*/
@GwtIncompatible
public final class SafeTreeSet<E> implements Serializable, NavigableSet<E> {
  @SuppressWarnings("unchecked")
  private static final Comparator<Object> NATURAL_ORDER =
      new Comparator<Object>() {
        @Override
        public int compare(Object o1, Object o2) {
          return ((Comparable<Object>) o1).compareTo(o2);
        }
      };

  private final NavigableSet<E> delegate;

  public SafeTreeSet() {

   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be
   *     {@code null}) and returns {@code Optional.empty()} if it has none.
   */
  @SuppressWarnings("unchecked")
  public static <T> Collector<T, ?, Optional<T>> toOptional() {
    return (Collector) TO_OPTIONAL;
  }

  private static final Object NULL_PLACEHOLDER = new Object();

      default:
        @SuppressWarnings("unchecked")
        List<E> castedList = (List<E>) list;
        return new RegularImmutableList<E>(castedList);
    }
  }

  /**
   * Views the array as an immutable list. The array must have only {@code E} elements.
   *
   * <p>The array must be internally created.
   */
  @SuppressWarnings("unchecked") // caller is reponsible for getting this right

    this.forwardOrder = checkNotNull(forwardOrder);
  }

  @Override
  public int compare(@ParametricNullness T a, @ParametricNullness T b) {
    return forwardOrder.compare(b, a);
  }

  @SuppressWarnings("unchecked") // how to explain?
  @Override
  public <S extends T> Ordering<S> reverse() {
    return (Ordering<S>) forwardOrder;
  }

  // Override the min/max methods to "hoist" delegation outside loops

  @Override

   *   <li>To treat {@link InterruptedException} uniformly with other exceptions, use {@link
   *       Futures#getChecked(Future, Class) Futures.getChecked}.
   *   <li>To get uninterruptibility and remove checked exceptions, use {@link
   *       Futures#getUnchecked}.
   * </ul>
   *
   * @throws ExecutionException if the computation threw an exception
   * @throws CancellationException if the computation was cancelled

  // hasNext/next), but we'll cop out for now, knowing that
  // next() both start by invoking hasNext() anyway.

  /** Throws an undeclared checked exception. */
  private static void sneakyThrow(Throwable t) {
    class SneakyThrower<T extends Throwable> {
      @SuppressWarnings("unchecked") // intentionally unsafe for test
      void throwIt(Throwable t) throws T {
        throw (T) t;
      }
    }

  /**
   * Returns an empty {@code ImmutableClassToInstanceMap}.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   *
   * @since 19.0
   */
  @SuppressWarnings("unchecked")
  public static <B> ImmutableClassToInstanceMap<B> of() {
    return (ImmutableClassToInstanceMap<B>) EMPTY;
  }

  /**
   * Returns an {@code ImmutableClassToInstanceMap} containing a single entry.
   *

                CollectionFeature.ALLOWS_NULL_VALUES,
                CollectionFeature.GENERAL_PURPOSE)
            .createTestSuite());

    return suite;
  }

  @SuppressWarnings({"rawtypes", "unchecked"})
  public void testForwarding() {
    new ForwardingWrapperTester()
        .testForwarding(
            Queue.class,
            new Function<Queue, Queue>() {
              @Override

      } catch (Exception e) { // sneaky checked exception
        if (exception == null) {
          exception = e;
        } else {
          exception.addSuppressed(e);
        }
      }
    }
    if (exception != null) {
      // Normally this is a RuntimeException that doesn't need sneakyThrow.
      // But theoretically we could see sneaky checked exception
      sneakyThrow(exception);
    }
  }

   * @since 7.0
   */
  @Override
  protected boolean standardContains(@CheckForNull Object object) {
    try {
      // any ClassCastExceptions and NullPointerExceptions are caught
      @SuppressWarnings({"unchecked", "nullness"})
      SortedSet<@Nullable Object> self = (SortedSet<@Nullable Object>) this;
      Object ceiling = self.tailSet(object).first();
      return unsafeCompare(comparator(), ceiling, object) == 0;