// null versus non-null.
    a = Arrays.<@Nullable Integer>asList(4, 8, 15, null, 23, 42);
    b = asList(4, 8, 15, 16, 23, 42);
    assertFalse(elementsEqual(a.iterator(), b.iterator()));
    assertFalse(elementsEqual(b.iterator(), a.iterator()));

    // Different lengths.
    a = asList(4, 8, 15, 16, 23);
    b = asList(4, 8, 15, 16, 23, 42);

        ImmutableSortedSet.copyOf(LegacyComparable.VALUES_BACKWARD);
    assertTrue(elementsEqual(LegacyComparable.VALUES_FORWARD, set));
  }

  public void testLegacyComparable_copyOf_iterator() {
    ImmutableSortedSet<LegacyComparable> set =
        ImmutableSortedSet.copyOf(LegacyComparable.VALUES_BACKWARD.iterator());
    assertTrue(elementsEqual(LegacyComparable.VALUES_FORWARD, set));
  }

        ImmutableSortedSet.copyOf(LegacyComparable.VALUES_BACKWARD);
    assertTrue(elementsEqual(LegacyComparable.VALUES_FORWARD, set));
  }

  public void testLegacyComparable_copyOf_iterator() {
    ImmutableSortedSet<LegacyComparable> set =
        ImmutableSortedSet.copyOf(LegacyComparable.VALUES_BACKWARD.iterator());
    assertTrue(elementsEqual(LegacyComparable.VALUES_FORWARD, set));
  }

    // null versus non-null.
    a = Arrays.<@Nullable Integer>asList(4, 8, 15, null, 23, 42);
    b = asList(4, 8, 15, 16, 23, 42);
    assertFalse(elementsEqual(a.iterator(), b.iterator()));
    assertFalse(elementsEqual(b.iterator(), a.iterator()));

    // Different lengths.
    a = asList(4, 8, 15, 16, 23);
    b = asList(4, 8, 15, 16, 23, 42);

    b = asList(4, 8, 15, 16, 23, 42);
    assertTrue(elementsEqual(a, b));

    // An element differs.
    a = asList(4, 8, 15, 12, 23, 42);
    b = asList(4, 8, 15, 16, 23, 42);
    assertFalse(elementsEqual(a, b));

    // null versus non-null.
    a = Arrays.<@Nullable Integer>asList(4, 8, 15, null, 23, 42);
    b = asList(4, 8, 15, 16, 23, 42);
    assertFalse(elementsEqual(a, b));
    assertFalse(elementsEqual(b, a));