Not showing radio button group inside column in jtable

I am trying to add radio button group similar to http://www.java2s.com/Code/Java/Swing-Components/RadioButtonTableExample2.htm

In my form, I followed the the above tutorial but I am using AbstractTableModel instead of DefaultTableModel.

Here is my code, it does not show anything on column no errors:

StudentTableModel model = new StudentTableModel(studentList);

    // JScrollPane scrollPane = new JScrollPane(table);
    final JScrollPane scrollPane = new JScrollPane(
            table,
            JScrollPane.VERTICAL_SCROLLBAR_NEVER,
            JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
    Dimension d = table.getPreferredSize();
    scrollPane.setPreferredSize(
            new Dimension(d.width,table.getRowHeight()*rows));

    // code for radio buttons
    String[] answer = { "A", "B", "C" };
    TableColumnModel columnModel = table.getColumnModel();

    for (int tc = 7; tc < table.getColumnCount(); tc++)
    {
    columnModel.getColumn(tc).setCellRenderer(
            new MainClass().new RadioButtonRenderer(answer));
    columnModel.getColumn(tc).setCellEditor(
            new MainClass().new RadioButtonEditor(new JCheckBox(),  new MainClass().new RadioButtonPanel(
                    answer)));
    }
    table.setModel(model);

    frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
    frame.getContentPane().add(navigation, BorderLayout.SOUTH);
    frame.pack();

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);

Thanks in advance

The code is trying to set renderer and editor before setting the model. So there are no columns to set a renderer/editor on. The model must be set first, only then the columns will be created - just creating the model does not link it to the table, the table does not know beforehand how many columns it will have.

Probably you want something like

StudentTableModel model = new StudentTableModel(studentList);
table.setModel(model);    // moved from below

// JScrollPane scrollPane = new JScrollPane(table);
...

The example you are following is doing so, actually it creates the table with the model as argument...

Hint: why new MainClass() in new MainClass().new RadioButtonRenderer(... and others? You really want a new MainClass? Declare these classes as static and remove the new MainClass()