*/
  @get:Synchronized
  @set:Synchronized
  var idleCallback: Runnable? = null

  private var executorServiceOrNull: ExecutorService? = null

  @get:JvmName("executorService")
  @get:Synchronized
  val executorService: ExecutorService
    get() {
      if (executorServiceOrNull == null) {
        executorServiceOrNull =
          ThreadPoolExecutor(
            0,
            Int.MAX_VALUE,

    Collection<E> elements = getSampleElements(getNumElements() - 1);
    elements.add(null);

    collection = getSubjectGenerator().create(elements.toArray());
    assertTrue(
        "A Set should equal any other Set containing the same elements,"
            + " even if some elements are null.",
        getSet().equals(MinimalSet.from(elements)));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)

    SpliteratorTester.of(
            () ->
                CollectSpliterators.flatMap(
                    Arrays.spliterator(new String[] {"abc", "", "de", "f", "g", ""}),
                    (String str) -> str.isEmpty() ? null : charactersOf(str).spliterator(),
                    Spliterator.SIZED | Spliterator.DISTINCT | Spliterator.NONNULL,
                    7))
        .expect('a', 'b', 'c', 'd', 'e', 'f', 'g');
  }

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless

    Collection<E> elements = getSampleElements(getNumElements() - 1);
    elements.add(null);

    collection = getSubjectGenerator().create(elements.toArray());
    assertTrue(
        "A Set should equal any other Set containing the same elements,"
            + " even if some elements are null.",
        getSet().equals(MinimalSet.from(elements)));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)

  public void testEquals_otherListContainingNull() {
    List<E> other = new ArrayList<>(getSampleElements());
    other.set(other.size() / 2, null);
    assertFalse(
        "Two Lists should not be equal if exactly one of them has null at a given index.",
        getList().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  @CollectionFeature.Require(ALLOWS_NULL_VALUES)

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless

        encPart.add(new DERTaggedObject(true, 2, new DEROctetString(encryptedData)));
        v.add(new DERTaggedObject(true, 3, new DERSequence(encPart)));

        if (unknownTag != null) {
            v.add(new DERTaggedObject(true, unknownTag, new DERGeneralString("unknown")));
        }

        return new DERSequence(v).getEncoded();
    }

    /**

     * @return the stored or updated FailureUrl entity, or null if the exception should be ignored
     */
    public FailureUrl store(final CrawlingConfig crawlingConfig, final String errorName, final String url, final Throwable e) {
        if (e instanceof ContainerNotAvailableException) {
            return null;
        }

        final FailureUrlBhv bhv = ComponentUtil.getComponent(FailureUrlBhv.class);

          return null;
        }
      };

  // Escapes everything except [a-zA-Z0-9]
  private static final UnicodeEscaper SIMPLE_ESCAPER =
      new UnicodeEscaper() {
        @Override
        protected char @Nullable [] escape(int cp) {
          return ('a' <= cp && cp <= 'z') || ('A' <= cp && cp <= 'Z') || ('0' <= cp && cp <= '9')
              ? null