code: public final void addSubEntries(final Collection<NavigationEntryInterface> psubEntries) {
      if (!CollectionUtils.isEmpty(psubEntries)) {
        subEntries.addAll(psubEntries);
        subEntries.forEach(subEntry -> subEntry.setParentEntry(this));
      }
    }
docs: add a menu sub entries.
  
  @param psubEntries the sub entries to add