code: static public Enumeration<?> sortKeys(Set<String> keySet) {
          List<String> sortedList = new ArrayList<>();
          sortedList.addAll(keySet);
          Collections.sort(sortedList);
          return Collections.enumeration(sortedList);
      }
docs: To be compatible with version control systems, we need to sort properties
  before storing them to disk. Otherwise each change may lead to problems
  by diff against previous version - because Property entries are randomly
  distributed (it's a map).
  
  @param keySet
  non null set instance to sort
  @return non null list which contains all given keys, sorted
  lexicographically. The list may be empty if given set was empty