* Returns an {@link Optional} containing the first element in this fluent iterable. If the
   * iterable is empty, {@code Optional.absent()} is returned.
   *
   * <p><b>{@code Stream} equivalent:</b> if the goal is to obtain any element, {@link
   * Stream#findAny}; if it must specifically be the <i>first</i> element, {@code Stream#findFirst}.
   *
   * @throws NullPointerException if the first element is null; if this is a possibility, use {@code

    assertEquals("Should be able to peek() at first element", "A", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() first element multiple times", "A", peekingIterator.peek());
    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());
    assertEquals(

    }

    /**
     * Adds {@code element} to the {@code ImmutableSortedMultiset}.
     *
     * @param element the element to add
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code element} is null
     */
    @CanIgnoreReturnValue
    @Override
    public Builder<E> add(E element) {
      super.add(element);
      return this;
    }

    /**

            Element root = document.root();
            Element profiles = root.child("profiles").orElse(null);
            Element profile = profiles.child("profile").orElse(null);
            Element profileBuild = profile.child("build").orElse(null);
            Element profilePlugins = profileBuild.child("plugins").orElse(null);
            Element antrunPlugin = profilePlugins

  final transient E element;

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

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

  @Override
  public boolean contains(@Nullable Object target) {
    return element.equals(target);
  }

  @Override
  public UnmodifiableIterator<E> iterator() {

    /**
     * Return the index of the next lower element in the list, or {@code -1} if there is no such
     * element.
     */
    NEXT_LOWER {
      @Override
      int resultIndex(int higherIndex) {
        return higherIndex - 1;
      }
    },
    /**
     * Return the index of the next higher element in the list, or {@code list.size()} if there is
     * no such element.
     */
    NEXT_HIGHER {

                Map<Object, Object> context = Collections.emptyMap();

                for (Plugin element : src) {
                    Object key = getPluginKey(element);
                    managedPlugins.put(key, element);
                }

                for (Plugin element : tgt) {
                    Object key = getPluginKey(element);
                    Plugin managedPlugin = managedPlugins.get(key);

   * stream.filter(element::equals).count()}. If {@code element} might be null, use {@code
   * stream.filter(Predicate.isEqual(element)).count()} instead.
   *
   * @see java.util.Collections#frequency(Collection, Object) Collections.frequency(Collection,
   *     Object)
   */
  public static int frequency(Iterable<?> iterable, @Nullable Object element) {
    if ((iterable instanceof Multiset)) {

   * 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()) {

    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,