private boolean onlyJarsSelected() {
    for (PackagingSourceItem item : mySourceItemsTree.getSelectedItems()) {
      if (item.isProvideElements() && (!item.getKindOfProducedElements().containsJarFiles() || item.getKindOfProducedElements().containsDirectoriesWithClasses())) {
        return false;
      }
    }
    return true;
  }
private boolean onlyJarsSelected()