* {@code lexicographical(Collections.reverseOrder(comparator))} (consider how each would order
   * {@code [1]} and {@code [1, 1]}).
   */
  // Note: 90% of the time we don't add type parameters or wildcards that serve only to "tweak" the
  // desired return type. However, *nested* generics introduce a special class of problems that we
  // think tip it over into being worthwhile.

   * 9.0], [9.0, 10.0] (and so on), no matter what the function is. This guarantees that we handle
   * correctly requests of varying weight (permits), /no matter/ what the actual function is - so we
   * can tweak the latter freely. (The only requirement, obviously, is that we can compute its
   * integrals).
   *
   * Note well that if, for this function, we chose a horizontal line, at height of exactly (1/QPS),

            //
            // If we were to cancel taskFuture, that would let the next task start while the old
            // one is still running.
            //
            // Now, maybe we could tweak our implementation to not start the next task until the
            // callable actually completes. (We could detect completion in our wrapper
            // `AsyncCallable task`.) However, our contract also promises:

            //
            // If we were to cancel taskFuture, that would let the next task start while the old
            // one is still running.
            //
            // Now, maybe we could tweak our implementation to not start the next task until the
            // callable actually completes. (We could detect completion in our wrapper
            // `AsyncCallable task`.) However, our contract also promises:

   *   <li>clearing weak references to unreachable referents
   *   <li>enqueuing weak references to unreachable referents in their reference queue
   * </ul>
   */
  @DoNotMock("Implement with a lambda")
  public interface FinalizationPredicate {
    boolean isDone();
  }

  /**
   * Waits until the given weak reference is cleared, invoking the garbage collector as necessary to

   *   <li>clearing weak references to unreachable referents
   *   <li>enqueuing weak references to unreachable referents in their reference queue
   * </ul>
   */
  @DoNotMock("Implement with a lambda")
  public interface FinalizationPredicate {
    boolean isDone();
  }

  /**
   * Waits until the given weak reference is cleared, invoking the garbage collector as necessary to

 * #lock(int) strong} and {@linkplain #lazyWeakLock(int) weak} {@code Striped<Lock>}, {@linkplain
 * #semaphore(int, int) strong} and {@linkplain #lazyWeakSemaphore(int, int) weak} {@code
 * Striped<Semaphore>}, and {@linkplain #readWriteLock(int) strong} and {@linkplain
 * #lazyWeakReadWriteLock(int) weak} {@code Striped<ReadWriteLock>}. <i>Strong</i> means that all

    assertThat(spec.maximumSize).isEqualTo(20);
    assertThat(spec.maximumWeight).isNull();
    assertThat(spec.concurrencyLevel).isEqualTo(30);
    assertThat(spec.keyStrength).isEqualTo(Strength.WEAK);
    assertThat(spec.valueStrength).isEqualTo(Strength.WEAK);
    assertThat(spec.writeExpirationTimeUnit).isEqualTo(HOURS);
    assertThat(spec.accessExpirationTimeUnit).isEqualTo(MINUTES);
    assertThat(spec.writeExpirationDuration).isEqualTo(1L);

    checkStrength(map, Strength.WEAK, Strength.STRONG);
    assertThat(map.entryHelper)
        .isInstanceOf(MapMakerInternalMap.WeakKeyStrongValueEntry.Helper.class);
  }

  public void testSetWeakValues() {
    MapMakerInternalMap<Object, Object, ?, ?> map = makeMap(createMapMaker().weakValues());
    checkStrength(map, Strength.STRONG, Strength.WEAK);
    assertThat(map.entryHelper)

    checkStrength(map, Strength.WEAK, Strength.STRONG);
    assertThat(map.entryHelper)
        .isInstanceOf(MapMakerInternalMap.WeakKeyStrongValueEntry.Helper.class);
  }

  public void testSetWeakValues() {
    MapMakerInternalMap<Object, Object, ?, ?> map = makeMap(createMapMaker().weakValues());
    checkStrength(map, Strength.STRONG, Strength.WEAK);
    assertThat(map.entryHelper)