How To Sort Strings of JComboBoxes in JTables?

I have following problem:

I've inserted into the 5th column of my JTable for each row an JComboBox-Object. Everything is fine until I want to rowsort the column with setAutoCreateRowSorter(true). In this case im getting following exception:

ClassCastException: java.lang.String cannot be cast to javax.swing.JComboBox

Here are my classes that im using for my JTable:

The TableModel:

private class MyTableModel implements TableModel {

        @Override
        public void addTableModelListener(TableModelListener l) {
        }

        @Override
        public Class<?> getColumnClass(int columnIndex) {

            switch (columnIndex) {
            case 0:
                return String.class;
            case 1:
                return String.class;
            case 2:
                return String.class;
            case 3:
                return Number.class;
            case 4:
                return Boolean.class;
            case 5:
                return String.class;
            default:
                return null;
            }

        }

        @Override
        public int getColumnCount() {
            return columnNames.length;
        }

        @Override
        public String getColumnName(int columnIndex) {
            return columnNames[columnIndex];
        }

        @Override
        public int getRowCount() {
            return data[0].length - 1;
        }

        @Override
        public Object getValueAt(int rowIndex, int columnIndex) {
            return data[rowIndex][columnIndex];

        }

        @Override
        public boolean isCellEditable(int rowIndex, int columnIndex) {
            switch (columnIndex) {
            case 5:
                return true;
            default:
                return false;
            }

        }

        @Override
        public void removeTableModelListener(TableModelListener l) {
        }

        @Override
        public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
            data[rowIndex][columnIndex] = aValue;

        }

    }

The TableRenderer:

public class StringTableCellRenderer extends JLabel implements
        TableCellRenderer {

    private static final long serialVersionUID = 1L;

    public StringTableCellRenderer() {
        setOpaque(true);
        setLayout(new BorderLayout());
    }

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value,
            boolean isSelected, boolean hasFocus, int row, int column) {
        Font font = getFont().deriveFont(Font.BOLD, 15);

        if ((row % 2) == 0) {
            setBackground(new Color(240, 255, 255));
        } else {
            setBackground(new Color(191, 239, 255));
        }

        if (isSelected) {
            setBackground(new Color(0, 191, 255));
        }

        setHorizontalAlignment(JLabel.CENTER);
        setForeground(Color.BLACK);
        setFont(font);

        if (value instanceof JComboBox) {
            setText((String) ((JComboBox<?>) value).getSelectedItem());
        } else {
            setText(value.toString());
        }

        return this;
    }

}

And the TableEditor:

public class MyTableCellEditor extends AbstractCellEditor implements
        TableCellEditor, ActionListener {

    private static final long serialVersionUID = 1L;
    private String fieldValue = null;


    @Override
    public void actionPerformed(ActionEvent event) {
        if (event.getSource() instanceof JComboBox<?>) {
            JComboBox<?> jComboBox = (JComboBox<?>) event.getSource();
            fieldValue = (String) jComboBox.getSelectedItem();
        }
    }

    @Override
    public Object getCellEditorValue() {
        System.out.println("Editor: getCellEditorValue()");
        return fieldValue;
    }

    @Override
    public Component getTableCellEditorComponent(JTable table, Object value,
            boolean isSelected, int row, int column) {
        JComboBox<String> comboBox = new JComboBox<String>();
        comboBox.addItem("Me");
        comboBox.addItem("You");
        comboBox.addItem("They");
        comboBox.addItem("Us");
        comboBox.addItem("We");
        comboBox.addActionListener(this);
        System.out.println("Editor: getTableCellEditorComponent");
        if (value instanceof JComboBox<?>) {
            fieldValue = (String) ((JComboBox<?>) value).getSelectedItem();
        }

        comboBox.setSelectedItem(fieldValue);

        return comboBox;
    }

}

My idea for that problem was defining an own RowSorter-object and adding it to my JTable-Object (jTable) like this:

private class JComboBoxBoxComparator implements
            Comparator<JComboBox<String>> {

        @Override
        public int compare(JComboBox<String> o1, JComboBox<String> o2) {
            return ((String) o1.getSelectedItem()).compareTo((String) o2
                    .getSelectedItem());
        }

    }


TableRowSorter<TableModel> sorter = new TableRowSorter<TableModel>(
                jTable.getModel());
        sorter.setComparator(5, new JComboBoxBoxComparator());
        jTable.setRowSorter(sorter);

Unfortunately this does not have any effect....