code: @Override
  	public void add(int index, E element) {
  		int idx = getRealIndex(index);
  		super.add(idx, element);
  	}
docs: Inserts the specified element at the specified position in this Vector.
  
  @param index
  the index can be a positive number, or a negative number that is smaller
  than the size of the vector; see {@link #getRealIndex(int)}.
  @see java.util.Vector#add(int, java.lang.Object)