* If we make some other optimizations, this one will no longer be necessary. The optimization
       * could actually hurt in some cases, as it forces us to keep all inputs in memory until the
       * final input completes.
       */
      @RetainedLocalRef
      ImmutableCollection<? extends ListenableFuture<? extends InputT>> localFutures = futures;

            return OptionalThing.empty();
        }
        return OptionalThing.of(pipeline);
    }

    /**
     * Refreshes the crawling configuration cache by invalidating all cached entries.
     * This forces the next access to reload configurations from the underlying services.
     */
    public void refresh() {
        crawlingConfigCache.invalidateAll();
    }

    /**

    // avoids this.
    checkState(aBoolean, "", aBoolean ? "" : anInt, (Object) anInt);

    // ambiguous without the .booleanValue() call since the boxing forces us into phase 2 resolution
    short s = 2;
    checkState(boxedBoolean.booleanValue(), "", s);
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointers() {
    /*

    // avoids this.
    checkState(aBoolean, "", aBoolean ? "" : anInt, (Object) anInt);

    // ambiguous without the .booleanValue() call since the boxing forces us into phase 2 resolution
    short s = 2;
    checkState(boxedBoolean.booleanValue(), "", s);
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointers() {
    /*

          <show>package</show>
        </configuration>
      </plugin>
      <!-- Disable "normal" testing, which doesn't work for GWT tests. -->
      <plugin>

 * </ul>
 *
 * <p>Disadvantages compared to {@code long[]}:
 *
 * <ul>
 *   <li>Memory footprint has a fixed overhead (about 24 bytes per instance).
 *   <li><i>Some</i> construction use cases force the data to be copied (though several construction
 *       APIs are offered that don't).
 *   <li>Can't be passed directly to methods that expect {@code long[]} (though the most common
 *       utilities do have replacements here).

 * </ul>
 *
 * <p>Disadvantages compared to {@code int[]}:
 *
 * <ul>
 *   <li>Memory footprint has a fixed overhead (about 24 bytes per instance).
 *   <li><i>Some</i> construction use cases force the data to be copied (though several construction
 *       APIs are offered that don't).
 *   <li>Can't be passed directly to methods that expect {@code int[]} (though the most common
 *       utilities do have replacements here).

        }

        int startedCrawlerNum = 0;
        int activeCrawlerNum = 0;
        while (startedCrawlerNum < dataCrawlingThreadList.size()) {
            // Force to stop crawl
            if (systemHelper.isForceStop()) {
                for (final DataCrawlingThread crawlerThread : dataCrawlingThreadList) {
                    crawlerThread.stopCrawling();
                }

 *
 * <p>Disadvantages of EventBus include:
 *
 * <ul>
 *   <li>It makes the cross-references between producer and subscriber harder to find. This can
 *       complicate debugging, lead to unintentional reentrant calls, and force apps to eagerly
 *       initialize all possible subscribers at startup time.
 *   <li>It uses reflection in ways that break when code is processed by optimizers/minimizers like

        });
        indexUpdater.start();

        int startedCrawlerNum = 0;
        int activeCrawlerNum = 0;
        try {
            while (startedCrawlerNum < crawlerList.size()) {
                // Force to stop crawl
                if (systemHelper.isForceStop()) {
                    for (final Crawler crawler : crawlerList) {
                        crawler.stop();
                    }
                    break;