static <A> ArrayList<A> cloneList(Iterable<A> l) {
  ret l instanceof Collection ? cloneList((Collection) l) : asList(l);
}

static <A> ArrayList<A> cloneList(Collection<A> l) {
  if (l == null) ret new L;
  synchronized(collectionMutex(l)) {
    ret new ArrayList<A>(l);
  }
}