}

  public void testSkip_structurallyModifiedSkipSome() throws Exception {
    Collection<String> set = new LinkedHashSet<>(asList("a", "b", "c"));
    Iterable<String> tail = skip(set, 1);
    set.remove("b");
    set.addAll(newArrayList("A", "B", "C"));
    assertThat(tail).containsExactly("c", "A", "B", "C").inOrder();
  }

  }

  @SuppressWarnings("nullness") // test of a bogus call
  public void testNullTimeUnit() throws Exception {
    future.set(1);
    assertThrows(NullPointerException.class, () -> future.get(0, null));
  }

  public void testNegativeTimeout() throws Exception {
    future.set(1);
    assertEquals(1, future.get(-1, SECONDS).intValue());
  }

  @J2ktIncompatible
  @GwtIncompatible // threads

  }

  @SuppressWarnings("nullness") // test of a bogus call
  public void testNullTimeUnit() throws Exception {
    future.set(1);
    assertThrows(NullPointerException.class, () -> future.get(0, null));
  }

  public void testNegativeTimeout() throws Exception {
    future.set(1);
    assertEquals(1, future.get(-1, SECONDS).intValue());
  }

  @J2ktIncompatible
  @GwtIncompatible // threads

                exitCode.set(1);
                latch.countDown();
            });

            try {
                latch.await();
            } catch (final InterruptedException ignore) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Interrupted.", ignore);
                }
                exitCode.set(1);
            }
        }

    assertThat(list.set(0, true)).isFalse();
    assertThat(list.set(0, false)).isTrue();
    assertThrows(NullPointerException.class, () -> list.set(0, null));
    assertThrows(IndexOutOfBoundsException.class, () -> list.set(1, true));
  }

  public void testAsListCanonicalValues() {
    List<Boolean> list = Booleans.asList(true, false);
    assertThat(list.get(0)).isSameInstanceAs(true);

    secondSignal.await();

    // start waiting thread
    new Thread() {
      @Override
      public void run() {
        thirdSignal.countDown();
        result.set(1, cache.getUnchecked(key));
        doneSignal.countDown();
      }
    }.start();

    // give the second get a chance to run; it is okay for this to be racy

    secondSignal.await();

    // start waiting thread
    new Thread() {
      @Override
      public void run() {
        thirdSignal.countDown();
        result.set(1, cache.getUnchecked(key));
        doneSignal.countDown();
      }
    }.start();

    // give the second get a chance to run; it is okay for this to be racy

   *
   * <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
   * equivalence relations, for example if {@code set1} is a {@link HashSet} and {@code set2} is a
   * {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> difference(Set<E> set1, Set<?> set2) {
    checkNotNull(set1, "set1");

   */
  public static <E extends @Nullable Object> SetView<E> union(
      Set<? extends E> set1, Set<? extends E> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {
      @Override
      public int size() {
        int size = set1.size();
        for (E e : set2) {
          if (!set1.contains(e)) {
            size++;
          }
        }
        return size;

    BiPredicate<ImmutableSet<TypeWithDuplicates>, ImmutableSet<TypeWithDuplicates>> equivalence =
        (set1, set2) -> {
          if (!set1.equals(set2)) {
            return false;
          }
          for (int i = 0; i < set1.size(); i++) {
            if (!set1.asList().get(i).fullEquals(set2.asList().get(i))) {
              return false;
            }
          }
          return true;