Horizontal scrollbar for JComboBox - Not workable under Mac

Question

By referring to this thread Re: Horizontal scrollbar for JComboBox across multiple look and feel I try to provide horizontal scroll bar for JComboBox to my clients.
private void adjustScrollBar() {
    //if (this.getItemCount() == 0) return;
    Object comp = this.getUI().getAccessibleChild(this, 0);
    if (!(comp instanceof JPopupMenu)) {
        return;
    JPopupMenu popup = (JPopupMenu) comp;
    // Works fine under Windows and Ubuntu Linux
    // However, in OSX 10.6.4
    // javax.swing.Box$Filler cannot be cast to javax.swing.JScrollPane
    JScrollPane scrollPane = (JScrollPane) popup.getComponent(0);
    scrollPane.setHorizontalScrollBar(new JScrollBar(JScrollBar.HORIZONTAL));
    scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
}The above code will cause ClassException under OSX 10.6.4. (Works fine for Windows and Linux)
Any suggestion to resolve this problem. Sorry. I do not have a Mac machine. Hence, can't experiment out much with it.
Thanks

Answer 1

The following code works quite well for me.
    private void adjustScrollBar() {
        final int max_search = 8;
        // i < max_search is just a safe guard when getAccessibleChildrenCount
        // returns an arbitary large number. 8 is magic number
        JPopupMenu popup = null;
        for (int i = 0, count = this.getUI().getAccessibleChildrenCount(this); i < count && i < max_search; i++) {
            Object o = this.getUI().getAccessibleChild(this, i);
            if (o instanceof JPopupMenu) {
                popup = (JPopupMenu)o;
                break;
        if (popup == null) {
            return;
        JScrollPane scrollPane = null;
        for (int i = 0, count = popup.getComponentCount(); i < count && i < max_search; i++) {
            Component c = popup.getComponent(i);
            if (c instanceof JScrollPane) {
                scrollPane = (JScrollPane)c;
                break;
        if (scrollPane == null) {
            return;
        scrollPane.setHorizontalScrollBar(new JScrollBar(JScrollBar.HORIZONTAL));
        scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    }