public static <T> Set<T> asUnmodifiabledOrderedSet(final T item) {
        return item != null
                ? Collections.singleton(item)
                : Collections.emptySet();
    }
Return a {@link Set} containing items, with iteration order matching
the order in items array. Useful in config classes where a HashSet would
result in an undefined order on serialisation.
stroom-util/src/main/java/stroom/util/collections/CollectionUtil.java