/**
  * Swaps the elements at the specified positions in the specified list.
  * (If the specified positions are equal, invoking this method leaves the list unchanged.)
   *
   * @param list the list in which to swap elements.
   * @param i the index of one element to be swapped.
   * @param the index of the other element to be swapped.
   * @throws IndexOutOfBoundsException if either i or j is out of range.
 */