public Entry<E> firstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  @CheckForNull
  public Entry<E> lastEntry() {
    Iterator<Entry<E>> entryIterator = descendingEntryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  @CheckForNull
  public Entry<E> pollFirstEntry() {

  public Entry<E> firstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  @CheckForNull
  public Entry<E> lastEntry() {
    Iterator<Entry<E>> entryIterator = descendingEntryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  @CheckForNull
  public Entry<E> pollFirstEntry() {

     */
    @Test
    public void testHasNext() {
        final ArrayIterator<String> itr = new ArrayIterator<String>("A", "B");
        assertThat(itr.hasNext(), is(true));
        itr.next();
        assertThat(itr.hasNext(), is(true));
        itr.next();
        assertThat(itr.hasNext(), is(not(true)));
    }

    /**
     * @throws Exception
     */
    @Test
    public void testRemove() throws Exception {

    assertTrue(iterator.hasNext());
    assertEquals("a", iterator.next());
    try {
      iterator.remove();
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  @SuppressWarnings("DoNotCall")
  public void testAdd() {
    ListIterator<String> iterator = create();

    assertTrue(iterator.hasNext());
    assertEquals("a", iterator.next());

    assertEquals(rangeSet.asDescendingSetOfRanges().isEmpty(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asRanges().iterator().hasNext(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asDescendingSetOfRanges().iterator().hasNext(), rangeSet.isEmpty());

    List<Range<C>> asRanges = ImmutableList.copyOf(rangeSet.asRanges());

    // test that connected ranges are coalesced

    }

    @Override
    public boolean hasNext() {
      return !stack.isEmpty();
    }

    @Override
    public T next() {
      Iterator<T> itr = stack.getLast(); // throws NSEE if empty
      T result = checkNotNull(itr.next());
      if (!itr.hasNext()) {
        stack.removeLast();
      }
      Iterator<T> childItr = children(result).iterator();

        final LineIterator it = new LineIterator(reader);
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("aaa"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("bbb"));
        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is("ccc"));
        assertThat(it.hasNext(), is(not(true)));
    }

    /**
     * @throws Exception
     */
    @Test

        this.iterators = iterators;
    }

    @Override
    public boolean hasNext() {
        for (; index < iterators.length; ++index) {
            if (iterators[index].hasNext()) {
                return true;
            }
        }
        return false;
    }

    @Override
    public E next() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }

          int i;

          @Override
          public boolean hasNext() {
            return i < array.length;
          }

          @Override
          public String next() {
            if (!hasNext()) {
              throw new NoSuchElementException();
            }
            return array[i++];
          }
        };

    assertTrue(iterator.hasNext());
    assertEquals("a", iterator.next());
    try {

    assertEquals(rangeSet.asDescendingSetOfRanges().isEmpty(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asRanges().iterator().hasNext(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asDescendingSetOfRanges().iterator().hasNext(), rangeSet.isEmpty());

    List<Range<C>> asRanges = ImmutableList.copyOf(rangeSet.asRanges());

    // test that connected ranges are coalesced