static <A, B> void multiMapPut(Map<A, L<B>> map, A a, B b) {
  L<B> l = map.get(a);
  if (l == null)
    map.put(a, l = new L);
  l.add(b);
}

ifclass MultiMap
static <A, B> void multiMapPut(MultiMap<A, B> mm, A key, B value) {
  if (mm != null && key != null && value != null) mm.put(key, value);
}
endif