public class ComboTest {
    public static void main(String args[]) {
        WebLookAndFeel.install();

        boolean decorateFrames = WebLookAndFeel.isDecorateFrames();
        WebLookAndFeel.setDecorateFrames(true);
        WebLookAndFeel.setDecorateDialogs(true);

        WebFrame frame = new WebFrame();
        frame.setLayout(new FlowLayout());
        frame.setPreferredSize(new Dimension(500,100));
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        final WebComboBox webComboBox = new WebComboBox();
        webComboBox.setEditable(true);
        frame.add(webComboBox);

        WebButton button = new WebButton("Add new item");
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                webComboBox.addItem("test");
            }
        });
        frame.add(button);

        frame.pack();
        frame.setLocationRelativeTo(null);

        WebLookAndFeel.setDecorateFrames(decorateFrames);
        frame.setVisible(true);
    }
}