code: private void heapifyUp(Entry<E> entry) {
      while (true) {
        if (entry.index == 0) {
          break;
        }
        Entry<E> parentEntry = parent(entry);
        if (compare(entry, parentEntry) <= 0) {
          break;
        }
        swap(entry, parentEntry);
      }
    }
docs: iterative heapify up: move item o at index up until correctly placed