code: @Override 
  	public void insertElementAt(E obj, int index) {
  		int idx = getRealIndex(index);
  		super.insertElementAt(obj, idx);
  	}
docs: Inserts the specified object as a component in this vector at the specified index.
  
  @param obj
  the element to insert.
  @param index
  the index at which the element should be inserted; it 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#insertElementAt(java.lang.Object, int)