* Null row keys, columns keys, and values are not supported.
 *
 * <p>Lookups by row key are often faster than lookups by column key, because the data is stored in
 * a {@code Map<R, Map<C, V>>}. A method call like {@code column(columnKey).get(rowKey)} still runs
 * quickly, since the row key is provided. However, {@code column(columnKey).size()} takes longer,
 * since an iteration across all row keys occurs.
 *

 * order of the various views.
 *
 * <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.
 *
 * <p>Lookups by row key are often faster than lookups by column key, because the data is stored in

   * generated by applying the specified functions. If multiple inputs are mapped to the same row
   * and column pair, they will be combined with the specified merging function in encounter order.
   *
   * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
   * if the row, column, value, or merging functions return null on any input.
   *

    }
  }

  public void testColumnMissing() {
    table = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    Map<String, Character> column = table.column(4);
    assertTrue(column.isEmpty());
    try {
      column.put("foo", 'd');
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  public void testRowPutIllegal() {

    }
  }

  public void testColumnMissing() {
    table = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    Map<String, Character> column = table.column(4);
    assertTrue(column.isEmpty());
    try {
      column.put("foo", 'd');
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  public void testRowPutIllegal() {

    assertSame(original.values(), transpose.values());
    assertEquals(original.row(1), transpose.column(1));
    assertEquals(original.row(2), transpose.column(2));
    assertEquals(original.column("foo"), transpose.row("foo"));
    assertEquals(original.column("bar"), transpose.row("bar"));
  }

        .containsExactly("cat", "axe", "baz", "tub", "dog", "bar", "foo", "foo", "bar")
        .inOrder();
    assertThat(table.row('c').keySet()).containsExactly(0, 3).inOrder();
    assertThat(table.column(5).keySet()).containsExactly('e', 'x').inOrder();
  }

  public void testBuilder_orderRowsAndColumnsBy_dense() {
    ImmutableTable.Builder<Character, Integer, String> builder = ImmutableTable.builder();

 * order of the various views.
 *
 * <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.
 *
 * <p>Lookups by row key are often faster than lookups by column key, because the data is stored in

  private static final class MutableCell<R, C, V> extends AbstractCell<R, C, V> {
    private final R row;
    private final C column;
    private V value;

    MutableCell(R row, C column, V value) {
      this.row = checkNotNull(row, "row");
      this.column = checkNotNull(column, "column");
      this.value = checkNotNull(value, "value");
    }

    @Override
    public R getRowKey() {
      return row;

      table.put(row, 2, 'b');
    }
  }

  private static void populateForColumnKeySet(
      Table<Integer, String, Character> table, String[] elements) {
    for (String column : elements) {
      table.put(1, column, 'a');
      table.put(2, column, 'b');
    }
  }

  private static void populateForValues(
      Table<Integer, Character, String> table, String[] elements) {
    for (int i = 0; i < elements.length; i++) {