public <T> T[] toArray(T[] array) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.toArray(array);
    }

    @Override
    public void addFirst(E e) {
      assertTrue(Thread.holdsLock(mutex));
      delegate.addFirst(e);
    }

    @Override
    public void addLast(E e) {
      assertTrue(Thread.holdsLock(mutex));
      delegate.addLast(e);
    }

    @Override

  }

  public TearDownStack(boolean suppressThrows) {
    this.suppressThrows = suppressThrows;
  }

  @Override
  public final void addTearDown(TearDown tearDown) {
    synchronized (lock) {
      stack.addFirst(checkNotNull(tearDown));
    }
  }

  /** Causes teardown to execute. */
  public final void runTearDown() {
    List<Throwable> exceptions = new ArrayList<>();
    List<TearDown> stackCopy;

  }

  public TearDownStack(boolean suppressThrows) {
    this.suppressThrows = suppressThrows;
  }

  @Override
  public final void addTearDown(TearDown tearDown) {
    synchronized (lock) {
      stack.addFirst(checkNotNull(tearDown));
    }
  }

  /** Causes teardown to execute. */
  public final void runTearDown() {
    List<Throwable> exceptions = new ArrayList<>();
    List<TearDown> stackCopy;

    }

    @Override
    Deque<E> delegate() {
      return (Deque<E>) super.delegate();
    }

    @Override
    public void addFirst(E e) {
      synchronized (mutex) {
        delegate().addFirst(e);
      }
    }

    @Override
    public void addLast(E e) {
      synchronized (mutex) {
        delegate().addLast(e);
      }
    }

    }

    @Override
    Deque<E> delegate() {
      return (Deque<E>) super.delegate();
    }

    @Override
    public void addFirst(E e) {
      synchronized (mutex) {
        delegate().addFirst(e);
      }
    }

    @Override
    public void addLast(E e) {
      synchronized (mutex) {
        delegate().addLast(e);
      }
    }

            this.metaIterators = new ArrayDeque<>();
          }
          this.metaIterators.addFirst(this.topMetaIterator);
          if (topConcat.metaIterators != null) {
            while (!topConcat.metaIterators.isEmpty()) {
              this.metaIterators.addFirst(topConcat.metaIterators.removeLast());
            }
          }
          this.topMetaIterator = topConcat.topMetaIterator;