TreeBasedTable<String, Integer, Character> table = makeTable();
    populateTable(table);
    return table.rowMap().subMap("b", "x");
  }

  @Override
  protected Map<String, Map<Integer, Character>> makeEmptyMap() {
    return makeTable().rowMap().subMap("b", "x");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "z";
  }

  @Override
  public boolean containsRow(@CheckForNull Object rowKey) {
    return Maps.safeContainsKey(rowMap(), rowKey);
  }

  @Override
  public boolean containsColumn(@CheckForNull Object columnKey) {
    return Maps.safeContainsKey(columnMap(), columnKey);
  }

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

  @Override
  public Set<C> columnKeySet() {
    return columnMap().keySet();

      return super.put(key, value);
    }
  }

  // rowKeySet() and rowMap() are defined here so they appear in the Javadoc.

  @Override
  public SortedSet<R> rowKeySet() {
    return super.rowKeySet();
  }

  @Override
  public SortedMap<R, Map<C, V>> rowMap() {
    return super.rowMap();
  }

  /** Overridden column iterator to return columns values in globally sorted order. */

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Interface that extends {@code Table} and whose rows are sorted.
 *
 * <p>The {@link #rowKeySet} method returns a {@link SortedSet} and the {@link #rowMap} method
 * returns a {@link SortedMap}, instead of the {@link Set} and {@link Map} specified by the {@link
 * Table} interface.
 *
 * @author Warren Dukes
 * @since 8.0
 */
@GwtCompatible

  }

  @LazyInit @CheckForNull private transient RowMap rowMap;

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

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

    @Override

    return delegate().row(rowKey);
  }

  @Override
  public Set<R> rowKeySet() {
    return delegate().rowKeySet();
  }

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

  @Override
  public int size() {
    return delegate().size();
  }

  @Override
  public Collection<V> values() {
    return delegate().values();
  }

    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) {

    original.put(1, "foo", 'a');
    assertSame(original.columnKeySet(), transpose.rowKeySet());
    assertSame(original.rowKeySet(), transpose.columnKeySet());
    assertSame(original.columnMap(), transpose.rowMap());
    assertSame(original.rowMap(), transpose.columnMap());
    assertSame(original.values(), transpose.values());
    assertEquals(original.row(1), transpose.column(1));
    assertEquals(original.row(2), transpose.column(2));

    }

    @Override
    public Map<R, Map<C, V2>> rowMap() {
      Function<Map<C, V1>, Map<C, V2>> rowFunction =
          new Function<Map<C, V1>, Map<C, V2>>() {
            @Override
            public Map<C, V2> apply(Map<C, V1> row) {
              return Maps.transformValues(row, function);
            }
          };
      return Maps.transformValues(fromTable.rowMap(), rowFunction);
    }

    @Override