*
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#sets">{@code Sets}</a>.
 *
 * @author Kevin Bourrillion
 * @author Jared Levy
 * @author Chris Povirk
 * @since 2.0
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class Sets {
  private Sets() {}

  /**

              /*
               * requireNonNull is safe because we've initialized these if
               * !GENERATE_CANCELLATION_CAUSES.
               *
               * TODO(cpovirk): Maybe it would be cleaner to define a CancellationSupplier interface
               * with two implementations, one that contains causeless Cancellation instances and

      @Override
      protected Iterator<Integer> newTargetIterator() {
        return Iterators.forArray(1, 2, 3);
      }
    }.test();
  }

  /*
   * TODO(cpovirk): Test forArray with ListIteratorTester (not just IteratorTester), including with
   * a start position other than 0.
   */

  public void testForEnumerationEmpty() {
    Enumeration<Integer> enumer = enumerate();