code: public static <T> Set<T> symmetricDifference(Set<T> setA, Set<T> setB) {
          Set<T> union = union(setA, setB);
          Set<T> intersection = intersection(setA, setB);
          return difference(union, intersection);
      }
docs: This method finds the symmetric difference between set A and set B i.e. which items does not exist in either
  set A or set B. This is the opposite of the intersect of set A and set B.
  @param setA set A
  @param setB set B
  @param <T> type
  @return a new set containing the symmetric difference