@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);

      return transformEntries(fromMap().headMap(toKey), transformer);
    }

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

    @Override
    public SortedMap<K, V2> subMap(@ParametricNullness K fromKey, @ParametricNullness K toKey) {

    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");

    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");

    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);

      synchronized (mutex) {
        return sortedMap(delegate().headMap(toKey), mutex);
      }
    }

    @Override
    public K lastKey() {
      synchronized (mutex) {
        return delegate().lastKey();
      }
    }

    @Override
    public SortedMap<K, V> subMap(K fromKey, K toKey) {
      synchronized (mutex) {

    removeFromReplica(replica, replicatedMinValue);
  }

  private static void removeMaxFromReplica(
      SortedMap<Integer, AtomicInteger> replica, int maxValue) {
    Integer replicatedMaxValue = replica.lastKey();
    assertTrue("maxValue is incorrect", replicatedMaxValue == maxValue);
    removeFromReplica(replica, replicatedMaxValue);
  }

    removeFromReplica(replica, replicatedMinValue);
  }

  private static void removeMaxFromReplica(
      SortedMap<Integer, AtomicInteger> replica, int maxValue) {
    Integer replicatedMaxValue = replica.lastKey();
    assertTrue("maxValue is incorrect", replicatedMaxValue == maxValue);
    removeFromReplica(replica, replicatedMaxValue);
  }

  @Override
  public Comparator<? super K> comparator() {
    return keySet().comparator();
  }

  @Override
  public K firstKey() {
    return keySet().first();
  }

  @Override
  public K lastKey() {
    return keySet().last();
  }

  private ImmutableSortedMap<K, V> getSubMap(int fromIndex, int toIndex) {
    if (fromIndex == 0 && toIndex == size()) {
      return this;