code: private static Set<String> setFor( String... elements ) {
          Set<String> set = new HashSet<String>(elements.length);
          set.addAll(Arrays.asList(elements));
  
          return set;
      }
docs: Returns an unmodifiable set containing the elements passed in to this method
  
  @param elements a set of elements; may not be null
  @return an unmodifiable set containing all of the elements in {@code elements}; never null