code: private void fastRemove(int index) {
          modCount++;
          int numMoved = size - index - 1;
          if (numMoved > 0)
              System.arraycopy(elementData, index+1, elementData, index,
                               numMoved);
          elementData[--size] = null; // clear to let GC do its work
      }
docs: /*
  Private remove method that skips bounds checking and does not
  return the value removed.