*/
final class SingletonImmutableSet<E> extends ImmutableSet<E> {
  private final E element;

  SingletonImmutableSet(E element) {
    this.element = checkNotNull(element);
  }

  @Override
  public int size() {
    return 1;
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.singletonIterator(element);
  }

  @Override
  public boolean contains(@Nullable Object object) {

  fun enableHttp2() = enable(Http2::class)

  fun enableTaskRunner() = enable(TaskRunner::class)

  fun logHandler() =
    ConsoleHandler().apply {
      level = Level.FINE
      formatter =
        object : SimpleFormatter() {
          override fun format(record: LogRecord) = String.format("[%1\$tF %1\$tT] %2\$s %n", record.millis, record.message)
        }
    }

  fun enable(

      @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 1L;

      @Override
      public boolean contains(@Nullable Object element) {
        Preconditions.checkNotNull(element);
        return super.contains(element);
      }
    }
    Collection<Integer> nums = new CollectionThatThrowsNullPointerException<>();
    Predicate<@Nullable Integer> isFalse = Predicates.in(nums);

      for (Object o : extras) {
        sb.append(", ").append(o);
      }
      if (overflow) {
        sb.append(", ...");
      }
      sb.append('>');
      throw new IllegalArgumentException(sb.toString());
    }

    void add(Object o) {
      checkNotNull(o);
      if (element == null) {
        this.element = o;

    IllegalArgumentException expected =
        assertThrows(IllegalArgumentException.class, () -> getOnlyElement(iterator));
    assertThat(expected).hasMessageThat().isEqualTo("expected one element but was: <one, two>");
  }

  public void testGetOnlyElement_noDefault_fiveElements() {
    Iterator<String> iterator = asList("one", "two", "three", "four", "five").iterator();
    IllegalArgumentException expected =

      char tmp = array[i];
      array[i] = array[j];
      array[j] = tmp;
    }
  }

  /**
   * Performs a right rotation of {@code array} of "distance" places, so that the first element is
   * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance
   * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Chars.asList(array),

  @Override
  void setCountCheckReturnValue(E element, int count) {
    assertTrue(
        "setCount() with the correct expected present count should return true",
        setCount(element, count));
  }

  @Override
  void setCountNoCheckReturnValue(E element, int count) {
    setCount(element, count);
  }

  @CanIgnoreReturnValue
  private boolean setCount(E element, int count) {

    int expectedHashCode = 0;
    for (E element : elements) {
      expectedHashCode += (element == null) ? 0 : element.hashCode();
    }

    elements.add(null);
    collection = getSubjectGenerator().create(elements.toArray());
    assertEquals(
        "A Set's hashCode() should be the sum of those of its elements (with "
            + "a null element counting as having a hash of zero).",
        expectedHashCode,

        logs += "${logRecord.level}: ${logRecord.message}"
      }

      override fun flush() {
      }

      override fun close() {
      }
    }

  private var previousLevel: Level? = null

  override fun beforeEach(context: ExtensionContext?) {
    previousLevel = logger.level
    logger.addHandler(handler)
    logger.setLevel(Level.FINEST)
  }

   * though we also allow it to "succeed" if neither is permitted.
   */

  private void assertSetCount(E element, int count) {
    setCountCheckReturnValue(element, count);

    assertEquals(
        "multiset.count() should return the value passed to setCount()",
        count,
        getMultiset().count(element));

    int size = 0;
    for (Multiset.Entry<E> entry : getMultiset().entrySet()) {