* log n) on average.
     *
     * <p>The online hash flooding detecting in RegularSetBuilderImpl.add can detect e.g. many
     * exactly matching hash codes, which would cause construction to take O(n^2), but can't detect
     * e.g. hash codes adversarially designed to go into ascending table locations, which keeps
     * construction O(n) (as desired) but then can have O(n) queries later.

/**
 * The {@code CycleDetectingLockFactory} creates {@link ReentrantLock} instances and {@link
 * ReentrantReadWriteLock} instances that detect potential deadlock by checking for cycles in lock
 * acquisition order.
 *
 * <p>Potential deadlocks detected when calling the {@code lock()}, {@code lockInterruptibly()}, or
 * {@code tryLock()} methods will result in the execution of the {@link Policy} specified when

    assertEquals("2", iterator.next());
    assertEquals("3", iterator.next());
    assertEquals("4", iterator.next());
    assertEquals(4, iterator.nextIndex());
    try {
      iterator.next();
      fail("did not detect end of list");
    } catch (NoSuchElementException expected) {
    }
    assertEquals(3, iterator.previousIndex());
    assertEquals("4", iterator.previous());
    assertEquals("3", iterator.previous());

    try {
      new NullPointerTester().testInstanceMethods(instance, visibility);
    } catch (AssertionFailedError expected) {
      return;
    }
    fail("Should detect problem in " + instance.getClass().getSimpleName());
  }

  private static void shouldFail(Object instance) {
    shouldFail(instance, Visibility.PACKAGE);
    shouldFail(instance, Visibility.PROTECTED);

    assertEquals("2", iterator.next());
    assertEquals("3", iterator.next());
    assertEquals("4", iterator.next());
    assertEquals(4, iterator.nextIndex());
    try {
      iterator.next();
      fail("did not detect end of list");
    } catch (NoSuchElementException expected) {
    }
    assertEquals(3, iterator.previousIndex());
    assertEquals("4", iterator.previous());
    assertEquals("3", iterator.previous());

    // load timeout multiplier.  Or we could try to use a CPU time bound instead of wall clock time
    // bound.  But these ideas are harder to implement.  We do not try to detect or handle a
    // user-specified -XX:+DisableExplicitGC.
    //
    // TODO(user): Consider using
    // java/lang/management/OperatingSystemMXBean.html#getSystemLoadAverage()
    //

   * It is possible for a Cell to become unused when threads that
   * once hashed to it terminate, as well as in the case where
   * doubling the table causes no thread to hash to it under
   * expanded mask.  We do not try to detect or remove such cells,
   * under the assumption that for long-running instances, observed
   * contention levels will recur, so the cells will eventually be
   * needed again; and for short-lived ones, it does not matter.
   */

            // 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:
            //
            // 2. not to cancel any Future the user returned from an AsyncCallable
            //

   * It is possible for a Cell to become unused when threads that
   * once hashed to it terminate, as well as in the case where
   * doubling the table causes no thread to hash to it under
   * expanded mask.  We do not try to detect or remove such cells,
   * under the assumption that for long-running instances, observed
   * contention levels will recur, so the cells will eventually be
   * needed again; and for short-lived ones, it does not matter.
   */

    // load timeout multiplier.  Or we could try to use a CPU time bound instead of wall clock time
    // bound.  But these ideas are harder to implement.  We do not try to detect or handle a
    // user-specified -XX:+DisableExplicitGC.
    //
    // TODO(user): Consider using
    // java/lang/management/OperatingSystemMXBean.html#getSystemLoadAverage()
    //