static <A> bool allElementsEqual(Iterable<A> l) {
  if (l == null) true;
  Iterator<A> it = iterator(l);
  if (!it.hasNext()) true;
  A a = it.next();
  while ping (it.hasNext()) {
    if (!eq(a, it.next())) false;
  }
  true;
}

Began life as a copy of #1008440