In TabbedPane Diagrams do not appear

I wanted to create 2 tabs and on each tab should be four diagrams. The diagrams itself works fine on a single page, but now I need to distribute them, since they are too many. I tried the following thing, but it did not seem to work.

Code:

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public JPanel createDemoPanel() {
        JFrame demoPanel = new JFrame("TabbedPaneDemo");
                JTabbedPane tabbedPane = new JTabbedPane();
                ImageIcon icon = new ImageIcon("Month01.gif");
        JComponent panel1 = makeTextPanel("Panel #1");
        tabbedPane.addTab("Tab 1", icon, panel1,
                "Does nothing");
        tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);
        JPanel demoPanel1 = new JPanel(new GridLayout(2, 2));
                demoPanel1.add(new DemoPanelA());
                demoPanel1.add(new DemoPanelB());

        JComponent panel2 = makeTextPanel("Panel #2");
        tabbedPane.addTab("Tab 1", icon, panel2,
                "Does nothing");
        tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);
        JPanel demoPanel2 = new JPanel(new GridLayout(2, 2));
                demoPanel2.add(new DemoPanelE());
                demoPanel2.add(new DemoPanelF());
        return demoPanel1;
        }

protected JComponent makeTextPanel(String text) {
        JPanel panel = new JPanel(false);
        JLabel filler = new JLabel(text);
        filler.setHorizontalAlignment(JLabel.CENTER);
        panel.setLayout(new GridLayout(1, 1));
        panel.add(filler);
        return panel;
    }

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I do not get any error message - so it should work, but it does not? :confused: I assume something pretty fundamental is not working.
I would appreciate any hint - Thanks for your support.

This is really easy with an IDE. If you download NetBeans IDE you can drag the tabbed panel on from the Tools box, add 4 JPanels to it, and edit each panel to add your diagrams. 5 minute job?