code: @Nonnull
    public static <ELEMENTTYPE> Iterator <ELEMENTTYPE> getCombinedIterator (@Nullable final Iterator <? extends ELEMENTTYPE> aIter1,
                                                                            @Nullable final Iterator <? extends ELEMENTTYPE> aIter2)
    {
      return new CombinedIterator <> (aIter1, aIter2);
    }
docs: Get a merged iterator of both iterators. The first iterator is iterated
  first, the second one afterwards.
  
  @param <ELEMENTTYPE>
  The type of elements to be enumerated.
  @param aIter1
  First iterator. May be <code>null</code>.
  @param aIter2
  Second iterator. May be <code>null</code>.
  @return The merged iterator. Never <code>null</code>.