if (comboBox.getRenderer() instanceof UIResource)
  protected void uninstallComponents()  {    // uninstall arrow button    unconfigureArrowButton();    comboBox.remove(arrowButton);    arrowButton = null;    listBox = null;    popup = null;    comboBox.setRenderer(null);    // if the editor is not an instanceof UIResource, it was not set by the    // UI delegate, so don't clear it...    ComboBoxEditor currentEditor = comboBox.getEditor();    if (currentEditor instanceof UIResource)      {    comboBox.setEditor(null);    editor = null;  }  }