protected Set<String> create(String[] elements) {
                    Table<String, Integer, Character> table = HashBasedTable.create();
                    populateForRowKeySet(table, elements);
                    return table.rowKeySet();
                  }
                })
            .named("HashBasedTable.rowKeySet")
            .withFeatures(COLLECTION_FEATURES_REMOVE)

  }

  public void testEqualsObject() {
    new EqualsTester()
        .addEqualityGroup(testTable, HashBasedTable.create(testTable))
        .addEqualityGroup(ImmutableTable.of(), HashBasedTable.create())
        .addEqualityGroup(HashBasedTable.create(ImmutableTable.of('A', 2, "")))
        .testEquals();
  }

  @GwtIncompatible // ArrayTable
  public void testEqualsObjectNullValues() {

          return input == null ? null : input.charAt(0);
        }
      };

  @Override
  protected Table<String, Integer, Character> create(@Nullable Object... data) {
    Table<String, Integer, String> table = HashBasedTable.create();
    checkArgument(data.length % 3 == 0);
    for (int i = 0; i < data.length; i += 3) {
      String value = (data[i + 2] == null) ? null : (data[i + 2] + "transformed");

  public void testToTable() {
    Collector<Cell<String, String, Integer>, ?, Table<String, String, Integer>> collector =
        TableCollectors.toTable(
            Cell::getRowKey, Cell::getColumnKey, Cell::getValue, HashBasedTable::create);
    BiPredicate<Table<String, String, Integer>, Table<String, String, Integer>> equivalence =
        pairwiseOnResultOf(Table::cellSet);
    CollectorTester.of(collector, equivalence)
        .expectCollects(

  public void testEquals() {
    table = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    // We know that we have only added non-null Characters.
    Table<String, Integer, Character> hashCopy =
        HashBasedTable.create((Table<String, Integer, ? extends Character>) table);
    Table<String, Integer, C> reordered = create("foo", 3, 'c', "foo", 1, 'a', "bar", 1, 'b');

  }

  enum TableImpl {
    HashBasedTableImpl {
      @Override
      <R extends Comparable<R>, C extends Comparable<C>, V> Table<R, C, V> create(
          Table<R, C, V> contents) {
        return HashBasedTable.create(contents);
      }
    },
    TreeBasedTableImpl {
      @Override
      <R extends Comparable<R>, C extends Comparable<C>, V> Table<R, C, V> create(
          Table<R, C, V> contents) {

 * support {@link Iterator#remove}. If the table is modified after an iterator is created, the
 * iterator remains valid.
 *
 * <p>This class requires less memory than the {@link HashBasedTable} and {@link TreeBasedTable}
 * implementations, except when the table is sparse.
 *
 * <p>Null row keys or column keys are not permitted.
 *