*
   *   private static final class FooFactoryForTest {
   *     public static Foo create(String a, String b, int c, boolean d) {
   *       return Foo.builder()
   *           .setA(a)
   *           .setB(b)
   *           .setC(c)
   *           .setD(d)
   *           .build();
   *     }
   *   }
   *
   *   public void testEquals() {
   *     new ClassSanityTester()

   *
   *   private static final class FooFactoryForTest {
   *     public static Foo create(String a, String b, int c, boolean d) {
   *       return Foo.builder()
   *           .setA(a)
   *           .setB(b)
   *           .setC(c)
   *           .setD(d)
   *           .build();
   *     }
   *   }
   *
   *   public void testEquals() {
   *     new ClassSanityTester()

   *
   * <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");
    checkNotNull(set2, "set2");

    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "b", "f"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("z"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("b", "d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("f", "d", "a"))));
  }

    Set<Integer> set2 = newHashSet(2, 3);
    Set<Integer> difference = difference(set1, set2);
    assertThat(difference).containsExactly(1);
    set1.add(0);
    assertThat(difference).containsExactly(0, 1);
    set2.remove(2);
    assertThat(difference).containsExactly(0, 1, 2);
  }

  public void testSymmetricDifference_isView() {
    Set<Integer> set1 = newHashSet(1, 2);
    Set<Integer> set2 = newHashSet(2, 3);

  }

  /**
   * Construct a new {@link java.util.Set} that is the intersection of the given sets.
   *
   * @deprecated Use {@link com.google.common.collect.Sets#intersection(Set, Set)} instead.
   */
  @Deprecated
  public static <T> Set<T> intersection(Set<? extends T> set1, Set<? extends T> set2) {
    Set<T> result = copyToSet(set1);
    result.retainAll(set2);
    return result;
  }

  private FeatureUtil() {}

        .testForwarding(
            Set.class,
            new Function<Set, Set>() {
              @Override
              public Set apply(Set delegate) {
                return wrap(delegate);
              }
            });
  }

  public void testEquals() {
    Set<String> set1 = ImmutableSet.of("one");
    Set<String> set2 = ImmutableSet.of("two");
    new EqualsTester()

  }

  /**
   * Construct a new {@link java.util.Set} that is the intersection of the given sets.
   *
   * @deprecated Use {@link com.google.common.collect.Sets#intersection(Set, Set)} instead.
   */
  @Deprecated
  public static <T> Set<T> intersection(Set<? extends T> set1, Set<? extends T> set2) {
    Set<T> result = copyToSet(set1);
    result.retainAll(set2);
    return result;
  }

  private FeatureUtil() {}

              }
            });
  }

  public void testEquals() {
    SortedMultiset<String> set1 = ImmutableSortedMultiset.of("one");
    SortedMultiset<String> set2 = ImmutableSortedMultiset.of("two");
    new EqualsTester()
        .addEqualityGroup(set1, wrap(set1), wrap(set1))
        .addEqualityGroup(set2, wrap(set2))
        .testEquals();
  }

  private static <T> SortedMultiset<T> wrap(SortedMultiset<T> delegate) {

        .testForwarding(
            Set.class,
            new Function<Set, Set>() {
              @Override
              public Set apply(Set delegate) {
                return wrap(delegate);
              }
            });
  }

  public void testEquals() {
    Set<String> set1 = ImmutableSet.of("one");
    Set<String> set2 = ImmutableSet.of("two");
    new EqualsTester()