@Override
  public int hashCode() {
    return getClass().hashCode()
        + (position == null ? 0 : position.hashCode())
        + (key == null ? 0 : key.hashCode())
        + (secondaryKey == null ? 0 : secondaryKey.hashCode())
        + (value == null ? 0 : value.hashCode());
  }
@Test
  public void equalsForEqualNullEntries() {
    ShuffleEntry entry0 = new ShuffleEntry(null, null, null);
    ShuffleEntry entry1 = new ShuffleEntry(null, null, null);

    assertEquals(entry0, entry1);
    assertEquals(entry1, entry0);
    assertEquals(entry0.hashCode(), entry1.hashCode());
  }