}

  @LazyInit private transient @Nullable RowMap rowMap;

  @Override
  public Map<R, Map<C, @Nullable V>> rowMap() {
    RowMap map = rowMap;
    return (map == null) ? rowMap = new RowMap() : map;
  }

  @WeakOuter
  private final class RowMap extends ArrayMap<R, Map<C, @Nullable V>> {
    private RowMap() {
      super(rowKeyToIndex);
    }

    @Override

    public Set<R> rowKeySet() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.rowKeySet();
    }

    @Override
    public Map<R, Map<C, V>> rowMap() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.rowMap();
    }

    private static final long serialVersionUID = 0;
  }

  @Override
  protected Table<String, Integer, Character> create(@Nullable Object... data) {

    public Set<R> rowKeySet() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.rowKeySet();
    }

    @Override
    public Map<R, Map<C, V>> rowMap() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.rowMap();
    }

    private static final long serialVersionUID = 0;
  }

  @Override
  protected Table<String, Integer, Character> create(@Nullable Object... data) {

    RowSortedTable<String, Integer, Character> table = TreeBasedTable.create();
    table.put("foo", 1, 'a');
    table.put("bar", 1, 'b');
    table.put("foo", 3, 'c');
    return unmodifiableRowSortedTable(table).rowMap();
  }

  @Override
  public ImmutableMap<C, Map<R, V>> columnMap() {
    return ImmutableMap.of(singleColumnKey, (Map<R, V>) ImmutableMap.of(singleRowKey, singleValue));
  }

  @Override
  public ImmutableMap<R, Map<C, V>> rowMap() {
    return ImmutableMap.of(singleRowKey, (Map<C, V>) ImmutableMap.of(singleColumnKey, singleValue));
  }

  @Override
  public int size() {
    return 1;
  }

  @Override

   */
  @Override
  public ImmutableMap<C, V> row(R rowKey) {
    checkNotNull(rowKey, "rowKey");
    return MoreObjects.firstNonNull((ImmutableMap<C, V>) rowMap().get(rowKey), ImmutableMap.of());
  }

  @Override
  public ImmutableSet<R> rowKeySet() {
    return rowMap().keySet();
  }

  /**
   * {@inheritDoc}
   *
   * <p>The value {@code Map<C, V>} instances in the returned map are {@link ImmutableMap} instances

    Table<String, Integer, Character> table = HashBasedTable.create();
    table.put("foo", 1, 'a');
    table.put("bar", 1, 'b');
    table.put("foo", 3, 'c');
    return unmodifiableTable(table).rowMap();
  }

    table.put("foo", 1, "apple");
    table.put("bar", 1, "banana");
    table.put("foo", 3, "cat");
    return transformValues(table, TableCollectionTest.FIRST_CHARACTER).rowMap();
  }

   */
  @Override
  public ImmutableMap<C, V> row(R rowKey) {
    checkNotNull(rowKey, "rowKey");
    return MoreObjects.firstNonNull((ImmutableMap<C, V>) rowMap().get(rowKey), ImmutableMap.of());
  }

  @Override
  public ImmutableSet<R> rowKeySet() {
    return rowMap().keySet();
  }

  /**
   * {@inheritDoc}
   *
   * <p>The value {@code Map<C, V>} instances in the returned map are {@link ImmutableMap} instances

  }

  public void testRowKeySet() {
    assertEquals(ImmutableSet.of('a'), testTable.rowKeySet());
  }

  public void testRowMap() {
    assertEquals(ImmutableMap.of('a', ImmutableMap.of(1, "blah")), testTable.rowMap());
  }

  public void testEqualsObject() {
    new EqualsTester()
        .addEqualityGroup(testTable, HashBasedTable.create(testTable))
        .addEqualityGroup(ImmutableTable.of(), HashBasedTable.create())