return LIST_ITEM;
        }

        @Override
        public boolean isNull() {
            return (size() == 0);
        }

        void normalize() {
            for (int i = size() - 1; i >= 0; i--) {
                Item lastItem = get(i);

                if (lastItem.isNull()) {
                    if (i == size() - 1 || get(i + 1).getType() == STRING_ITEM) {

        ImmutableSortedSet.copyOf(new String[] {"e", "e", "f", "b", "i", "d", "c", "k"});
    assertThat(set.floor("a")).isNull();
  }

  public void testCeiling_emptySet() {
    ImmutableSortedSet<String> set = ImmutableSortedSet.copyOf(new String[] {});
    assertThat(set.ceiling("f")).isNull();
  }

  public void testCeiling_elementPresent() {
    ImmutableSortedSet<String> set =

      T key = keysAndValues[i];
      T value = keysAndValues[i + 1];
      T old = map.put(key, value);
      assertWithMessage("Key %s set to %s and %s", key, value, old).that(old).isNull();
    }
    return map;
  }

  private static <T extends @Nullable Object> Entry<T, T> entry(T key, T value) {
    return new AbstractMap.SimpleImmutableEntry<>(key, value);
  }

      T key = keysAndValues[i];
      T value = keysAndValues[i + 1];
      T old = map.put(key, value);
      assertWithMessage("Key %s set to %s and %s", key, value, old).that(old).isNull();
    }
    return map;
  }

  private static <T extends @Nullable Object> Entry<T, T> entry(T key, T value) {
    return new AbstractMap.SimpleImmutableEntry<>(key, value);
  }