesTable.getCellEditor(
                            AddedArticlesTable.getRowCount() - 1, 0)
                            ).getComponent();
                         // replace row and col with desire row and col
                         editor.selectAll();
                         editor.requestFocusInWindow();
            }