protected List<ContentEntry> addContentEntries(final VirtualFile[] files) {
    List<ContentEntry> contentEntries = new ArrayList<>();
    for (final VirtualFile file : files) {
      if (isAlreadyAdded(file)) {
        continue;
      }
      final ContentEntry contentEntry = getModel().addContentEntry(file);
      contentEntries.add(contentEntry);
    }
    return contentEntries;
  }
protected List<ContentEntry> addContentEntries(final VirtualFile[] files)