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

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

    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));

  }

  @LazyInit @CheckForNull private transient ColumnMap columnMap;

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

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

    @Override

    checkNotNull(columnKey, "columnKey");
    return MoreObjects.firstNonNull(
        (ImmutableMap<R, V>) columnMap().get(columnKey), ImmutableMap.<R, V>of());
  }

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

  /**
   * {@inheritDoc}
   *

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

      table.put(1, "foo", 'a');
      table.put(1, "bar", 'b');
      table.put(3, "foo", 'c');
      return table.columnMap();
    }

    @Override
    protected Map<String, Map<Integer, Character>> makeEmptyMap() {
      return makeTable().columnMap();
    }
  }

      table.put(1, "foo", 'a');
      table.put(1, "bar", 'b');
      table.put(3, "foo", 'c');
      return table.columnMap();
    }

    @Override
    protected Map<String, Map<Integer, Character>> makeEmptyMap() {
      return makeTable().columnMap();
    }
  }

 * returns a {@link SortedMap}, instead of the {@link Set} and {@link Map} specified by the {@link
 * Table} interface.
 *
 * <p>The views returned by {@link #column}, {@link #columnKeySet()}, and {@link #columnMap()} have
 * iterators that don't support {@code remove()}. Otherwise, all optional operations are supported.
 * Null row keys, columns keys, and values are not supported.
 *

                  }
                }),
            mutex);
      }
    }

    @Override
    public Map<C, Map<R, V>> columnMap() {
      synchronized (mutex) {
        return map(
            transformValues(
                delegate().columnMap(),
                new com.google.common.base.Function<Map<R, V>, Map<R, V>>() {
                  @Override