}

    /**
     * @throws Exception
     */
    @Test
    public void testRemoveLast() throws Exception {
        list.addLast("1");
        list.addLast("2");
        list.removeLast();
        assertThat(list.getLast(), is("1"));
    }

    /**
     * @throws Exception
     */
    @Test
    public void testAddFirst() throws Exception {
        list.addFirst("1");

 * defined as the <i>least</i> element in the queue according to the queue's comparator. But unlike
 * a regular priority queue, the methods {@link #peekLast}, {@link #pollLast} and {@link
 * #removeLast} are also provided, to act on the <i>greatest</i> element in the queue instead.
 *
 * <p>A min-max priority queue can be configured with a maximum size. If so, each time the size of

        final E first = header.next.element;
        header.next.remove();
        return first;
    }

    /**
     * 最後の要素を削除します。
     *
     * @return 最後の要素
     */
    public E removeLast() {
        if (isEmpty()) {
            throw new NoSuchElementException();
        }
        final E last = header.previous.element;
        header.previous.remove();
        return last;
    }

 * defined as the <i>least</i> element in the queue according to the queue's comparator. But unlike
 * a regular priority queue, the methods {@link #peekLast}, {@link #pollLast} and {@link
 * #removeLast} are also provided, to act on the <i>greatest</i> element in the queue instead.
 *
 * <p>A min-max priority queue can be configured with a maximum size. If so, each time the size of

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

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

    @Override
    @CheckForNull
    public E pollFirst() {
      synchronized (mutex) {
        return delegate().pollFirst();

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

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

    @Override
    @CheckForNull
    public E pollFirst() {
      synchronized (mutex) {
        return delegate().pollFirst();

    Deque<Spliterator<T>> splits = new ArrayDeque<>();
    splits.addLast(stream.spliterator());

    while (!splits.isEmpty()) {
      Spliterator<T> spliterator = splits.removeLast();

      if (spliterator.getExactSizeIfKnown() == 0) {
        continue; // drop this split
      }

      // Many spliterators will have trySplits that are SUBSIZED even if they are not themselves

    Deque<Spliterator<T>> splits = new ArrayDeque<>();
    splits.addLast(stream.spliterator());

    while (!splits.isEmpty()) {
      Spliterator<T> spliterator = splits.removeLast();

      if (spliterator.getExactSizeIfKnown() == 0) {
        continue; // drop this split
      }

      // Many spliterators will have trySplits that are SUBSIZED even if they are not themselves

          if (topConcat.metaIterators != null) {
            while (!topConcat.metaIterators.isEmpty()) {
              this.metaIterators.addFirst(topConcat.metaIterators.removeLast());
            }
          }
          this.topMetaIterator = topConcat.topMetaIterator;
        }
      }
      return true;
    }

    @Override
    @ParametricNullness