@Override
  public int hashCode() {
    return Arrays.hashCode(_values);
  }
@Test
  public void testPrimaryKeyComparison() {
    PrimaryKey left = new PrimaryKey(new Object[]{"111", 2});
    PrimaryKey right = new PrimaryKey(new Object[]{"111", 2});
    assertEquals(left, right);
    assertEquals(left.hashCode(), right.hashCode());

    right = new PrimaryKey(new Object[]{"222", 2});
    assertNotEquals(left, right);
    assertNotEquals(left.hashCode(), right.hashCode());
  }