collector = toImmutableTable(Cell::getRowKey, Cell::getColumnKey, t -> null);
      assertThrows(
          NullPointerException.class,
          () -> Stream.of(immutableCell("one", "uno", 1)).collect(collector));
    }
    {
      Collector<Cell<String, String, Integer>, ?, ImmutableTable<String, String, Integer>>
          collector = toImmutableTable(Cell::getRowKey, Cell::getColumnKey, Cell::getValue);
      assertThrows(

        Cell<?, ?, ?> other = (Cell<?, ?, ?>) obj;
        return Objects.equals(getRowKey(), other.getRowKey())
            && Objects.equals(getColumnKey(), other.getColumnKey())
            && Objects.equals(getValue(), other.getValue());
      }
      return false;
    }

    @Override
    public int hashCode() {
      return Objects.hash(getRowKey(), getColumnKey(), getValue());
    }

    @Override

                      @SuppressWarnings("unchecked")
                      Cell<String, Integer, Character> cell =
                          (Cell<String, Integer, Character>) element;
                      table.put(cell.getRowKey(), cell.getColumnKey(), cell.getValue());
                    }
                    return table.cellSet();
                  }

                  @Override

   * @since 7.0
   */
  interface Cell<
      R extends @Nullable Object, C extends @Nullable Object, V extends @Nullable Object> {
    /** Returns the row key of this cell. */
    @ParametricNullness
    R getRowKey();

    /** Returns the column key of this cell. */
    @ParametricNullness
    C getColumnKey();

    /** Returns the value of this cell. */
    @ParametricNullness
    V getValue();

    /**

        checkNotNull(cell.getRowKey(), "row");
        checkNotNull(cell.getColumnKey(), "column");
        checkNotNull(cell.getValue(), "value");
        @SuppressWarnings("unchecked") // all supported methods are covariant
        Cell<R, C, V> immutableCell = (Cell<R, C, V>) cell;
        cells.add(immutableCell);
      } else {
        put(cell.getRowKey(), cell.getColumnKey(), cell.getValue());
      }

        checkNotNull(cell.getRowKey(), "row");
        checkNotNull(cell.getColumnKey(), "column");
        checkNotNull(cell.getValue(), "value");
        @SuppressWarnings("unchecked") // all supported methods are covariant
        Cell<R, C, V> immutableCell = (Cell<R, C, V>) cell;
        cells.add(immutableCell);
      } else {
        put(cell.getRowKey(), cell.getColumnKey(), cell.getValue());
      }

  }

  public void testHashing() throws Exception {
    for (String stringToTest : INPUTS) {
      for (Table.Cell<String, SecretKey, HashFunction> cell : ALGORITHMS.cellSet()) {
        String algorithm = cell.getRowKey();
        SecretKey key = cell.getColumnKey();
        HashFunction hashFunc = cell.getValue();
        assertMacHashing(HashTestUtils.ascii(stringToTest), algorithm, key, hashFunc);
      }
    }
  }

      }
    }
  }

  public void testKnownUtf8Hashing() {
    for (Cell<HashFunction, String, String> cell : KNOWN_HASHES.cellSet()) {
      HashFunction func = cell.getRowKey();
      String input = cell.getColumnKey();
      String expected = cell.getValue();
      assertEquals(
          String.format(Locale.ROOT, "Known hash for hash(%s, UTF_8) failed", input),
          expected,

      }
    }
  }

  public void testKnownUtf8Hashing() {
    for (Cell<HashFunction, String, String> cell : KNOWN_HASHES.cellSet()) {
      HashFunction func = cell.getRowKey();
      String input = cell.getColumnKey();
      String expected = cell.getValue();
      assertEquals(
          String.format(Locale.ROOT, "Known hash for hash(%s, UTF_8) failed", input),
          expected,

    return new Tables.AbstractCell<R, C, @Nullable V>() {
      final int rowIndex = index / columnList.size();
      final int columnIndex = index % columnList.size();

      @Override
      public R getRowKey() {
        return rowList.get(rowIndex);
      }

      @Override
      public C getColumnKey() {
        return columnList.get(columnIndex);
      }

      @Override