Method removeOnlyNavigableSet

guava/src/com/google/common/collect/Maps.java:1165–1225

(
      NavigableSet<E> set)

  }

  @GwtIncompatible // NavigableSet
  private static <E extends @Nullable Object> NavigableSet<E> removeOnlyNavigableSet(
      NavigableSet<E> set) {
    return new ForwardingNavigableSet<E>() {
      @Override
      protected NavigableSet<E> delegate() {
        return set;
      }

      @Override
      public boolean add(@ParametricNullness E element) {
        throw new UnsupportedOperationException();
      }

      @Override
      public boolean addAll(Collection<? extends E> es) {
        throw new UnsupportedOperationException();
      }

      @Override
      public SortedSet<E> headSet(@ParametricNullness E toElement) {
        return removeOnlySortedSet(super.headSet(toElement));
      }

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

      @Override
      public SortedSet<E> subSet(
          @ParametricNullness E fromElement, @ParametricNullness E toElement) {
        return removeOnlySortedSet(super.subSet(fromElement, toElement));
      }

      @Override
      public NavigableSet<E> subSet(
          @ParametricNullness E fromElement,
          boolean fromInclusive,
          @ParametricNullness E toElement,
          boolean toInclusive) {
        return removeOnlyNavigableSet(
            super.subSet(fromElement, fromInclusive, toElement, toInclusive));
      }

      @Override
      public SortedSet<E> tailSet(@ParametricNullness E fromElement) {
        return removeOnlySortedSet(super.tailSet(fromElement));
      }

      @Override
      public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclusive) {
        return removeOnlyNavigableSet(super.tailSet(fromElement, inclusive));
      }

      @Override
      public NavigableSet<E> descendingSet() {
        return removeOnlyNavigableSet(super.descendingSet());