ImmutableSortedSet.Builder<String> builder = ImmutableSortedSet.orderedBy(comparator);
      builder.add(BEFORE_FIRST);
      builder.add(elements);
      builder.add(AFTER_LAST);
      return builder.build().subSet(BEFORE_FIRST_2, AFTER_LAST).asList();
    }
  }

  @GwtIncompatible // NavigableSet
  public static class ImmutableSortedSetDescendingAsListGenerator extends TestStringListGenerator {
    @Override

      ImmutableSortedSet.Builder<String> builder = ImmutableSortedSet.orderedBy(comparator);
      builder.add(BEFORE_FIRST);
      builder.add(elements);
      builder.add(AFTER_LAST);
      return builder.build().subSet(BEFORE_FIRST_2, AFTER_LAST).asList();
    }
  }

  @GwtIncompatible // NavigableSet
  public static class ImmutableSortedSetDescendingAsListGenerator extends TestStringListGenerator {
    @Override

    public static final String BEFORE_FIRST = "\0";
    public static final String BEFORE_FIRST_2 = "\0\0";
    public static final String MIN_ELEMENT = "a";
    public static final String AFTER_LAST = "z";
    public static final String AFTER_LAST_2 = "zz";
  }

  public static class Chars extends SampleElements<Character> {
    public Chars() {

    public static final String BEFORE_FIRST = "\0";
    public static final String BEFORE_FIRST_2 = "\0\0";
    public static final String MIN_ELEMENT = "a";
    public static final String AFTER_LAST = "z";
    public static final String AFTER_LAST_2 = "zz";
  }

  public static class Chars extends SampleElements<Character> {
    public Chars() {