001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkNotNull;
021import static com.google.common.collect.ObjectArrays.checkElementsNotNull;
022
023import com.google.common.annotations.GwtCompatible;
024import com.google.common.annotations.GwtIncompatible;
025import com.google.common.annotations.J2ktIncompatible;
026import com.google.errorprone.annotations.CanIgnoreReturnValue;
027import com.google.errorprone.annotations.DoNotCall;
028import com.google.errorprone.annotations.concurrent.LazyInit;
029import java.io.InvalidObjectException;
030import java.io.ObjectInputStream;
031import java.io.Serializable;
032import java.util.Arrays;
033import java.util.Collection;
034import java.util.Collections;
035import java.util.Comparator;
036import java.util.Iterator;
037import java.util.NavigableSet;
038import java.util.SortedSet;
039import java.util.Spliterator;
040import java.util.Spliterators;
041import java.util.function.Consumer;
042import java.util.stream.Collector;
043import javax.annotation.CheckForNull;
044import org.checkerframework.checker.nullness.qual.Nullable;
045
046/**
047 * A {@link NavigableSet} whose contents will never change, with many other important properties
048 * detailed at {@link ImmutableCollection}.
049 *
050 * <p><b>Warning:</b> as with any sorted collection, you are strongly advised not to use a {@link
051 * Comparator} or {@link Comparable} type whose comparison behavior is <i>inconsistent with
052 * equals</i>. That is, {@code a.compareTo(b)} or {@code comparator.compare(a, b)} should equal zero
053 * <i>if and only if</i> {@code a.equals(b)}. If this advice is not followed, the resulting
054 * collection will not correctly obey its specification.
055 *
056 * <p>See the Guava User Guide article on <a href=
057 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">immutable collections</a>.
058 *
059 * @author Jared Levy
060 * @author Louis Wasserman
061 * @since 2.0 (implements {@code NavigableSet} since 12.0)
062 */
063// TODO(benyu): benchmark and optimize all creation paths, which are a mess now
064@GwtCompatible(serializable = true, emulated = true)
065@SuppressWarnings("serial") // we're overriding default serialization
066@ElementTypesAreNonnullByDefault
067public abstract class ImmutableSortedSet<E> extends ImmutableSet.CachingAsList<E>
068    implements NavigableSet<E>, SortedIterable<E> {
069  static final int SPLITERATOR_CHARACTERISTICS =
070      ImmutableSet.SPLITERATOR_CHARACTERISTICS | Spliterator.SORTED;
071
072  /**
073   * Returns a {@code Collector} that accumulates the input elements into a new {@code
074   * ImmutableSortedSet}, ordered by the specified comparator.
075   *
076   * <p>If the elements contain duplicates (according to the comparator), only the first duplicate
077   * in encounter order will appear in the result.
078   *
079   * @since 21.0
080   */
081  public static <E> Collector<E, ?, ImmutableSortedSet<E>> toImmutableSortedSet(
082      Comparator<? super E> comparator) {
083    return CollectCollectors.toImmutableSortedSet(comparator);
084  }
085
086  static <E> RegularImmutableSortedSet<E> emptySet(Comparator<? super E> comparator) {
087    if (Ordering.natural().equals(comparator)) {
088      @SuppressWarnings("unchecked") // The natural-ordered empty set supports all types.
089      RegularImmutableSortedSet<E> result =
090          (RegularImmutableSortedSet<E>) RegularImmutableSortedSet.NATURAL_EMPTY_SET;
091      return result;
092    } else {
093      return new RegularImmutableSortedSet<>(ImmutableList.of(), comparator);
094    }
095  }
096
097  /**
098   * Returns the empty immutable sorted set.
099   *
100   * <p><b>Performance note:</b> the instance returned is a singleton.
101   */
102  @SuppressWarnings("unchecked") // The natural-ordered empty set supports all types.
103  public static <E> ImmutableSortedSet<E> of() {
104    return (ImmutableSortedSet<E>) RegularImmutableSortedSet.NATURAL_EMPTY_SET;
105  }
106
107  /** Returns an immutable sorted set containing a single element. */
108  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E element) {
109    return new RegularImmutableSortedSet<>(ImmutableList.of(element), Ordering.natural());
110  }
111
112  /**
113   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
114   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
115   * one specified is included.
116   *
117   * @throws NullPointerException if any element is null
118   */
119  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E e1, E e2) {
120    return construct(Ordering.natural(), 2, e1, e2);
121  }
122
123  /**
124   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
125   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
126   * one specified is included.
127   *
128   * @throws NullPointerException if any element is null
129   */
130  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E e1, E e2, E e3) {
131    return construct(Ordering.natural(), 3, e1, e2, e3);
132  }
133
134  /**
135   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
136   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
137   * one specified is included.
138   *
139   * @throws NullPointerException if any element is null
140   */
141  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(E e1, E e2, E e3, E e4) {
142    return construct(Ordering.natural(), 4, e1, e2, e3, e4);
143  }
144
145  /**
146   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
147   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
148   * one specified is included.
149   *
150   * @throws NullPointerException if any element is null
151   */
152  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
153      E e1, E e2, E e3, E e4, E e5) {
154    return construct(Ordering.natural(), 5, e1, e2, e3, e4, e5);
155  }
156
157  /**
158   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
159   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
160   * one specified is included.
161   *
162   * @throws NullPointerException if any element is null
163   * @since 3.0 (source-compatible since 2.0)
164   */
165  @SuppressWarnings("unchecked")
166  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
167      E e1, E e2, E e3, E e4, E e5, E e6, E... remaining) {
168    Comparable<?>[] contents = new Comparable<?>[6 + remaining.length];
169    contents[0] = e1;
170    contents[1] = e2;
171    contents[2] = e3;
172    contents[3] = e4;
173    contents[4] = e5;
174    contents[5] = e6;
175    System.arraycopy(remaining, 0, contents, 6, remaining.length);
176    return construct(Ordering.natural(), contents.length, (E[]) contents);
177  }
178
179  // TODO(kevinb): Consider factory methods that reject duplicates
180
181  /**
182   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
183   * When multiple elements are equivalent according to {@link Comparable#compareTo}, only the first
184   * one specified is included.
185   *
186   * @throws NullPointerException if any of {@code elements} is null
187   * @since 3.0
188   */
189  public static <E extends Comparable<? super E>> ImmutableSortedSet<E> copyOf(E[] elements) {
190    return construct(Ordering.natural(), elements.length, elements.clone());
191  }
192
193  /**
194   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
195   * When multiple elements are equivalent according to {@code compareTo()}, only the first one
196   * specified is included. To create a copy of a {@code SortedSet} that preserves the comparator,
197   * call {@link #copyOfSorted} instead. This method iterates over {@code elements} at most once.
198   *
199   * <p>Note that if {@code s} is a {@code Set<String>}, then {@code ImmutableSortedSet.copyOf(s)}
200   * returns an {@code ImmutableSortedSet<String>} containing each of the strings in {@code s},
201   * while {@code ImmutableSortedSet.of(s)} returns an {@code ImmutableSortedSet<Set<String>>}
202   * containing one element (the given set itself).
203   *
204   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
205   * safe to do so. The exact circumstances under which a copy will or will not be performed are
206   * undocumented and subject to change.
207   *
208   * <p>This method is not type-safe, as it may be called on elements that are not mutually
209   * comparable.
210   *
211   * @throws ClassCastException if the elements are not mutually comparable
212   * @throws NullPointerException if any of {@code elements} is null
213   */
214  public static <E> ImmutableSortedSet<E> copyOf(Iterable<? extends E> elements) {
215    // Hack around E not being a subtype of Comparable.
216    // Unsafe, see ImmutableSortedSetFauxverideShim.
217    @SuppressWarnings("unchecked")
218    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable<?>>natural();
219    return copyOf(naturalOrder, elements);
220  }
221
222  /**
223   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
224   * When multiple elements are equivalent according to {@code compareTo()}, only the first one
225   * specified is included. To create a copy of a {@code SortedSet} that preserves the comparator,
226   * call {@link #copyOfSorted} instead. This method iterates over {@code elements} at most once.
227   *
228   * <p>Note that if {@code s} is a {@code Set<String>}, then {@code ImmutableSortedSet.copyOf(s)}
229   * returns an {@code ImmutableSortedSet<String>} containing each of the strings in {@code s},
230   * while {@code ImmutableSortedSet.of(s)} returns an {@code ImmutableSortedSet<Set<String>>}
231   * containing one element (the given set itself).
232   *
233   * <p><b>Note:</b> Despite what the method name suggests, if {@code elements} is an {@code
234   * ImmutableSortedSet}, it may be returned instead of a copy.
235   *
236   * <p>This method is not type-safe, as it may be called on elements that are not mutually
237   * comparable.
238   *
239   * <p>This method is safe to use even when {@code elements} is a synchronized or concurrent
240   * collection that is currently being modified by another thread.
241   *
242   * @throws ClassCastException if the elements are not mutually comparable
243   * @throws NullPointerException if any of {@code elements} is null
244   * @since 7.0 (source-compatible since 2.0)
245   */
246  public static <E> ImmutableSortedSet<E> copyOf(Collection<? extends E> elements) {
247    // Hack around E not being a subtype of Comparable.
248    // Unsafe, see ImmutableSortedSetFauxverideShim.
249    @SuppressWarnings("unchecked")
250    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable<?>>natural();
251    return copyOf(naturalOrder, elements);
252  }
253
254  /**
255   * Returns an immutable sorted set containing the given elements sorted by their natural ordering.
256   * When multiple elements are equivalent according to {@code compareTo()}, only the first one
257   * specified is included.
258   *
259   * <p>This method is not type-safe, as it may be called on elements that are not mutually
260   * comparable.
261   *
262   * @throws ClassCastException if the elements are not mutually comparable
263   * @throws NullPointerException if any of {@code elements} is null
264   */
265  public static <E> ImmutableSortedSet<E> copyOf(Iterator<? extends E> elements) {
266    // Hack around E not being a subtype of Comparable.
267    // Unsafe, see ImmutableSortedSetFauxverideShim.
268    @SuppressWarnings("unchecked")
269    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable<?>>natural();
270    return copyOf(naturalOrder, elements);
271  }
272
273  /**
274   * Returns an immutable sorted set containing the given elements sorted by the given {@code
275   * Comparator}. When multiple elements are equivalent according to {@code compareTo()}, only the
276   * first one specified is included.
277   *
278   * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
279   */
280  public static <E> ImmutableSortedSet<E> copyOf(
281      Comparator<? super E> comparator, Iterator<? extends E> elements) {
282    return new Builder<E>(comparator).addAll(elements).build();
283  }
284
285  /**
286   * Returns an immutable sorted set containing the given elements sorted by the given {@code
287   * Comparator}. When multiple elements are equivalent according to {@code compare()}, only the
288   * first one specified is included. This method iterates over {@code elements} at most once.
289   *
290   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
291   * safe to do so. The exact circumstances under which a copy will or will not be performed are
292   * undocumented and subject to change.
293   *
294   * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
295   */
296  public static <E> ImmutableSortedSet<E> copyOf(
297      Comparator<? super E> comparator, Iterable<? extends E> elements) {
298    checkNotNull(comparator);
299    boolean hasSameComparator = SortedIterables.hasSameComparator(comparator, elements);
300
301    if (hasSameComparator && (elements instanceof ImmutableSortedSet)) {
302      @SuppressWarnings("unchecked")
303      ImmutableSortedSet<E> original = (ImmutableSortedSet<E>) elements;
304      if (!original.isPartialView()) {
305        return original;
306      }
307    }
308    @SuppressWarnings("unchecked") // elements only contains E's; it's safe.
309    E[] array = (E[]) Iterables.toArray(elements);
310    return construct(comparator, array.length, array);
311  }
312
313  /**
314   * Returns an immutable sorted set containing the given elements sorted by the given {@code
315   * Comparator}. When multiple elements are equivalent according to {@code compareTo()}, only the
316   * first one specified is included.
317   *
318   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
319   * safe to do so. The exact circumstances under which a copy will or will not be performed are
320   * undocumented and subject to change.
321   *
322   * <p>This method is safe to use even when {@code elements} is a synchronized or concurrent
323   * collection that is currently being modified by another thread.
324   *
325   * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
326   * @since 7.0 (source-compatible since 2.0)
327   */
328  public static <E> ImmutableSortedSet<E> copyOf(
329      Comparator<? super E> comparator, Collection<? extends E> elements) {
330    return copyOf(comparator, (Iterable<? extends E>) elements);
331  }
332
333  /**
334   * Returns an immutable sorted set containing the elements of a sorted set, sorted by the same
335   * {@code Comparator}. That behavior differs from {@link #copyOf(Iterable)}, which always uses the
336   * natural ordering of the elements.
337   *
338   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
339   * safe to do so. The exact circumstances under which a copy will or will not be performed are
340   * undocumented and subject to change.
341   *
342   * <p>This method is safe to use even when {@code sortedSet} is a synchronized or concurrent
343   * collection that is currently being modified by another thread.
344   *
345   * @throws NullPointerException if {@code sortedSet} or any of its elements is null
346   */
347  public static <E> ImmutableSortedSet<E> copyOfSorted(SortedSet<E> sortedSet) {
348    Comparator<? super E> comparator = SortedIterables.comparator(sortedSet);
349    ImmutableList<E> list = ImmutableList.copyOf(sortedSet);
350    if (list.isEmpty()) {
351      return emptySet(comparator);
352    } else {
353      return new RegularImmutableSortedSet<>(list, comparator);
354    }
355  }
356
357  /**
358   * Constructs an {@code ImmutableSortedSet} from the first {@code n} elements of {@code contents}.
359   * If {@code k} is the size of the returned {@code ImmutableSortedSet}, then the sorted unique
360   * elements are in the first {@code k} positions of {@code contents}, and {@code contents[i] ==
361   * null} for {@code k <= i < n}.
362   *
363   * <p>This method takes ownership of {@code contents}; do not modify {@code contents} after this
364   * returns.
365   *
366   * @throws NullPointerException if any of the first {@code n} elements of {@code contents} is null
367   */
368  static <E> ImmutableSortedSet<E> construct(
369      Comparator<? super E> comparator, int n, E... contents) {
370    if (n == 0) {
371      return emptySet(comparator);
372    }
373    checkElementsNotNull(contents, n);
374    Arrays.sort(contents, 0, n, comparator);
375    int uniques = 1;
376    for (int i = 1; i < n; i++) {
377      E cur = contents[i];
378      E prev = contents[uniques - 1];
379      if (comparator.compare(cur, prev) != 0) {
380        contents[uniques++] = cur;
381      }
382    }
383    Arrays.fill(contents, uniques, n, null);
384    return new RegularImmutableSortedSet<>(
385        ImmutableList.<E>asImmutableList(contents, uniques), comparator);
386  }
387
388  /**
389   * Returns a builder that creates immutable sorted sets with an explicit comparator. If the
390   * comparator has a more general type than the set being generated, such as creating a {@code
391   * SortedSet<Integer>} with a {@code Comparator<Number>}, use the {@link Builder} constructor
392   * instead.
393   *
394   * @throws NullPointerException if {@code comparator} is null
395   */
396  public static <E> Builder<E> orderedBy(Comparator<E> comparator) {
397    return new Builder<>(comparator);
398  }
399
400  /**
401   * Returns a builder that creates immutable sorted sets whose elements are ordered by the reverse
402   * of their natural ordering.
403   */
404  public static <E extends Comparable<?>> Builder<E> reverseOrder() {
405    return new Builder<>(Collections.reverseOrder());
406  }
407
408  /**
409   * Returns a builder that creates immutable sorted sets whose elements are ordered by their
410   * natural ordering. The sorted sets use {@link Ordering#natural()} as the comparator. This method
411   * provides more type-safety than {@link #builder}, as it can be called only for classes that
412   * implement {@link Comparable}.
413   */
414  public static <E extends Comparable<?>> Builder<E> naturalOrder() {
415    return new Builder<>(Ordering.natural());
416  }
417
418  /**
419   * A builder for creating immutable sorted set instances, especially {@code public static final}
420   * sets ("constant sets"), with a given comparator. Example:
421   *
422   * <pre>{@code
423   * public static final ImmutableSortedSet<Number> LUCKY_NUMBERS =
424   *     new ImmutableSortedSet.Builder<Number>(ODDS_FIRST_COMPARATOR)
425   *         .addAll(SINGLE_DIGIT_PRIMES)
426   *         .add(42)
427   *         .build();
428   * }</pre>
429   *
430   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
431   * multiple sets in series. Each set is a superset of the set created before it.
432   *
433   * @since 2.0
434   */
435  public static final class Builder<E> extends ImmutableSet.Builder<E> {
436    private final Comparator<? super E> comparator;
437    private E[] elements;
438    private int n;
439
440    /**
441     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
442     * ImmutableSortedSet#orderedBy}.
443     */
444    /*
445     * TODO(cpovirk): use Object[] instead of E[] in the mainline? (The backport is different and
446     * doesn't need this suppression, but we keep it to minimize diffs.) Generally be more clear
447     * about when we have an Object[] vs. a Comparable[] or other array type in internalArray? If we
448     * used Object[], we might be able to optimize toArray() to use clone() sometimes. (See
449     * cl/592273615 and cl/592273683.)
450     */
451    @SuppressWarnings("unchecked")
452    public Builder(Comparator<? super E> comparator) {
453      super(true); // don't construct guts of hash-based set builder
454      this.comparator = checkNotNull(comparator);
455      this.elements = (E[]) new Object[ImmutableCollection.Builder.DEFAULT_INITIAL_CAPACITY];
456      this.n = 0;
457    }
458
459    @Override
460    void copy() {
461      elements = Arrays.copyOf(elements, elements.length);
462    }
463
464    private void sortAndDedup() {
465      if (n == 0) {
466        return;
467      }
468      Arrays.sort(elements, 0, n, comparator);
469      int unique = 1;
470      for (int i = 1; i < n; i++) {
471        int cmp = comparator.compare(elements[unique - 1], elements[i]);
472        if (cmp < 0) {
473          elements[unique++] = elements[i];
474        } else if (cmp > 0) {
475          throw new AssertionError(
476              "Comparator " + comparator + " compare method violates its contract");
477        }
478      }
479      Arrays.fill(elements, unique, n, null);
480      n = unique;
481    }
482
483    /**
484     * Adds {@code element} to the {@code ImmutableSortedSet}. If the {@code ImmutableSortedSet}
485     * already contains {@code element}, then {@code add} has no effect. (only the previously added
486     * element is retained).
487     *
488     * @param element the element to add
489     * @return this {@code Builder} object
490     * @throws NullPointerException if {@code element} is null
491     */
492    @CanIgnoreReturnValue
493    @Override
494    public Builder<E> add(E element) {
495      checkNotNull(element);
496      copyIfNecessary();
497      if (n == elements.length) {
498        sortAndDedup();
499        /*
500         * Sorting operations can only be allowed to occur once every O(n) operations to keep
501         * amortized O(n log n) performance.  Therefore, ensure there are at least O(n) *unused*
502         * spaces in the builder array.
503         */
504        int newLength = ImmutableCollection.Builder.expandedCapacity(n, n + 1);
505        if (newLength > elements.length) {
506          elements = Arrays.copyOf(elements, newLength);
507        }
508      }
509      elements[n++] = element;
510      return this;
511    }
512
513    /**
514     * Adds each element of {@code elements} to the {@code ImmutableSortedSet}, ignoring duplicate
515     * elements (only the first duplicate element is added).
516     *
517     * @param elements the elements to add
518     * @return this {@code Builder} object
519     * @throws NullPointerException if {@code elements} contains a null element
520     */
521    @CanIgnoreReturnValue
522    @Override
523    public Builder<E> add(E... elements) {
524      checkElementsNotNull(elements);
525      for (E e : elements) {
526        add(e);
527      }
528      return this;
529    }
530
531    /**
532     * Adds each element of {@code elements} to the {@code ImmutableSortedSet}, ignoring duplicate
533     * elements (only the first duplicate element is added).
534     *
535     * @param elements the elements to add to the {@code ImmutableSortedSet}
536     * @return this {@code Builder} object
537     * @throws NullPointerException if {@code elements} contains a null element
538     */
539    @CanIgnoreReturnValue
540    @Override
541    public Builder<E> addAll(Iterable<? extends E> elements) {
542      super.addAll(elements);
543      return this;
544    }
545
546    /**
547     * Adds each element of {@code elements} to the {@code ImmutableSortedSet}, ignoring duplicate
548     * elements (only the first duplicate element is added).
549     *
550     * @param elements the elements to add to the {@code ImmutableSortedSet}
551     * @return this {@code Builder} object
552     * @throws NullPointerException if {@code elements} contains a null element
553     */
554    @CanIgnoreReturnValue
555    @Override
556    public Builder<E> addAll(Iterator<? extends E> elements) {
557      super.addAll(elements);
558      return this;
559    }
560
561    @CanIgnoreReturnValue
562    @Override
563    Builder<E> combine(ImmutableSet.Builder<E> builder) {
564      copyIfNecessary();
565      Builder<E> other = (Builder<E>) builder;
566      for (int i = 0; i < other.n; i++) {
567        add(other.elements[i]);
568      }
569      return this;
570    }
571
572    /**
573     * Returns a newly-created {@code ImmutableSortedSet} based on the contents of the {@code
574     * Builder} and its comparator.
575     */
576    @Override
577    public ImmutableSortedSet<E> build() {
578      sortAndDedup();
579      if (n == 0) {
580        return emptySet(comparator);
581      } else {
582        forceCopy = true;
583        return new RegularImmutableSortedSet<>(
584            ImmutableList.asImmutableList(elements, n), comparator);
585      }
586    }
587  }
588
589  int unsafeCompare(Object a, @CheckForNull Object b) {
590    return unsafeCompare(comparator, a, b);
591  }
592
593  static int unsafeCompare(Comparator<?> comparator, Object a, @CheckForNull Object b) {
594    // Pretend the comparator can compare anything. If it turns out it can't
595    // compare a and b, we should get a CCE or NPE on the subsequent line. Only methods
596    // that are spec'd to throw CCE and NPE should call this.
597    @SuppressWarnings({"unchecked", "nullness"})
598    Comparator<@Nullable Object> unsafeComparator = (Comparator<@Nullable Object>) comparator;
599    return unsafeComparator.compare(a, b);
600  }
601
602  final transient Comparator<? super E> comparator;
603
604  ImmutableSortedSet(Comparator<? super E> comparator) {
605    this.comparator = comparator;
606  }
607
608  /**
609   * Returns the comparator that orders the elements, which is {@link Ordering#natural()} when the
610   * natural ordering of the elements is used. Note that its behavior is not consistent with {@link
611   * SortedSet#comparator()}, which returns {@code null} to indicate natural ordering.
612   */
613  @Override
614  public Comparator<? super E> comparator() {
615    return comparator;
616  }
617
618  @Override // needed to unify the iterator() methods in Collection and SortedIterable
619  public abstract UnmodifiableIterator<E> iterator();
620
621  /**
622   * {@inheritDoc}
623   *
624   * <p>This method returns a serializable {@code ImmutableSortedSet}.
625   *
626   * <p>The {@link SortedSet#headSet} documentation states that a subset of a subset throws an
627   * {@link IllegalArgumentException} if passed a {@code toElement} greater than an earlier {@code
628   * toElement}. However, this method doesn't throw an exception in that situation, but instead
629   * keeps the original {@code toElement}.
630   */
631  @Override
632  public ImmutableSortedSet<E> headSet(E toElement) {
633    return headSet(toElement, false);
634  }
635
636  /** @since 12.0 */
637  @Override
638  public ImmutableSortedSet<E> headSet(E toElement, boolean inclusive) {
639    return headSetImpl(checkNotNull(toElement), inclusive);
640  }
641
642  /**
643   * {@inheritDoc}
644   *
645   * <p>This method returns a serializable {@code ImmutableSortedSet}.
646   *
647   * <p>The {@link SortedSet#subSet} documentation states that a subset of a subset throws an {@link
648   * IllegalArgumentException} if passed a {@code fromElement} smaller than an earlier {@code
649   * fromElement}. However, this method doesn't throw an exception in that situation, but instead
650   * keeps the original {@code fromElement}. Similarly, this method keeps the original {@code
651   * toElement}, instead of throwing an exception, if passed a {@code toElement} greater than an
652   * earlier {@code toElement}.
653   */
654  @Override
655  public ImmutableSortedSet<E> subSet(E fromElement, E toElement) {
656    return subSet(fromElement, true, toElement, false);
657  }
658
659  /** @since 12.0 */
660  @GwtIncompatible // NavigableSet
661  @Override
662  public ImmutableSortedSet<E> subSet(
663      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
664    checkNotNull(fromElement);
665    checkNotNull(toElement);
666    checkArgument(comparator.compare(fromElement, toElement) <= 0);
667    return subSetImpl(fromElement, fromInclusive, toElement, toInclusive);
668  }
669
670  /**
671   * {@inheritDoc}
672   *
673   * <p>This method returns a serializable {@code ImmutableSortedSet}.
674   *
675   * <p>The {@link SortedSet#tailSet} documentation states that a subset of a subset throws an
676   * {@link IllegalArgumentException} if passed a {@code fromElement} smaller than an earlier {@code
677   * fromElement}. However, this method doesn't throw an exception in that situation, but instead
678   * keeps the original {@code fromElement}.
679   */
680  @Override
681  public ImmutableSortedSet<E> tailSet(E fromElement) {
682    return tailSet(fromElement, true);
683  }
684
685  /** @since 12.0 */
686  @Override
687  public ImmutableSortedSet<E> tailSet(E fromElement, boolean inclusive) {
688    return tailSetImpl(checkNotNull(fromElement), inclusive);
689  }
690
691  /*
692   * These methods perform most headSet, subSet, and tailSet logic, besides
693   * parameter validation.
694   */
695  abstract ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive);
696
697  abstract ImmutableSortedSet<E> subSetImpl(
698      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive);
699
700  abstract ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive);
701
702  /** @since 12.0 */
703  @GwtIncompatible // NavigableSet
704  @Override
705  @CheckForNull
706  public E lower(E e) {
707    return Iterators.<@Nullable E>getNext(headSet(e, false).descendingIterator(), null);
708  }
709
710  /** @since 12.0 */
711  @Override
712  @CheckForNull
713  public E floor(E e) {
714    return Iterators.<@Nullable E>getNext(headSet(e, true).descendingIterator(), null);
715  }
716
717  /** @since 12.0 */
718  @Override
719  @CheckForNull
720  public E ceiling(E e) {
721    return Iterables.<@Nullable E>getFirst(tailSet(e, true), null);
722  }
723
724  /** @since 12.0 */
725  @GwtIncompatible // NavigableSet
726  @Override
727  @CheckForNull
728  public E higher(E e) {
729    return Iterables.<@Nullable E>getFirst(tailSet(e, false), null);
730  }
731
732  @Override
733  public E first() {
734    return iterator().next();
735  }
736
737  @Override
738  public E last() {
739    return descendingIterator().next();
740  }
741
742  /**
743   * Guaranteed to throw an exception and leave the set unmodified.
744   *
745   * @since 12.0
746   * @throws UnsupportedOperationException always
747   * @deprecated Unsupported operation.
748   */
749  @CanIgnoreReturnValue
750  @Deprecated
751  @GwtIncompatible // NavigableSet
752  @Override
753  @DoNotCall("Always throws UnsupportedOperationException")
754  @CheckForNull
755  public final E pollFirst() {
756    throw new UnsupportedOperationException();
757  }
758
759  /**
760   * Guaranteed to throw an exception and leave the set unmodified.
761   *
762   * @since 12.0
763   * @throws UnsupportedOperationException always
764   * @deprecated Unsupported operation.
765   */
766  @CanIgnoreReturnValue
767  @Deprecated
768  @GwtIncompatible // NavigableSet
769  @Override
770  @DoNotCall("Always throws UnsupportedOperationException")
771  @CheckForNull
772  public final E pollLast() {
773    throw new UnsupportedOperationException();
774  }
775
776  @GwtIncompatible // NavigableSet
777  @LazyInit
778  @CheckForNull
779  transient ImmutableSortedSet<E> descendingSet;
780
781  /** @since 12.0 */
782  @GwtIncompatible // NavigableSet
783  @Override
784  public ImmutableSortedSet<E> descendingSet() {
785    // racy single-check idiom
786    ImmutableSortedSet<E> result = descendingSet;
787    if (result == null) {
788      result = descendingSet = createDescendingSet();
789      result.descendingSet = this;
790    }
791    return result;
792  }
793
794  // Most classes should implement this as new DescendingImmutableSortedSet<E>(this),
795  // but we push down that implementation because ProGuard can't eliminate it even when it's always
796  // overridden.
797  @GwtIncompatible // NavigableSet
798  abstract ImmutableSortedSet<E> createDescendingSet();
799
800  @Override
801  public Spliterator<E> spliterator() {
802    return new Spliterators.AbstractSpliterator<E>(
803        size(), SPLITERATOR_CHARACTERISTICS | Spliterator.SIZED) {
804      final UnmodifiableIterator<E> iterator = iterator();
805
806      @Override
807      public boolean tryAdvance(Consumer<? super E> action) {
808        if (iterator.hasNext()) {
809          action.accept(iterator.next());
810          return true;
811        } else {
812          return false;
813        }
814      }
815
816      @Override
817      public Comparator<? super E> getComparator() {
818        return comparator;
819      }
820    };
821  }
822
823  /** @since 12.0 */
824  @GwtIncompatible // NavigableSet
825  @Override
826  public abstract UnmodifiableIterator<E> descendingIterator();
827
828  /** Returns the position of an element within the set, or -1 if not present. */
829  abstract int indexOf(@CheckForNull Object target);
830
831  /*
832   * This class is used to serialize all ImmutableSortedSet instances,
833   * regardless of implementation type. It captures their "logical contents"
834   * only. This is necessary to ensure that the existence of a particular
835   * implementation type is an implementation detail.
836   */
837  @J2ktIncompatible // serialization
838  private static class SerializedForm<E> implements Serializable {
839    final Comparator<? super E> comparator;
840    final Object[] elements;
841
842    public SerializedForm(Comparator<? super E> comparator, Object[] elements) {
843      this.comparator = comparator;
844      this.elements = elements;
845    }
846
847    @SuppressWarnings("unchecked")
848    Object readResolve() {
849      return new Builder<E>(comparator).add((E[]) elements).build();
850    }
851
852    private static final long serialVersionUID = 0;
853  }
854
855  @J2ktIncompatible // serialization
856  private void readObject(ObjectInputStream unused) throws InvalidObjectException {
857    throw new InvalidObjectException("Use SerializedForm");
858  }
859
860  @Override
861  @J2ktIncompatible // serialization
862  Object writeReplace() {
863    return new SerializedForm<E>(comparator, toArray());
864  }
865
866  /**
867   * Not supported. Use {@link #toImmutableSortedSet} instead. This method exists only to hide
868   * {@link ImmutableSet#toImmutableSet} from consumers of {@code ImmutableSortedSet}.
869   *
870   * @throws UnsupportedOperationException always
871   * @deprecated Use {@link ImmutableSortedSet#toImmutableSortedSet}.
872   * @since 21.0
873   */
874  @DoNotCall("Use toImmutableSortedSet")
875  @Deprecated
876  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
877    throw new UnsupportedOperationException();
878  }
879
880  /**
881   * Not supported. Use {@link #naturalOrder}, which offers better type-safety, instead. This method
882   * exists only to hide {@link ImmutableSet#builder} from consumers of {@code ImmutableSortedSet}.
883   *
884   * @throws UnsupportedOperationException always
885   * @deprecated Use {@link ImmutableSortedSet#naturalOrder}, which offers better type-safety.
886   */
887  @DoNotCall("Use naturalOrder")
888  @Deprecated
889  public static <E> ImmutableSortedSet.Builder<E> builder() {
890    throw new UnsupportedOperationException();
891  }
892
893  /**
894   * Not supported. This method exists only to hide {@link ImmutableSet#builderWithExpectedSize}
895   * from consumers of {@code ImmutableSortedSet}.
896   *
897   * @throws UnsupportedOperationException always
898   * @deprecated Not supported by ImmutableSortedSet.
899   */
900  @DoNotCall("Use naturalOrder (which does not accept an expected size)")
901  @Deprecated
902  public static <E> ImmutableSortedSet.Builder<E> builderWithExpectedSize(int expectedSize) {
903    throw new UnsupportedOperationException();
904  }
905
906  /**
907   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
908   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
909   * dummy version.
910   *
911   * @throws UnsupportedOperationException always
912   * @deprecated <b>Pass a parameter of type {@code Comparable} to use {@link
913   *     ImmutableSortedSet#of(Comparable)}.</b>
914   */
915  @DoNotCall("Pass a parameter of type Comparable")
916  @Deprecated
917  public static <E> ImmutableSortedSet<E> of(E element) {
918    throw new UnsupportedOperationException();
919  }
920
921  /**
922   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
923   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
924   * dummy version.
925   *
926   * @throws UnsupportedOperationException always
927   * @deprecated <b>Pass the parameters of type {@code Comparable} to use {@link
928   *     ImmutableSortedSet#of(Comparable, Comparable)}.</b>
929   */
930  @DoNotCall("Pass parameters of type Comparable")
931  @Deprecated
932  public static <E> ImmutableSortedSet<E> of(E e1, E e2) {
933    throw new UnsupportedOperationException();
934  }
935
936  /**
937   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
938   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
939   * dummy version.
940   *
941   * @throws UnsupportedOperationException always
942   * @deprecated <b>Pass the parameters of type {@code Comparable} to use {@link
943   *     ImmutableSortedSet#of(Comparable, Comparable, Comparable)}.</b>
944   */
945  @DoNotCall("Pass parameters of type Comparable")
946  @Deprecated
947  public static <E> ImmutableSortedSet<E> of(E e1, E e2, E e3) {
948    throw new UnsupportedOperationException();
949  }
950
951  /**
952   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
953   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
954   * dummy version.
955   *
956   * @throws UnsupportedOperationException always
957   * @deprecated <b>Pass the parameters of type {@code Comparable} to use {@link
958   *     ImmutableSortedSet#of(Comparable, Comparable, Comparable, Comparable)}. </b>
959   */
960  @DoNotCall("Pass parameters of type Comparable")
961  @Deprecated
962  public static <E> ImmutableSortedSet<E> of(E e1, E e2, E e3, E e4) {
963    throw new UnsupportedOperationException();
964  }
965
966  /**
967   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
968   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
969   * dummy version.
970   *
971   * @throws UnsupportedOperationException always
972   * @deprecated <b>Pass the parameters of type {@code Comparable} to use {@link
973   *     ImmutableSortedSet#of( Comparable, Comparable, Comparable, Comparable, Comparable)}. </b>
974   */
975  @DoNotCall("Pass parameters of type Comparable")
976  @Deprecated
977  public static <E> ImmutableSortedSet<E> of(E e1, E e2, E e3, E e4, E e5) {
978    throw new UnsupportedOperationException();
979  }
980
981  /**
982   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
983   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
984   * dummy version.
985   *
986   * @throws UnsupportedOperationException always
987   * @deprecated <b>Pass the parameters of type {@code Comparable} to use {@link
988   *     ImmutableSortedSet#of(Comparable, Comparable, Comparable, Comparable, Comparable,
989   *     Comparable, Comparable...)}. </b>
990   */
991  @DoNotCall("Pass parameters of type Comparable")
992  @Deprecated
993  public static <E> ImmutableSortedSet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E... remaining) {
994    throw new UnsupportedOperationException();
995  }
996
997  /**
998   * Not supported. <b>You are attempting to create a set that may contain non-{@code Comparable}
999   * elements.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
1000   * dummy version.
1001   *
1002   * @throws UnsupportedOperationException always
1003   * @deprecated <b>Pass parameters of type {@code Comparable} to use {@link
1004   *     ImmutableSortedSet#copyOf(Comparable[])}.</b>
1005   */
1006  @DoNotCall("Pass parameters of type Comparable")
1007  @Deprecated
1008  // The usage of "Z" here works around bugs in Javadoc (JDK-8318093) and JDiff.
1009  public static <Z> ImmutableSortedSet<Z> copyOf(Z[] elements) {
1010    throw new UnsupportedOperationException();
1011  }
1012
1013  private static final long serialVersionUID = 0xcafebabe;
1014}