public MainFrame() {
        extractorFactory = new ExtractorFactory();
        initComponents();
        jTree = new JTree();
        jTree.setModel(null);        
        if (menuOpenIconPath != null && menuOpenIconPath != null
                && extractIconPath != null) {
           ImageIcon menuOpenIcon = new ImageIcon(this.getClass().getResource(menuOpenIconPath));
           ImageIcon menuCloseIcon = new ImageIcon(this.getClass().getResource(menuCloseIconPath));
           ImageIcon extractToolIcon = new ImageIcon(this.getClass().getResource(extractIconPath));
           ImageIcon extractItemIcon = new ImageIcon(this.getClass().getResource(extractIconPath));
           ImageIcon aboutItemIcon = new ImageIcon(this.getClass().getResource(aboutIconPath));
           ImageIcon readyStatusIcon = new ImageIcon(this.getClass().getResource(readyStatusIconPath));
           openItem.setIcon(menuOpenIcon);
           closeItem.setIcon(menuCloseIcon);
           openToolButton.setIcon(menuOpenIcon);
           extractToolButton.setIcon(extractToolIcon);
           extractItem.setIcon(extractItemIcon);
           aboutItem.setIcon(aboutItemIcon);
           statusIconLabel.setIcon(readyStatusIcon);
        }
        contentList = new JList();
        jScrollPane1.setViewportView(jTree);
    }