finalizeReferentCalled = true;
    }
  }

  /**
   * Keeps a weak reference to the underlying reference queue. When this reference is cleared, we
   * know that the background thread has stopped and released its strong reference.
   */
  private WeakReference<ReferenceQueue<Object>> queueReference;

  @Test
  public void testThatFinalizerStops() {
    weaklyReferenceQueue();

 *       identically to {@code Nullable}</a> as of version 0.9.9.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>, maybe: It might no longer be
 *       necessary there, since we have stopped using the {@code @ParametersAreNonnullByDefault}
 *       annotations that {@code ParametricNullness} was counteracting.
 * </ul>
 *
 * <p>This annotation is a temporary hack. We will remove it after <a

 *       identically to {@code Nullable}</a> as of version 0.9.9.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>, maybe: It might no longer be
 *       necessary there, since we have stopped using the {@code @ParametersAreNonnullByDefault}
 *       annotations that {@code ParametricNullness} was counteracting.
 * </ul>
 *
 * <p>This annotation is a temporary hack. We will remove it after <a

 *       identically to {@code Nullable}</a> as of version 0.9.9.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>, maybe: It might no longer be
 *       necessary there, since we have stopped using the {@code @ParametersAreNonnullByDefault}
 *       annotations that {@code ParametricNullness} was counteracting.
 * </ul>
 *
 * <p>This annotation is a temporary hack. We will remove it after <a

 *       identically to {@code Nullable}</a> as of version 0.9.9.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>, maybe: It might no longer be
 *       necessary there, since we have stopped using the {@code @ParametersAreNonnullByDefault}
 *       annotations that {@code ParametricNullness} was counteracting.
 * </ul>
 *
 * <p>This annotation is a temporary hack. We will remove it after <a

 *       identically to {@code Nullable}</a> as of version 0.9.9.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>, maybe: It might no longer be
 *       necessary there, since we have stopped using the {@code @ParametersAreNonnullByDefault}
 *       annotations that {@code ParametricNullness} was counteracting.
 * </ul>
 *
 * <p>This annotation is a temporary hack. We will remove it after <a

        } catch (final ContainerNotAvailableException e) {
            if (logger.isDebugEnabled()) {
                logger.debug("Crawler is stopped.", e);
            } else if (logger.isInfoEnabled()) {
                logger.info("Crawler is stopped.");
            }
            exitCode = Constants.EXIT_FAIL;
        } catch (final Throwable t) {
            logger.error("Crawler does not work correctly.", t);

        }

        try {
            dataIndexHelper.crawl("test-session-force-stop");
            assertTrue("Should exit quickly when force stopped", true);
        } catch (Exception e) {
            assertTrue("Force stop should handle exceptions quickly", true);
        }
    }

    public void test_crawl_with_short_intervals() {
        try {

                } finally {
                    if (systemHelper.isForceStop()) {
                        finishCrawling = true;
                        if (logger.isDebugEnabled()) {
                            logger.debug("Stopped indexUpdater.");
                        }
                    }
                }

                if (emptyListCount >= maxEmptyListCount) {
                    if (logger.isInfoEnabled()) {

        Executors.newSingleThreadScheduledExecutor(new ThreadFactoryImpl());
    // Add a listener to shut down the executor after the service is stopped. This ensures that the
    // JVM shutdown will not be prevented from exiting after this service has stopped or failed.
    // Technically this listener is added after start() was called so it is a little gross, but it