@Deprecated
  public static <T extends @Nullable Object> Ordering<T> from(Ordering<T> ordering) {
    return checkNotNull(ordering);
  }

  /**
   * Returns an ordering that compares objects according to the order in which they appear in the
   * given list. Only objects present in the list (according to {@link Object#equals}) may be
   * compared. This comparator imposes a "partial ordering" over the type {@code T}. Subsequent

  @Deprecated
  public static <T extends @Nullable Object> Ordering<T> from(Ordering<T> ordering) {
    return checkNotNull(ordering);
  }

  /**
   * Returns an ordering that compares objects according to the order in which they appear in the
   * given list. Only objects present in the list (according to {@link Object#equals}) may be
   * compared. This comparator imposes a "partial ordering" over the type {@code T}. Subsequent

      }
    }
    return dummy;
  }

  @Benchmark
  int ordering(int reps) {
    int dummy = 0;
    if (mutable) {
      for (int i = 0; i < reps; i++) {
        dummy += ORDERING.sortedCopy(input).get(0);
      }
    } else {
      for (int i = 0; i < reps; i++) {
        dummy += ORDERING.immutableSortedCopy(input).get(0);
      }
    }
    return dummy;
  }

   */
  private static final Comparator<?> NATURAL_ORDER = Ordering.natural();

  private static final ImmutableSortedMap<Comparable<?>, Object> NATURAL_EMPTY_MAP =
      new ImmutableSortedMap<>(
          ImmutableSortedSet.emptySet(Ordering.natural()), ImmutableList.<Object>of());

  static <K, V> ImmutableSortedMap<K, V> emptyMap(Comparator<? super K> comparator) {
    if (Ordering.natural().equals(comparator)) {
      return of();

      implements TestSetGenerator<UnhashableObject> {}

  private static Ordering<String> createExplicitComparator(String[] elements) {
    // Collapse equal elements, which Ordering.explicit() doesn't support, while
    // maintaining the ordering by first occurrence.
    Set<String> elementsPlus = Sets.newLinkedHashSet();
    elementsPlus.add(BEFORE_FIRST);

        assertEquals("1.2.3-20090413X094722-2", ArtifactUtils.toSnapshotVersion("1.2.3-20090413X094722-2"));
    }

    /**
     * Tests that the ordering of the map resembles the ordering of the input collection of artifacts.
     */
    @Test
    void testArtifactMapByVersionlessIdOrdering() throws Exception {
        List<Artifact> list = new ArrayList<>();

      }
    }
    return dummy;
  }

  @Benchmark
  int ordering(int reps) {
    int dummy = 0;
    if (mutable) {
      for (int i = 0; i < reps; i++) {
        dummy += ORDERING.sortedCopy(input).get(0);
      }
    } else {
      for (int i = 0; i < reps; i++) {
        dummy += ORDERING.immutableSortedCopy(input).get(0);
      }
    }
    return dummy;
  }

 * @author Ben Yu
 * @since 12.0
 */
@GwtIncompatible
@J2ktIncompatible
@ElementTypesAreNonnullByDefault
public final class ArbitraryInstances {

  private static final Ordering<Field> BY_FIELD_NAME =
      new Ordering<Field>() {
        @Override
        public int compare(Field left, Field right) {
          return left.getName().compareTo(right.getName());
        }
      };

  /**

      GeneralRange<@Nullable Integer> range = GeneralRange.downTo(ORDERING, 3, lBoundType);
      for (Integer i : IN_ORDER_VALUES) {
        assertEquals(
            ORDERING.compare(i, 3) > 0 || (ORDERING.compare(i, 3) == 0 && lBoundType == CLOSED),
            range.contains(i));
        assertEquals(
            ORDERING.compare(i, 3) < 0 || (ORDERING.compare(i, 3) == 0 && lBoundType == OPEN),
            range.tooLow(i));

   */
  @WeakOuter
  class Heap {
    final Ordering<E> ordering;

    @SuppressWarnings("nullness:initialization.field.uninitialized")
    @Weak
    Heap otherHeap; // always initialized immediately after construction

    Heap(Ordering<E> ordering) {
      this.ordering = ordering;
    }

    int compareElements(int a, int b) {
      return ordering.compare(elementData(a), elementData(b));
    }