*
   * <p><b>Java 21+ users:</b> if {code iterable} is a {@code SequencedCollection} (e.g., any list),
   * consider using {@code collection.getFirst()} instead. Note that if the collection is empty,
   * {@code getFirst()} throws a {@code NoSuchElementException}, while this method returns the
   * default value.
   *
   * @param defaultValue the default value to return if the iterable is empty

  public void testGetFirst_withDefault_singleton() {
    Iterable<String> iterable = singletonList("foo");
    assertThat(Iterables.getFirst(iterable, "bar")).isEqualTo("foo");
  }

  public void testGetFirst_withDefault_empty() {
    Iterable<String> iterable = emptyList();
    assertThat(Iterables.getFirst(iterable, "bar")).isEqualTo("bar");
  }

  public void testGetFirst_withDefault_empty_null() {

   * @since 12.0
   */
  @Override
  public @Nullable E ceiling(E e) {
    return Iterables.<@Nullable E>getFirst(tailSet(e, true), null);
  }

  /**
   * @since 12.0
   */
  @GwtIncompatible // NavigableSet
  @Override
  public @Nullable E higher(E e) {
    return Iterables.<@Nullable E>getFirst(tailSet(e, false), null);
  }

  @Override
  public E first() {
    return iterator().next();
  }

                pop();
                inPara = true;
            }
        }
        stack.getFirst().appendChild(node);
        if (inPara) {
            Element para = document.createElement("para");
            push(para);
        }
    }

    public void push(Element element) {
        stack.getFirst().appendChild(element);

            this.visitor = visitor;
        }

        private void unwindTo(String element, TokenVisitor visitor) {
            if (elementStack.contains(element)) {
                while (!elementStack.getFirst().equals(element)) {
                    visitor.onEndHtmlElement(elementStack.removeFirst());
                }
                elementStack.removeFirst();
                visitor.onEndHtmlElement(element);
            }

     */
    @Test
    public void testGetFirst() throws Exception {
        try {
            list.getFirst();
            fail();
        } catch (final NoSuchElementException ex) {
            System.out.println(ex);
        }
        list.addFirst("1");
        assertThat(list.getFirst(), is("1"));
    }

    /**
     * @throws Exception
     */
    @Test

    public @Nullable E pollLast() {
      synchronized (mutex) {
        return delegate().pollLast();
      }
    }

    @Override
    public E getFirst() {
      synchronized (mutex) {
        return delegate().getFirst();
      }
    }

    @Override
    public E getLast() {
      synchronized (mutex) {
        return delegate().getLast();
      }
    }

   *
   * @throws NullPointerException if the first element is null; if this is a possibility, use {@code
   *     iterator().next()} or {@link Iterables#getFirst} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();

   *
   * @throws NullPointerException if the first element is null; if this is a possibility, use {@code
   *     iterator().next()} or {@link Iterables#getFirst} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();

    public @Nullable E pollLast() {
      synchronized (mutex) {
        return delegate().pollLast();
      }
    }

    @Override
    public E getFirst() {
      synchronized (mutex) {
        return delegate().getFirst();
      }
    }

    @Override
    public E getLast() {
      synchronized (mutex) {
        return delegate().getLast();
      }
    }