- [ ] Your pull request should address just one issue, without pulling in other changes.
- [ ] Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
- [ ] Each commit in the pull request should have a meaningful subject line and body.
  Note that commits might be squashed by a maintainer on merge.

  static final AllEqualOrdering INSTANCE = new AllEqualOrdering();

  @Override
  @SuppressWarnings("UnusedVariable") // intentionally weird Comparator
  public int compare(@Nullable Object left, @Nullable Object right) {
    return 0;
  }

  @Override
  public <E extends @Nullable Object> List<E> sortedCopy(Iterable<E> iterable) {
    return Lists.newArrayList(iterable);
  }

  @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 NavigableMap<K, V> delegate;

  public SafeTreeMap() {
    this(new TreeMap<K, V>());
  }

    // Pretend the comparator can compare anything. If it turns out it can't
    // compare a and b, we should get a CCE or NPE on the subsequent line. Only methods
    // that are spec'd to throw CCE and NPE should call this.
    @SuppressWarnings({"unchecked", "nullness"})
    Comparator<@Nullable Object> unsafeComparator = (Comparator<@Nullable Object>) comparator;
    return unsafeComparator.compare(a, b);
  }

    this.nextOrNull = firstOrNull;
  }

  /**
   * Returns the element that follows {@code previous}, or returns {@code null} if no elements
   * remain. This method is invoked during each call to {@link #next()} in order to compute the
   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {
    return nextOrNull != null;
  }

  ExplicitOrdering(List<T> valuesInOrder) {
    this(Maps.indexMap(valuesInOrder));
  }

  ExplicitOrdering(ImmutableMap<T, Integer> rankMap) {
    this.rankMap = rankMap;
  }

  @Override
  public int compare(T left, T right) {
    return rank(left) - rank(right); // safe because both are nonnegative
  }

  private int rank(T value) {
    Integer rank = rankMap.get(value);
    if (rank == null) {

  @Override
  public String toString() {
    return "DontHashMe" + value;
  }

  @Override
  public int compareTo(UnhashableObject o) {
    return Integer.compare(this.value, o.value);
  }

@GwtCompatible
final class UsingToStringOrdering extends Ordering<Object> implements Serializable {
  static final UsingToStringOrdering INSTANCE = new UsingToStringOrdering();

  @Override
  public int compare(Object left, Object right) {
    return left.toString().compareTo(right.toString());
  }

  // preserve singleton-ness, so equals() and hashCode() work correctly
  private Object readResolve() {
    return INSTANCE;

    (For example, a function in a library to compute square roots has
    a purpose that is entirely well-defined independent of the
    application.  Therefore, Subsection 2d requires that any
    application-supplied function or table used by this function must
    be optional: if the application does not supply it, the square
    root function must still compute square roots.)

 * </ul>
 * <p>
 * Example usage:
 * <pre>
 * RequestCache cache = cacheFactory.createCache();
 * Result result = cache.request(myRequest, req -> {
 *     // Expensive operation to compute result
 *     return computedResult;
 * });
 * </pre>
 * <p>
 * The package also provides support for batch operations through {@link org.apache.maven.api.cache.BatchRequestException}