static class CombinedMap<A, B> extends AbstractMap<A, B> {

  new L<Map<A, B>> maps;

  *() {}

  *(Map<A, B>... maps) { addAllNonNulls(this.maps, maps); }

  <C extends Map<A, B>> *(Collection<C> maps) { addAllNonNulls(this.maps, maps); }

  public int size() { ret lengthLevel2_maps(maps); }

  public Set<Map.Entry<A, B>> entrySet() { fail(); }

  public bool containsKey(O o) {

    for (Map<A, B> map : maps)

      if (map.containsKey(o))

        true;

    false;

  }

  @Override

  public B get(O o) {

    for (Map<A, B> map : maps)

      if (map.containsKey(o))

        ret map.get(o);

    null;

  }

}