code: public E set(int index, E element) {
  		hashCodeUpToDate = false;
  		E oldValue = elementData(index);
  		elementData[index] = element;
  		return oldValue;
  	}
docs: Replaces the element at the specified position in this list with the
  specified element.
  
  @param index
  index of the element to replace
  @param element
  element to be stored at the specified position
  @return the element previously at the specified position
  @throws IndexOutOfBoundsException
  {@inheritDoc}