* value is undefined.
     *
     * @return The location of the problem, never {@code null}.
     */
    String getLocation();

    /**
     * Gets the exception that caused this problem (if any).
     *
     * @return The exception that caused this problem or {@code null} if not applicable.
     */
    Exception getException();

    /**
     * Gets the message that describes this problem.

        for (Vertex v : children) {
            DfsState state = stateMap.putIfAbsent(v, DfsState.VISITING);
            if (state == null) {
                cycle.addLast(v.label);
                List<String> ret = visitCycle(v.children, stateMap, cycle);
                if (ret != null) {
                    return ret;
                }
                cycle.removeLast();
                stateMap.put(v, DfsState.VISITED);

   */
  var idleCallback: Runnable? = null
    get() = this.withLock { field }
    set(value) {
      this.withLock { field = value }
    }

  private var executorServiceOrNull: ExecutorService? = null

  @get:JvmName("executorService")
  val executorService: ExecutorService
    get() =
      this.withLock {
        if (executorServiceOrNull == null) {
          executorServiceOrNull =

                .source(nonNull(source, "source cannot be null"))
                .build();
    }

    @Nonnull
    static ProjectBuilderRequest build(@Nonnull Session session, @Nonnull Path path) {
        return builder()
                .session(nonNull(session, "session cannot be null"))
                .path(nonNull(path, "path cannot be null"))
                .build();
    }

    @Execute
    public HtmlResponse index() {
        getSession().ifPresent(session -> session.removeAttribute(INVALID_OLD_PASSWORD));
        return asIndexPage(null).useForm(LoginForm.class);
    }

    private HtmlResponse asIndexPage(final LoginForm form) {
        if (form != null) {
            form.clearSecurityInfo();
        }
        return asHtml(virtualHost(path_Login_IndexJsp)).renderWith(data -> {

  private @interface GwtTransient {}

  /**
   * Compares strings in natural order except that null comes immediately before a given value. This
   * works better than Ordering.natural().nullsFirst() because, if null comes before all other
   * values, it lies outside the submap/submultiset ranges we test, and the variety of tests that
   * exercise null handling fail on those subcollections.
   */

    }

    public static UrlQueue<?> getUrlQueue() {
        return URL_QUEUE_THREAD_LOCAL.get();
    }

    public static void setUrlQueue(final UrlQueue<?> urlQueue) {
        if (urlQueue == null) {
            URL_QUEUE_THREAD_LOCAL.remove();
        } else {
            URL_QUEUE_THREAD_LOCAL.set(urlQueue);
        }
    }

    public static CrawlerContext getCrawlerContext() {

      return;
    }

    map.put(null, unmappedValue);
    assertEquals(unmappedValue, map.get(null));
    assertTrue(map.containsKey(null));
    Entry<@Nullable K, V> entry = mapEntry(null, unmappedValue);
    assertTrue(entrySet.remove(entry));
    assertNull(map.get(null));
    assertFalse(map.containsKey(null));
  }

  public void testEntrySetRemoveNullKeyMissing() {

        existPrePage = false;
        existNextPage = false;
        pageSize = getDefaultPageSize();
        currentPageNumber = getDefaultCurrentPageNumber();

        id = null;
        name = null;
        versionNo = null;

    }

    protected int getDefaultCurrentPageNumber() {
        return DEFAULT_CURRENT_PAGE_NUMBER;
    }

    public int getAllRecordCount() {
        return allRecordCount;

        newInterfaces.keySet().removeAll(oldInterfaces.keySet())

        if (newInterfaces.isEmpty()) {
            return null
        }

        List<String> changes = filterChangesToReport(newClass, newInterfaces)
        if (changes.isEmpty()) {
            return null
        }
        return acceptOrReject(c, changes, Violation.error(c, " introduces internal or incubating interfaces"))
    }