code: public E set(int index, E element) {
          if (index >= size)
              throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
  
          E oldValue = (E) 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}