public static <S> Iterator<S> concat(final Iterator<S>... iterators) {
        final MultiIterator<S> iterator = new MultiIterator<>();
        for (final Iterator<S> itty : iterators) {
            iterator.addIterator(itty);
        }
        return iterator;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/util/iterator/IteratorUtils.java