* collection in setUp(), but that caused problems when a tester changed the
   * value of set or collection but not both.
   */
  protected final Set<E> getSet() {
    return (Set<E>) collection;
  }

  private List<E> values;
  private @Nullable E a;
  private @Nullable E b;
  private @Nullable E c;

  @Override
  public void setUp() throws Exception {
    super.setUp();
    sortedSet = (SortedSet<E>) getSet();
    values =
        copyToList(
            getSubjectGenerator()
                .getSampleElements(getSubjectGenerator().getCollectionSize().getNumElements()));
    sort(values, sortedSet.comparator());

  private List<E> values;
  private E a;
  private E b;
  private E c;

  @Override
  public void setUp() throws Exception {
    super.setUp();
    navigableSet = (NavigableSet<E>) getSet();
    values =
        copyToList(
            getSubjectGenerator()
                .getSampleElements(getSubjectGenerator().getCollectionSize().getNumElements()));
    sort(values, navigableSet.comparator());

        for (O option : options) {
            Optional<T> o = getter.apply(option);
            if (o.isPresent()) {
                return o;
            }
        }
        return Optional.empty();
    }

    protected Optional<List<String>> collectListIfPresentOrEmpty(Function<O, Optional<List<String>>> getter) {
        int had = 0;

   */
  interface InternalEntry<K, V, E extends InternalEntry<K, V, E>> {
    /** Gets the next entry in the chain. */
    E getNext();

    /** Gets the entry's hash. */
    int getHash();

    /** Gets the key for this entry. */
    K getKey();

    /** Gets the value for the entry. */
    V getValue();
  }

  /*

  @Override
  public @Nullable Entry<K, V> firstEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(entryIterator(), null);
  }

  @Override
  public @Nullable Entry<K, V> lastEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(descendingEntryIterator(), null);
  }

  @Override
  public @Nullable Entry<K, V> pollFirstEntry() {

    @Override
    public @Nullable ReferenceEntry<Object, Object> getNext() {
      return null;
    }

    @Override
    public int getHash() {
      return 0;
    }

    @Override
    public @Nullable Object getKey() {
      return null;
    }

    @Override
    public long getAccessTime() {
      return 0;
    }

  @Override
  public @Nullable Entry<K, V> firstEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(entryIterator(), null);
  }

  @Override
  public @Nullable Entry<K, V> lastEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(descendingEntryIterator(), null);
  }

  @Override
  public @Nullable Entry<K, V> pollFirstEntry() {

          if (last == UNSET) {
            // we need to update the root link from table[]
            table[tableIndex] = getNext(entries[next]);
          } else {
            // we need to update the link from the chain
            entries[last] = swapNext(entries[last], getNext(entries[next]));
          }

          moveLastEntry(next);
          size--;
          modCount++;
          return oldValue;

      assertSame(keyOne, entryOne.getKey());
      assertEquals(hashOne, entryOne.getHash());
      assertThat(entryOne.getNext()).isNull();
      assertSame(valueOne, copyOne.getValue());

      InternalEntry<Object, Object, ?> copyTwo = segment.copyForTesting(entryTwo, copyOne);
      assertSame(keyTwo, copyTwo.getKey());
      assertEquals(hashTwo, copyTwo.getHash());