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

    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}
   *

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

  /**

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

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

    @Override
    public boolean contains(Object rowKey, Object columnKey) {
      assertTrue(Thread.holdsLock(mutex));

    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 Tables.unmodifiableTable(table).columnMap();
  }

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

  public void testColumnKeySet() {
    assertEquals(ImmutableSet.of(1), testTable.columnKeySet());
  }

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

  public void testRow() {
    assertEquals(ImmutableMap.of(), testTable.row('A'));
    assertEquals(ImmutableMap.of(1, "blah"), testTable.row('a'));
  }

  public void testRowKeySet() {

    Table<Integer, String, String> table = HashBasedTable.create();
    table.put(1, "foo", "apple");
    table.put(1, "bar", "banana");
    table.put(3, "foo", "cat");
    return Tables.transformValues(table, FIRST_CHARACTER).columnMap();
  }