private void configureGuiToolkit() {
        String operatingSystem = System.getProperty("os.name").toLowerCase();
        boolean isUnix = operatingSystem.contains("nix")
                || operatingSystem.contains("nux")
                || operatingSystem.contains("aix");

        try {
            if (isUnix) {
                UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
            } else {
                UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            }
        } catch (UnsupportedLookAndFeelException | ClassNotFoundException | IllegalAccessException | InstantiationException ex) {
            throw new IllegalStateException("The Look&Feel could not be configured correctly: " + ex.getMessage());
        }
    }