// inner list can be a normal ArrayList
static <A> NotifyingList<A> notifyingList(L innerList, Runnable onChange) {
  ret new NotifyingList<A>(innerList) {
    void change() { onChange.run(); }
  };
}

static <A> NotifyingList<A> notifyingList(Runnable onChange) {
  ret listWithNotify(onChange);
}