return subSet(fromElement, true, toElement, false);
  }

  @Override
  public NavigableSet<E> headSet(@ParametricNullness E toElement, boolean inclusive) {
    return delegate().headSet(toElement, inclusive);
  }

  /**
   * A sensible definition of {@link #headSet(Object)} in terms of the {@link #headSet(Object,

  }

  @Override
  ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive) {
    return getSubSet(0, headIndex(toElement, inclusive));
  }

  int headIndex(E toElement, boolean inclusive) {
    int index = Collections.binarySearch(elements, checkNotNull(toElement), comparator());
    if (index >= 0) {
      return inclusive ? index + 1 : index;
    } else {
      return ~index;
    }
  }

  @Override
  public SortedSet<E> headSet(E toElement) {
    return headSet(toElement, false);
  }

  @Override
  public NavigableSet<E> headSet(E toElement, boolean inclusive) {
    return new SafeTreeSet<>(delegate.headSet(checkValid(toElement), inclusive));
  }

  @Override
  public @Nullable E higher(E e) {
    return delegate.higher(checkValid(e));
  }

  @Override
  public boolean isEmpty() {

      for (boolean inclusive : new boolean[] {false, true}) {
        assertThat(navigableMap.headMap(key, inclusive).entrySet())
            .containsExactlyElementsIn(expected.headMap(key, inclusive).entrySet())
            .inOrder();
        assertThat(navigableMap.tailMap(key, inclusive).entrySet())
            .containsExactlyElementsIn(expected.tailMap(key, inclusive).entrySet())
            .inOrder();

  @Override
  public SortedMap<K, V> headMap(K toKey) {
    return headMap(toKey, false);
  }

  @Override
  public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
    return new SafeTreeMap<>(delegate.headMap(checkValid(toKey), inclusive));
  }

  @Override
  public @Nullable Entry<K, V> higherEntry(K key) {
    return delegate.higherEntry(checkValid(key));
  }

  @Override

        : new EmptyContiguousSet<C>(domain);
  }

  @Override
  ContiguousSet<C> headSetImpl(C toElement, boolean inclusive) {
    return intersectionInCurrentDomain(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
  }

  @Override
  @SuppressWarnings("unchecked") // TODO(cpovirk): Use a shared unsafeCompare method.
  ContiguousSet<C> subSetImpl(

      for (List<Integer> contents : SAMPLE_INPUTS) {
        for (int i = 0; i < 10; i++) {
          for (boolean inclusive : ImmutableList.of(true, false)) {
            assertEquals(
                filter(createUnfiltered(contents).headSet(i, inclusive), EVEN),
                filter(createUnfiltered(contents), EVEN).headSet(i, inclusive));
          }
        }
      }
    }

    public void testNavigableTailSet() {

  /**
   * File Separator: These four information separators may be used within data in optional fashion,
   * except that their hierarchical relationship shall be: FS is the most inclusive, then GS, then
   * RS, and US is least inclusive. (The content and length of a File, Group, Record, or Unit are
   * not specified.)
   *
   * @since 8.0
   */
  public static final byte FS = 28;

  /**

  }

  @Override
  public NavigableMap<K, V> headMap(@ParametricNullness K toKey, boolean inclusive) {
    return delegate().headMap(toKey, inclusive);
  }

  @Override
  public NavigableMap<K, V> tailMap(@ParametricNullness K fromKey, boolean inclusive) {
    return delegate().tailMap(fromKey, inclusive);
  }

  /**
   * A sensible definition of {@link #headMap(Object)} in terms of {@link #headMap(Object,

  }

  @Override
  public NavigableMap<K, V> headMap(@ParametricNullness K toKey, boolean inclusive) {
    return delegate().headMap(toKey, inclusive);
  }

  @Override
  public NavigableMap<K, V> tailMap(@ParametricNullness K fromKey, boolean inclusive) {
    return delegate().tailMap(fromKey, inclusive);
  }

  /**
   * A sensible definition of {@link #headMap(Object)} in terms of {@link #headMap(Object,