.test();
  }

  public void testPairwiseEquivalent_equals() {
    new EqualsTester()
        .addEqualityGroup(Equivalence.equals().pairwise(), Equivalence.equals().pairwise())
        .addEqualityGroup(Equivalence.identity().pairwise())
        .testEquals();
  }

  private enum LengthFunction implements Function<String, Integer> {
    INSTANCE;

    @Override
    public Integer apply(String input) {

 * @author Louis Wasserman
 */
@GwtCompatible
public final class Comparators {
  private Comparators() {}

  /**
   * Returns a new comparator which sorts iterables by comparing corresponding elements pairwise
   * until a nonzero result is found; imposes "dictionary order." If the end of one iterable is
   * reached, but not the other, the shorter iterable is considered to be less than the longer one.

        toImmutableSortedMap(Entry::getKey, Entry::getValue, Integer::sum);
    Equivalence<ImmutableMap<String, Integer>> equivalence =
        Equivalence.equals().<Entry<String, Integer>>pairwise().onResultOf(ImmutableMap::entrySet);
    CollectorTester.of(collector, equivalence)
        .expectCollects(
            ImmutableSortedMap.of("one", 1, "three", 3, "two", 4),
            mapEntry("one", 1),

 * @author Louis Wasserman
 */
@GwtCompatible
public final class Comparators {
  private Comparators() {}

  /**
   * Returns a new comparator which sorts iterables by comparing corresponding elements pairwise
   * until a nonzero result is found; imposes "dictionary order." If the end of one iterable is
   * reached, but not the other, the shorter iterable is considered to be less than the longer one.

      Iterable<? extends Comparator<? super T>> comparators) {
    return new CompoundOrdering<>(comparators);
  }

  /**
   * Returns a new ordering which sorts iterables by comparing corresponding elements pairwise until
   * a nonzero result is found; imposes "dictionary order". If the end of one iterable is reached,
   * but not the other, the shorter iterable is considered to be less than the longer one. For

      Iterable<? extends Comparator<? super T>> comparators) {
    return new CompoundOrdering<>(comparators);
  }

  /**
   * Returns a new ordering which sorts iterables by comparing corresponding elements pairwise until
   * a nonzero result is found; imposes "dictionary order". If the end of one iterable is reached,
   * but not the other, the shorter iterable is considered to be less than the longer one. For

<p>
The type <code>T</code> in a term of the form <code>T</code> or <code>~T</code> cannot
be a <a href="#Type_parameter_declarations">type parameter</a>, and the type sets of all
non-interface terms must be pairwise disjoint (the pairwise intersection of the type sets must be empty).
Given a type parameter <code>P</code>:
</p>

<pre>
interface {
	P                // illegal: P is a type parameter