@Override
    public K firstKey() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().firstKey();
    }

    @Override
    public K lastKey() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().lastKey();
    }

    private static final long serialVersionUID = 0;
  }

  public static TestSuite suite() {
    TestSuite suite = new TestSuite();

      }
      return ((SortedMap<C, V>) backingRowMap).firstKey();
    }

    @Override
    public C lastKey() {
      updateBackingRowMapField();
      if (backingRowMap == null) {
        throw new NoSuchElementException();
      }
      return ((SortedMap<C, V>) backingRowMap).lastKey();
    }

    @CheckForNull transient SortedMap<C, V> wholeRow;

    @Override
    public K firstKey() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().firstKey();
    }

    @Override
    public K lastKey() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().lastKey();
    }

    private static final long serialVersionUID = 0;
  }

  public static TestSuite suite() {
    TestSuite suite = new TestSuite();

    return Iterables.<@Nullable Entry<K, V>>getFirst(descendingMap().entrySet(), null);
  }

  /**
   * A sensible definition of {@link #lastKey} in terms of {@code lastEntry}. If you override {@code
   * lastEntry}, you may wish to override {@code lastKey} to forward to this implementation.
   */
  protected K standardLastKey() {
    Entry<K, V> entry = lastEntry();
    if (entry == null) {

    return Iterables.<@Nullable Entry<K, V>>getFirst(descendingMap().entrySet(), null);
  }

  /**
   * A sensible definition of {@link #lastKey} in terms of {@code lastEntry}. If you override {@code
   * lastEntry}, you may wish to override {@code lastKey} to forward to this implementation.
   */
  protected K standardLastKey() {
    Entry<K, V> entry = lastEntry();
    if (entry == null) {

    return comparator;
  }

  @CheckForNull
  public K firstKey() {
    return sortedDelegate.firstKey();
  }

  @CheckForNull
  public K lastKey() {
    return sortedDelegate.lastKey();
  }

  @CheckForNull
  K higher(K k) {
    Iterator<K> iterator = keySet().tailSet(k).iterator();
    while (iterator.hasNext()) {
      K tmp = iterator.next();

    @Override
    @ParametricNullness
    public K firstKey() {
      return sortedMap().firstKey();
    }

    @Override
    @ParametricNullness
    public K lastKey() {
      return sortedMap().lastKey();
    }

    @Override
    public SortedMap<K, Collection<V>> headMap(@ParametricNullness K toKey) {
      return new SortedAsMap(sortedMap().headMap(toKey));
    }

    @Override
    @ParametricNullness
    public K firstKey() {
      return sortedMap().firstKey();
    }

    @Override
    @ParametricNullness
    public K lastKey() {
      return sortedMap().lastKey();
    }

    @Override
    public SortedMap<K, Collection<V>> headMap(@ParametricNullness K toKey) {
      return new SortedAsMap(sortedMap().headMap(toKey));
    }

    SortedMap<String, Collection<Integer>> asMap = multimap.asMap();
    assertEquals(Ordering.natural(), asMap.comparator());
    assertEquals("foo", asMap.firstKey());
    assertEquals("tree", asMap.lastKey());
    Set<Integer> fooValues = ImmutableSet.of(1, 3, 7);
    Set<Integer> googleValues = ImmutableSet.of(2, 6);
    Set<Integer> treeValues = ImmutableSet.of(4, 0);

    assertSame("bar", sortedTable.rowMap().firstKey());
  }

  public void testRowMapLastKey() {
    sortedTable = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    assertSame("foo", sortedTable.rowMap().lastKey());
  }

  public void testRowKeyMapHeadMap() {
    sortedTable = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    Map<String, Map<Integer, Character>> map = sortedTable.rowMap().headMap("cat");