Exemplo n.º 1
0
 /**
  * Returns an immutable sorted set containing the elements of a sorted set, sorted by the same
  * {@code Comparator}. That behavior differs from {@link #copyOf(Iterable)}, which always uses the
  * natural ordering of the elements.
  *
  * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
  * safe to do so. The exact circumstances under which a copy will or will not be performed are
  * undocumented and subject to change.
  *
  * <p>This method is safe to use even when {@code sortedSet} is a synchronized or concurrent
  * collection that is currently being modified by another thread.
  *
  * @throws NullPointerException if {@code sortedSet} or any of its elements is null
  */
 public static <E> ImmutableSortedSet<E> copyOfSorted(SortedSet<E> sortedSet) {
   Comparator<? super E> comparator = SortedIterables.comparator(sortedSet);
   ImmutableList<E> list = ImmutableList.copyOf(sortedSet);
   if (list.isEmpty()) {
     return emptySet(comparator);
   } else {
     return new RegularImmutableSortedSet<E>(list, comparator);
   }
 }
Exemplo n.º 2
0
 /**
  * Combines four iterables into a single iterable. The returned iterable has an iterator that
  * traverses the elements in {@code a}, followed by the elements in {@code b}, followed by the
  * elements in {@code c}, followed by the elements in {@code d}. The source iterators are not
  * polled until necessary.
  *
  * <p>The returned iterable's iterator supports {@code remove()} when the corresponding input
  * iterator supports it.
  */
 public static <T> Iterable<T> concat(
     Iterable<? extends T> a,
     Iterable<? extends T> b,
     Iterable<? extends T> c,
     Iterable<? extends T> d) {
   return concat(ImmutableList.of(a, b, c, d));
 }
Exemplo n.º 3
0
 static <E> RegularImmutableSortedSet<E> emptySet(Comparator<? super E> comparator) {
   if (NATURAL_ORDER.equals(comparator)) {
     return (RegularImmutableSortedSet<E>) NATURAL_EMPTY_SET;
   } else {
     return new RegularImmutableSortedSet<E>(ImmutableList.<E>of(), comparator);
   }
 }
Exemplo n.º 4
0
 /**
  * Constructs an {@code ImmutableSortedSet} from the first {@code n} elements of {@code contents}.
  * If {@code k} is the size of the returned {@code ImmutableSortedSet}, then the sorted unique
  * elements are in the first {@code k} positions of {@code contents}, and {@code contents[i] ==
  * null} for {@code k <= i < n}.
  *
  * <p>If {@code k == contents.length}, then {@code contents} may no longer be safe for
  * modification.
  *
  * @throws NullPointerException if any of the first {@code n} elements of {@code contents} is null
  */
 static <E> ImmutableSortedSet<E> construct(
     Comparator<? super E> comparator, int n, E... contents) {
   if (n == 0) {
     return emptySet(comparator);
   }
   checkElementsNotNull(contents, n);
   Arrays.sort(contents, 0, n, comparator);
   int uniques = 1;
   for (int i = 1; i < n; i++) {
     E cur = contents[i];
     E prev = contents[uniques - 1];
     if (comparator.compare(cur, prev) != 0) {
       contents[uniques++] = cur;
     }
   }
   Arrays.fill(contents, uniques, n, null);
   return new RegularImmutableSortedSet<E>(
       ImmutableList.<E>asImmutableList(contents, uniques), comparator);
 }
Exemplo n.º 5
0
 @Override
 public ImmutableList<E> subList(int fromIndex, int toIndex) {
   Preconditions.checkPositionIndexes(fromIndex, toIndex, 1);
   return (fromIndex == toIndex) ? ImmutableList.<E>of() : this;
 }
Exemplo n.º 6
0
 /**
  * Combines multiple iterables into a single iterable. The returned iterable has an iterator that
  * traverses the elements of each iterable in {@code inputs}. The input iterators are not polled
  * until necessary.
  *
  * <p>The returned iterable's iterator supports {@code remove()} when the corresponding input
  * iterator supports it.
  *
  * @throws NullPointerException if any of the provided iterables is null
  */
 public static <T> Iterable<T> concat(Iterable<? extends T>... inputs) {
   return concat(ImmutableList.copyOf(inputs));
 }
Exemplo n.º 7
0
 /** Returns an immutable sorted set containing a single element. */
 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E element) {
   return new RegularImmutableSortedSet<E>(ImmutableList.of(element), Ordering.natural());
 }
Exemplo n.º 8
0
// TODO(benyu): benchmark and optimize all creation paths, which are a mess now
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableSortedSet<E> extends ImmutableSortedSetFauxverideShim<E>
    implements NavigableSet<E>, SortedIterable<E> {

  private static final Comparator<Comparable> NATURAL_ORDER = Ordering.natural();

  private static final RegularImmutableSortedSet<Comparable> NATURAL_EMPTY_SET =
      new RegularImmutableSortedSet<Comparable>(ImmutableList.<Comparable>of(), NATURAL_ORDER);

  static <E> RegularImmutableSortedSet<E> emptySet(Comparator<? super E> comparator) {
    if (NATURAL_ORDER.equals(comparator)) {
      return (RegularImmutableSortedSet<E>) NATURAL_EMPTY_SET;
    } else {
      return new RegularImmutableSortedSet<E>(ImmutableList.<E>of(), comparator);
    }
  }

  /** Returns the empty immutable sorted set. */
  public static <E> ImmutableSortedSet<E> of() {
    return (ImmutableSortedSet<E>) NATURAL_EMPTY_SET;
  }

  /** Returns an immutable sorted set containing a single element. */
  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E element) {
    return new RegularImmutableSortedSet<E>(ImmutableList.of(element), Ordering.natural());
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
   * one specified is included.
   *
   * @throws NullPointerException if any element is null
   */
  @SuppressWarnings("unchecked")
  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E e1, E e2) {
    return construct(Ordering.natural(), 2, e1, e2);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
   * one specified is included.
   *
   * @throws NullPointerException if any element is null
   */
  @SuppressWarnings("unchecked")
  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E e1, E e2, E e3) {
    return construct(Ordering.natural(), 3, e1, e2, e3);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
   * one specified is included.
   *
   * @throws NullPointerException if any element is null
   */
  @SuppressWarnings("unchecked")
  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E e1, E e2, E e3, E e4) {
    return construct(Ordering.natural(), 4, e1, e2, e3, e4);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
   * one specified is included.
   *
   * @throws NullPointerException if any element is null
   */
  @SuppressWarnings("unchecked")
  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
      E e1, E e2, E e3, E e4, E e5) {
    return construct(Ordering.natural(), 5, e1, e2, e3, e4, e5);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
   * one specified is included.
   *
   * @throws NullPointerException if any element is null
   * @since 3.0 (source-compatible since 2.0)
   */
  @SuppressWarnings("unchecked")
  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
      E e1, E e2, E e3, E e4, E e5, E e6, E... remaining) {
    Comparable[] contents = new Comparable[6 + remaining.length];
    contents[0] = e1;
    contents[1] = e2;
    contents[2] = e3;
    contents[3] = e4;
    contents[4] = e5;
    contents[5] = e6;
    System.arraycopy(remaining, 0, contents, 6, remaining.length);
    return construct(Ordering.natural(), contents.length, (E[]) contents);
  }

  // TODO(kevinb): Consider factory methods that reject duplicates

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
   * one specified is included.
   *
   * @throws NullPointerException if any of {@code elements} is null
   * @since 3.0
   */
  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> copyOf(E[] elements) {
    return construct(Ordering.natural(), elements.length, elements.clone());
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@code compareTo()}, only the first one
   * specified is included. To create a copy of a {@code SortedSet} that preserves the comparator,
   * call {@link #copyOfSorted} instead. This method iterates over {@code elements} at most once.
   *
   * <p>Note that if {@code s} is a {@code Set<String>}, then {@code ImmutableSortedSet.copyOf(s)}
   * returns an {@code ImmutableSortedSet<String>} containing each of the strings in {@code s},
   * while {@code ImmutableSortedSet.of(s)} returns an {@code ImmutableSortedSet<Set<String>>}
   * containing one element (the given set itself).
   *
   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * <p>This method is not type-safe, as it may be called on elements that are not mutually
   * comparable.
   *
   * @throws ClassCastException if the elements are not mutually comparable
   * @throws NullPointerException if any of {@code elements} is null
   */
  public static <E> ImmutableSortedSet<E> copyOf(Iterable<? extends E> elements) {
    // Hack around E not being a subtype of Comparable.
    // Unsafe, see ImmutableSortedSetFauxverideShim.
    @SuppressWarnings("unchecked")
    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable>natural();
    return copyOf(naturalOrder, elements);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@code compareTo()}, only the first one
   * specified is included. To create a copy of a {@code SortedSet} that preserves the comparator,
   * call {@link #copyOfSorted} instead. This method iterates over {@code elements} at most once.
   *
   * <p>Note that if {@code s} is a {@code Set<String>}, then {@code ImmutableSortedSet.copyOf(s)}
   * returns an {@code ImmutableSortedSet<String>} containing each of the strings in {@code s},
   * while {@code ImmutableSortedSet.of(s)} returns an {@code ImmutableSortedSet<Set<String>>}
   * containing one element (the given set itself).
   *
   * <p><b>Note:</b> Despite what the method name suggests, if {@code elements} is an {@code
   * ImmutableSortedSet}, it may be returned instead of a copy.
   *
   * <p>This method is not type-safe, as it may be called on elements that are not mutually
   * comparable.
   *
   * <p>This method is safe to use even when {@code elements} is a synchronized or concurrent
   * collection that is currently being modified by another thread.
   *
   * @throws ClassCastException if the elements are not mutually comparable
   * @throws NullPointerException if any of {@code elements} is null
   * @since 7.0 (source-compatible since 2.0)
   */
  public static <E> ImmutableSortedSet<E> copyOf(Collection<? extends E> elements) {
    // Hack around E not being a subtype of Comparable.
    // Unsafe, see ImmutableSortedSetFauxverideShim.
    @SuppressWarnings("unchecked")
    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable>natural();
    return copyOf(naturalOrder, elements);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
   * When multiple elements are equivalent according to {@code compareTo()}, only the first one
   * specified is included.
   *
   * <p>This method is not type-safe, as it may be called on elements that are not mutually
   * comparable.
   *
   * @throws ClassCastException if the elements are not mutually comparable
   * @throws NullPointerException if any of {@code elements} is null
   */
  public static <E> ImmutableSortedSet<E> copyOf(Iterator<? extends E> elements) {
    // Hack around E not being a subtype of Comparable.
    // Unsafe, see ImmutableSortedSetFauxverideShim.
    @SuppressWarnings("unchecked")
    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable>natural();
    return copyOf(naturalOrder, elements);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by the given {@code
   * Comparator}. When multiple elements are equivalent according to {@code compareTo()}, only the
   * first one specified is included.
   *
   * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
   */
  public static <E> ImmutableSortedSet<E> copyOf(
      Comparator<? super E> comparator, Iterator<? extends E> elements) {
    return new Builder<E>(comparator).addAll(elements).build();
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by the given {@code
   * Comparator}. When multiple elements are equivalent according to {@code compare()}, only the
   * first one specified is included. This method iterates over {@code elements} at most once.
   *
   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
   */
  public static <E> ImmutableSortedSet<E> copyOf(
      Comparator<? super E> comparator, Iterable<? extends E> elements) {
    checkNotNull(comparator);
    boolean hasSameComparator = SortedIterables.hasSameComparator(comparator, elements);

    if (hasSameComparator && (elements instanceof ImmutableSortedSet)) {
      @SuppressWarnings("unchecked")
      ImmutableSortedSet<E> original = (ImmutableSortedSet<E>) elements;
      if (!original.isPartialView()) {
        return original;
      }
    }
    @SuppressWarnings("unchecked") // elements only contains E's; it's safe.
    E[] array = (E[]) Iterables.toArray(elements);
    return construct(comparator, array.length, array);
  }

  /**
   * Returns an immutable sorted set containing the given elements sorted by the given {@code
   * Comparator}. When multiple elements are equivalent according to {@code compareTo()}, only the
   * first one specified is included.
   *
   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * <p>This method is safe to use even when {@code elements} is a synchronized or concurrent
   * collection that is currently being modified by another thread.
   *
   * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
   * @since 7.0 (source-compatible since 2.0)
   */
  public static <E> ImmutableSortedSet<E> copyOf(
      Comparator<? super E> comparator, Collection<? extends E> elements) {
    return copyOf(comparator, (Iterable<? extends E>) elements);
  }

  /**
   * Returns an immutable sorted set containing the elements of a sorted set, sorted by the same
   * {@code Comparator}. That behavior differs from {@link #copyOf(Iterable)}, which always uses the
   * natural ordering of the elements.
   *
   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * <p>This method is safe to use even when {@code sortedSet} is a synchronized or concurrent
   * collection that is currently being modified by another thread.
   *
   * @throws NullPointerException if {@code sortedSet} or any of its elements is null
   */
  public static <E> ImmutableSortedSet<E> copyOfSorted(SortedSet<E> sortedSet) {
    Comparator<? super E> comparator = SortedIterables.comparator(sortedSet);
    ImmutableList<E> list = ImmutableList.copyOf(sortedSet);
    if (list.isEmpty()) {
      return emptySet(comparator);
    } else {
      return new RegularImmutableSortedSet<E>(list, comparator);
    }
  }

  /**
   * Constructs an {@code ImmutableSortedSet} from the first {@code n} elements of {@code contents}.
   * If {@code k} is the size of the returned {@code ImmutableSortedSet}, then the sorted unique
   * elements are in the first {@code k} positions of {@code contents}, and {@code contents[i] ==
   * null} for {@code k <= i < n}.
   *
   * <p>If {@code k == contents.length}, then {@code contents} may no longer be safe for
   * modification.
   *
   * @throws NullPointerException if any of the first {@code n} elements of {@code contents} is null
   */
  static <E> ImmutableSortedSet<E> construct(
      Comparator<? super E> comparator, int n, E... contents) {
    if (n == 0) {
      return emptySet(comparator);
    }
    checkElementsNotNull(contents, n);
    Arrays.sort(contents, 0, n, comparator);
    int uniques = 1;
    for (int i = 1; i < n; i++) {
      E cur = contents[i];
      E prev = contents[uniques - 1];
      if (comparator.compare(cur, prev) != 0) {
        contents[uniques++] = cur;
      }
    }
    Arrays.fill(contents, uniques, n, null);
    return new RegularImmutableSortedSet<E>(
        ImmutableList.<E>asImmutableList(contents, uniques), comparator);
  }

  /**
   * Returns a builder that creates immutable sorted sets with an explicit comparator. If the
   * comparator has a more general type than the set being generated, such as creating a {@code
   * SortedSet<Integer>} with a {@code Comparator<Number>}, use the {@link Builder} constructor
   * instead.
   *
   * @throws NullPointerException if {@code comparator} is null
   */
  public static <E> Builder<E> orderedBy(Comparator<E> comparator) {
    return new Builder<E>(comparator);
  }

  /**
   * Returns a builder that creates immutable sorted sets whose elements are ordered by the reverse
   * of their natural ordering.
   */
  public static <E extends Comparable<?>> Builder<E> reverseOrder() {
    return new Builder<E>(Ordering.natural().reverse());
  }

  /**
   * Returns a builder that creates immutable sorted sets whose elements are ordered by their
   * natural ordering. The sorted sets use {@link Ordering#natural()} as the comparator. This method
   * provides more type-safety than {@link #builder}, as it can be called only for classes that
   * implement {@link Comparable}.
   */
  public static <E extends Comparable<?>> Builder<E> naturalOrder() {
    return new Builder<E>(Ordering.natural());
  }

  /**
   * A builder for creating immutable sorted set instances, especially {@code public static final}
   * sets ("constant sets"), with a given comparator. Example:
   *
   * <pre>{@code
   * public static final ImmutableSortedSet<Number> LUCKY_NUMBERS =
   *     new ImmutableSortedSet.Builder<Number>(ODDS_FIRST_COMPARATOR)
   *         .addAll(SINGLE_DIGIT_PRIMES)
   *         .add(42)
   *         .build();
   * }</pre>
   *
   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
   * multiple sets in series. Each set is a superset of the set created before it.
   *
   * @since 2.0
   */
  public static final class Builder<E> extends ImmutableSet.Builder<E> {
    private final Comparator<? super E> comparator;

    /**
     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
     * ImmutableSortedSet#orderedBy}.
     */
    public Builder(Comparator<? super E> comparator) {
      this.comparator = checkNotNull(comparator);
    }

    /**
     * Adds {@code element} to the {@code ImmutableSortedSet}. If the {@code ImmutableSortedSet}
     * already contains {@code element}, then {@code add} has no effect. (only the previously added
     * element is retained).
     *
     * @param element the element to add
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code element} is null
     */
    @Override
    public Builder<E> add(E element) {
      super.add(element);
      return this;
    }

    /**
     * Adds each element of {@code elements} to the {@code ImmutableSortedSet}, ignoring duplicate
     * elements (only the first duplicate element is added).
     *
     * @param elements the elements to add
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code elements} contains a null element
     */
    @Override
    public Builder<E> add(E... elements) {
      super.add(elements);
      return this;
    }

    /**
     * Adds each element of {@code elements} to the {@code ImmutableSortedSet}, ignoring duplicate
     * elements (only the first duplicate element is added).
     *
     * @param elements the elements to add to the {@code ImmutableSortedSet}
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code elements} contains a null element
     */
    @Override
    public Builder<E> addAll(Iterable<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    /**
     * Adds each element of {@code elements} to the {@code ImmutableSortedSet}, ignoring duplicate
     * elements (only the first duplicate element is added).
     *
     * @param elements the elements to add to the {@code ImmutableSortedSet}
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code elements} contains a null element
     */
    @Override
    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableSortedSet} based on the contents of the {@code
     * Builder} and its comparator.
     */
    @Override
    public ImmutableSortedSet<E> build() {
      @SuppressWarnings("unchecked") // we're careful to put only E's in here
      E[] contentsArray = (E[]) contents;
      ImmutableSortedSet<E> result = construct(comparator, size, contentsArray);
      this.size = result.size(); // we eliminated duplicates in-place in contentsArray
      return result;
    }
  }

  int unsafeCompare(Object a, Object b) {
    return unsafeCompare(comparator, a, b);
  }

  static int unsafeCompare(Comparator<?> comparator, Object a, Object b) {
    // Pretend the comparator can compare anything. If it turns out it can't
    // compare a and b, we should get a CCE on the subsequent line. Only methods
    // that are spec'd to throw CCE should call this.
    @SuppressWarnings("unchecked")
    Comparator<Object> unsafeComparator = (Comparator<Object>) comparator;
    return unsafeComparator.compare(a, b);
  }

  final transient Comparator<? super E> comparator;

  ImmutableSortedSet(Comparator<? super E> comparator) {
    this.comparator = comparator;
  }

  /**
   * Returns the comparator that orders the elements, which is {@link Ordering#natural()} when the
   * natural ordering of the elements is used. Note that its behavior is not consistent with {@link
   * SortedSet#comparator()}, which returns {@code null} to indicate natural ordering.
   */
  @Override
  public Comparator<? super E> comparator() {
    return comparator;
  }

  @Override // needed to unify the iterator() methods in Collection and SortedIterable
  public abstract UnmodifiableIterator<E> iterator();

  /**
   * {@inheritDoc}
   *
   * <p>This method returns a serializable {@code ImmutableSortedSet}.
   *
   * <p>The {@link SortedSet#headSet} documentation states that a subset of a subset throws an
   * {@link IllegalArgumentException} if passed a {@code toElement} greater than an earlier {@code
   * toElement}. However, this method doesn't throw an exception in that situation, but instead
   * keeps the original {@code toElement}.
   */
  @Override
  public ImmutableSortedSet<E> headSet(E toElement) {
    return headSet(toElement, false);
  }

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public ImmutableSortedSet<E> headSet(E toElement, boolean inclusive) {
    return headSetImpl(checkNotNull(toElement), inclusive);
  }

  /**
   * {@inheritDoc}
   *
   * <p>This method returns a serializable {@code ImmutableSortedSet}.
   *
   * <p>The {@link SortedSet#subSet} documentation states that a subset of a subset throws an {@link
   * IllegalArgumentException} if passed a {@code fromElement} smaller than an earlier {@code
   * fromElement}. However, this method doesn't throw an exception in that situation, but instead
   * keeps the original {@code fromElement}. Similarly, this method keeps the original {@code
   * toElement}, instead of throwing an exception, if passed a {@code toElement} greater than an
   * earlier {@code toElement}.
   */
  @Override
  public ImmutableSortedSet<E> subSet(E fromElement, E toElement) {
    return subSet(fromElement, true, toElement, false);
  }

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public ImmutableSortedSet<E> subSet(
      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
    checkNotNull(fromElement);
    checkNotNull(toElement);
    checkArgument(comparator.compare(fromElement, toElement) <= 0);
    return subSetImpl(fromElement, fromInclusive, toElement, toInclusive);
  }

  /**
   * {@inheritDoc}
   *
   * <p>This method returns a serializable {@code ImmutableSortedSet}.
   *
   * <p>The {@link SortedSet#tailSet} documentation states that a subset of a subset throws an
   * {@link IllegalArgumentException} if passed a {@code fromElement} smaller than an earlier {@code
   * fromElement}. However, this method doesn't throw an exception in that situation, but instead
   * keeps the original {@code fromElement}.
   */
  @Override
  public ImmutableSortedSet<E> tailSet(E fromElement) {
    return tailSet(fromElement, true);
  }

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public ImmutableSortedSet<E> tailSet(E fromElement, boolean inclusive) {
    return tailSetImpl(checkNotNull(fromElement), inclusive);
  }

  /*
   * These methods perform most headSet, subSet, and tailSet logic, besides
   * parameter validation.
   */
  abstract ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive);

  abstract ImmutableSortedSet<E> subSetImpl(
      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive);

  abstract ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive);

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public E lower(E e) {
    return Iterators.getNext(headSet(e, false).descendingIterator(), null);
  }

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public E floor(E e) {
    return Iterators.getNext(headSet(e, true).descendingIterator(), null);
  }

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public E ceiling(E e) {
    return Iterables.getFirst(tailSet(e, true), null);
  }

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public E higher(E e) {
    return Iterables.getFirst(tailSet(e, false), null);
  }

  @Override
  public E first() {
    return iterator().next();
  }

  @Override
  public E last() {
    return descendingIterator().next();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @GwtIncompatible("NavigableSet")
  @Override
  public final E pollFirst() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @GwtIncompatible("NavigableSet")
  @Override
  public final E pollLast() {
    throw new UnsupportedOperationException();
  }

  @GwtIncompatible("NavigableSet")
  transient ImmutableSortedSet<E> descendingSet;

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public ImmutableSortedSet<E> descendingSet() {
    // racy single-check idiom
    ImmutableSortedSet<E> result = descendingSet;
    if (result == null) {
      result = descendingSet = createDescendingSet();
      result.descendingSet = this;
    }
    return result;
  }

  @GwtIncompatible("NavigableSet")
  ImmutableSortedSet<E> createDescendingSet() {
    return new DescendingImmutableSortedSet<E>(this);
  }

  /** @since 12.0 */
  @GwtIncompatible("NavigableSet")
  @Override
  public abstract UnmodifiableIterator<E> descendingIterator();

  /** Returns the position of an element within the set, or -1 if not present. */
  abstract int indexOf(@Nullable Object target);

  /*
   * This class is used to serialize all ImmutableSortedSet instances,
   * regardless of implementation type. It captures their "logical contents"
   * only. This is necessary to ensure that the existence of a particular
   * implementation type is an implementation detail.
   */
  private static class SerializedForm<E> implements Serializable {
    final Comparator<? super E> comparator;
    final Object[] elements;

    public SerializedForm(Comparator<? super E> comparator, Object[] elements) {
      this.comparator = comparator;
      this.elements = elements;
    }

    @SuppressWarnings("unchecked")
    Object readResolve() {
      return new Builder<E>(comparator).add((E[]) elements).build();
    }

    private static final long serialVersionUID = 0;
  }

  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  @Override
  Object writeReplace() {
    return new SerializedForm<E>(comparator, toArray());
  }
}