}

    @Override
    public String toString() {
      return "BY_TO_STRING";
    }

    private Object readResolve() {
      return INSTANCE;
    }
  }

  // Always equal is a valid total ordering. And it works for any Object.
  private static final class AlwaysEqual extends Ordering<@Nullable Object>
      implements Serializable {
    private static final AlwaysEqual INSTANCE = new AlwaysEqual();

    }
  }

  // TODO(lukes): investigate using the @Contended annotation on these fields when jdk8 is
  // available.
  /**
   * This field encodes the current state of the future.
   *
   * <p>The valid values are:
   *
   * <ul>
   *   <li>{@code null} initial state, nothing has happened.
   *   <li>{@link Cancellation} terminal state, {@code cancel} was called.

  }

  public void test_contains_null_no() {
    Iterator<String> set = asList("a", "b").iterator();
    assertFalse(Iterators.contains(set, null));
  }

  public void testGetOnlyElement_noDefault_valid() {
    Iterator<String> iterator = Collections.singletonList("foo").iterator();
    assertEquals("foo", Iterators.getOnlyElement(iterator));
  }

  public void testGetOnlyElement_noDefault_empty() {

  private static <T extends @Nullable Object> void slowRemoveIfForRemainingElements(
      List<T> list, Predicate<? super T> predicate, int to, int from) {
    // Here we know that:
    // * (to < from) and that both are valid indices.
    // * Everything with (index < to) should be kept.
    // * Everything with (to <= index < from) should be removed.
    // * The element with (index == from) should be kept.

        int numHashFunctions,
        LockFreeBitArray bits);

    /**
     * Identifier used to encode this strategy, when marshalled as part of a BloomFilter. Only
     * values in the [-128, 127] range are valid for the compact serial form. Non-negative values
     * are reserved for enums defined in BloomFilterStrategies; negative values are reserved for any

      assertTrue(
          LongMath.biggestBinomials[k] == Integer.MAX_VALUE
              || !fitsInLong(BigIntegerMath.binomial(LongMath.biggestBinomials[k] + 1, k)));
      // In the first case, any long is valid; in the second, we want to test that the next-bigger
      // long overflows.
    }
    int k = LongMath.biggestBinomials.length;
    assertFalse(fitsInLong(BigIntegerMath.binomial(2 * k, k)));

    return asList(elements).iterator();
  }

  // In GWT, java.util.TreeSet throws ClassCastException when the comparator
  // throws it, unlike JDK6.  Therefore, we accept ClassCastException as a
  // valid result thrown by java.util.TreeSet#equals.
  private static void assertNotEqualLenient(TreeSet<?> unexpected, SortedSet<?> actual) {
    try {
      assertThat(actual).isNotEqualTo(unexpected);

      assertTrue(
          LongMath.biggestBinomials[k] == Integer.MAX_VALUE
              || !fitsInLong(BigIntegerMath.binomial(LongMath.biggestBinomials[k] + 1, k)));
      // In the first case, any long is valid; in the second, we want to test that the next-bigger
      // long overflows.
    }
    int k = LongMath.biggestBinomials.length;
    assertFalse(fitsInLong(BigIntegerMath.binomial(2 * k, k)));

  }

  public void test_contains_nonnull_iterable_no() {
    Iterable<String> set = iterable("a", "b");
    assertFalse(Iterables.contains(set, "c"));
  }

  public void testGetOnlyElement_noDefault_valid() {
    Iterable<String> iterable = Collections.singletonList("foo");
    assertEquals("foo", Iterables.getOnlyElement(iterable));
  }

  public void testGetOnlyElement_noDefault_empty() {

    return asList(elements).iterator();
  }

  // In GWT, java.util.TreeSet throws ClassCastException when the comparator
  // throws it, unlike JDK6.  Therefore, we accept ClassCastException as a
  // valid result thrown by java.util.TreeSet#equals.
  private static void assertNotEqualLenient(TreeSet<?> unexpected, SortedSet<?> actual) {
    try {
      assertThat(actual).isNotEqualTo(unexpected);