modCount++;
    size--;
    if (size == index) {
      queue[size] = null;
      return null;
    }
    E actualLastElement = elementData(size);
    int lastElementAt = heapForIndex(size).swapWithConceptuallyLastElement(actualLastElement);
    if (lastElementAt == index) {
      // 'actualLastElement' is now at 'lastElementAt', and the element that was at 'lastElementAt'