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
017 package com.google.common.collect;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkNotNull;
021
022 import com.google.common.annotations.GwtCompatible;
023 import com.google.common.annotations.GwtIncompatible;
024
025 import java.io.InvalidObjectException;
026 import java.io.ObjectInputStream;
027 import java.io.Serializable;
028 import java.util.ArrayList;
029 import java.util.Arrays;
030 import java.util.Collection;
031 import java.util.Collections;
032 import java.util.Comparator;
033 import java.util.Iterator;
034 import java.util.List;
035 import java.util.NavigableSet;
036 import java.util.SortedSet;
037
038 import javax.annotation.Nullable;
039
040 /**
041 * An immutable {@code SortedSet} that stores its elements in a sorted array.
042 * Some instances are ordered by an explicit comparator, while others follow the
043 * natural sort ordering of their elements. Either way, null elements are not
044 * supported.
045 *
046 * <p>Unlike {@link Collections#unmodifiableSortedSet}, which is a <i>view</i>
047 * of a separate collection that can still change, an instance of {@code
048 * ImmutableSortedSet} contains its own private data and will <i>never</i>
049 * change. This class is convenient for {@code public static final} sets
050 * ("constant sets") and also lets you easily make a "defensive copy" of a set
051 * provided to your class by a caller.
052 *
053 * <p>The sets returned by the {@link #headSet}, {@link #tailSet}, and
054 * {@link #subSet} methods share the same array as the original set, preventing
055 * that array from being garbage collected. If this is a concern, the data may
056 * be copied into a correctly-sized array by calling {@link #copyOfSorted}.
057 *
058 * <p><b>Note on element equivalence:</b> The {@link #contains(Object)},
059 * {@link #containsAll(Collection)}, and {@link #equals(Object)}
060 * implementations must check whether a provided object is equivalent to an
061 * element in the collection. Unlike most collections, an
062 * {@code ImmutableSortedSet} doesn't use {@link Object#equals} to determine if
063 * two elements are equivalent. Instead, with an explicit comparator, the
064 * following relation determines whether elements {@code x} and {@code y} are
065 * equivalent: <pre> {@code
066 *
067 * {(x, y) | comparator.compare(x, y) == 0}}</pre>
068 *
069 * With natural ordering of elements, the following relation determines whether
070 * two elements are equivalent: <pre> {@code
071 *
072 * {(x, y) | x.compareTo(y) == 0}}</pre>
073 *
074 * <b>Warning:</b> Like most sets, an {@code ImmutableSortedSet} will not
075 * function correctly if an element is modified after being placed in the set.
076 * For this reason, and to avoid general confusion, it is strongly recommended
077 * to place only immutable objects into this collection.
078 *
079 * <p><b>Note:</b> Although this class is not final, it cannot be subclassed as
080 * it has no public or protected constructors. Thus, instances of this type are
081 * guaranteed to be immutable.
082 *
083 * <p>See the Guava User Guide article on <a href=
084 * "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained">
085 * immutable collections</a>.
086 *
087 * @see ImmutableSet
088 * @author Jared Levy
089 * @author Louis Wasserman
090 * @since 2.0 (imported from Google Collections Library; implements {@code NavigableSet} since 12.0)
091 */
092 // TODO(benyu): benchmark and optimize all creation paths, which are a mess now
093 @GwtCompatible(serializable = true, emulated = true)
094 @SuppressWarnings("serial") // we're overriding default serialization
095 public abstract class ImmutableSortedSet<E> extends ImmutableSortedSetFauxverideShim<E>
096 implements NavigableSet<E>, SortedIterable<E> {
097
098 private static final Comparator<Comparable> NATURAL_ORDER =
099 Ordering.natural();
100
101 private static final ImmutableSortedSet<Comparable> NATURAL_EMPTY_SET =
102 new EmptyImmutableSortedSet<Comparable>(NATURAL_ORDER);
103
104 @SuppressWarnings("unchecked")
105 private static <E> ImmutableSortedSet<E> emptySet() {
106 return (ImmutableSortedSet<E>) NATURAL_EMPTY_SET;
107 }
108
109 static <E> ImmutableSortedSet<E> emptySet(
110 Comparator<? super E> comparator) {
111 if (NATURAL_ORDER.equals(comparator)) {
112 return emptySet();
113 } else {
114 return new EmptyImmutableSortedSet<E>(comparator);
115 }
116 }
117
118 /**
119 * Returns the empty immutable sorted set.
120 */
121 public static <E> ImmutableSortedSet<E> of() {
122 return emptySet();
123 }
124
125 /**
126 * Returns an immutable sorted set containing a single element.
127 */
128 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
129 E element) {
130 return new RegularImmutableSortedSet<E>(
131 ImmutableList.of(element), Ordering.natural());
132 }
133
134 /**
135 * Returns an immutable sorted set containing the given elements sorted by
136 * their natural ordering. When multiple elements are equivalent according to
137 * {@link Comparable#compareTo}, only the first one specified is included.
138 *
139 * @throws NullPointerException if any element is null
140 */
141 @SuppressWarnings("unchecked")
142 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
143 E e1, E e2) {
144 return copyOf(Ordering.natural(), Arrays.asList(e1, e2));
145 }
146
147 /**
148 * Returns an immutable sorted set containing the given elements sorted by
149 * their natural ordering. When multiple elements are equivalent according to
150 * {@link Comparable#compareTo}, only the first one specified is included.
151 *
152 * @throws NullPointerException if any element is null
153 */
154 @SuppressWarnings("unchecked")
155 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
156 E e1, E e2, E e3) {
157 return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3));
158 }
159
160 /**
161 * Returns an immutable sorted set containing the given elements sorted by
162 * their natural ordering. When multiple elements are equivalent according to
163 * {@link Comparable#compareTo}, only the first one specified is included.
164 *
165 * @throws NullPointerException if any element is null
166 */
167 @SuppressWarnings("unchecked")
168 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
169 E e1, E e2, E e3, E e4) {
170 return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3, e4));
171 }
172
173 /**
174 * Returns an immutable sorted set containing the given elements sorted by
175 * their natural ordering. When multiple elements are equivalent according to
176 * {@link Comparable#compareTo}, only the first one specified is included.
177 *
178 * @throws NullPointerException if any element is null
179 */
180 @SuppressWarnings("unchecked")
181 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
182 E e1, E e2, E e3, E e4, E e5) {
183 return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3, e4, e5));
184 }
185
186 /**
187 * Returns an immutable sorted set containing the given elements sorted by
188 * their natural ordering. When multiple elements are equivalent according to
189 * {@link Comparable#compareTo}, only the first one specified is included.
190 *
191 * @throws NullPointerException if any element is null
192 * @since 3.0 (source-compatible since 2.0)
193 */
194 @SuppressWarnings("unchecked")
195 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> of(
196 E e1, E e2, E e3, E e4, E e5, E e6, E... remaining) {
197 int size = remaining.length + 6;
198 List<E> all = new ArrayList<E>(size);
199 Collections.addAll(all, e1, e2, e3, e4, e5, e6);
200 Collections.addAll(all, remaining);
201 return copyOf(Ordering.natural(), all);
202 }
203
204 // TODO(kevinb): Consider factory methods that reject duplicates
205
206 /**
207 * Returns an immutable sorted set containing the given elements sorted by
208 * their natural ordering. When multiple elements are equivalent according to
209 * {@link Comparable#compareTo}, only the first one specified is included.
210 *
211 * @throws NullPointerException if any of {@code elements} is null
212 * @since 3.0
213 */
214 public static <E extends Comparable<? super E>> ImmutableSortedSet<E> copyOf(
215 E[] elements) {
216 return copyOf(Ordering.natural(), Arrays.asList(elements));
217 }
218
219 /**
220 * Returns an immutable sorted set containing the given elements sorted by
221 * their natural ordering. When multiple elements are equivalent according to
222 * {@code compareTo()}, only the first one specified is included. To create a
223 * copy of a {@code SortedSet} that preserves the comparator, call {@link
224 * #copyOfSorted} instead. This method iterates over {@code elements} at most
225 * once.
226
227 *
228 * <p>Note that if {@code s} is a {@code Set<String>}, then {@code
229 * ImmutableSortedSet.copyOf(s)} returns an {@code ImmutableSortedSet<String>}
230 * containing each of the strings in {@code s}, while {@code
231 * ImmutableSortedSet.of(s)} returns an {@code
232 * ImmutableSortedSet<Set<String>>} containing one element (the given set
233 * itself).
234 *
235 * <p>Despite the method name, this method attempts to avoid actually copying
236 * the data when it is safe to do so. The exact circumstances under which a
237 * copy will or will not be performed are undocumented and subject to change.
238 *
239 * <p>This method is not type-safe, as it may be called on elements that are
240 * not mutually comparable.
241 *
242 * @throws ClassCastException if the elements are not mutually comparable
243 * @throws NullPointerException if any of {@code elements} is null
244 */
245 public static <E> ImmutableSortedSet<E> copyOf(
246 Iterable<? 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
256 * their natural ordering. When multiple elements are equivalent according to
257 * {@code compareTo()}, only the first one specified is included. To create a
258 * copy of a {@code SortedSet} that preserves the comparator, call
259 * {@link #copyOfSorted} instead. This method iterates over {@code elements}
260 * at most once.
261 *
262 * <p>Note that if {@code s} is a {@code Set<String>}, then
263 * {@code ImmutableSortedSet.copyOf(s)} returns an
264 * {@code ImmutableSortedSet<String>} containing each of the strings in
265 * {@code s}, while {@code ImmutableSortedSet.of(s)} returns an
266 * {@code ImmutableSortedSet<Set<String>>} containing one element (the given
267 * set itself).
268 *
269 * <p><b>Note:</b> Despite what the method name suggests, if {@code elements}
270 * is an {@code ImmutableSortedSet}, it may be returned instead of a copy.
271 *
272 * <p>This method is not type-safe, as it may be called on elements that are
273 * not mutually comparable.
274 *
275 * <p>This method is safe to use even when {@code elements} is a synchronized
276 * or concurrent collection that is currently being modified by another
277 * thread.
278 *
279 * @throws ClassCastException if the elements are not mutually comparable
280 * @throws NullPointerException if any of {@code elements} is null
281 * @since 7.0 (source-compatible since 2.0)
282 */
283 public static <E> ImmutableSortedSet<E> copyOf(
284 Collection<? extends E> elements) {
285 // Hack around E not being a subtype of Comparable.
286 // Unsafe, see ImmutableSortedSetFauxverideShim.
287 @SuppressWarnings("unchecked")
288 Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable>natural();
289 return copyOf(naturalOrder, elements);
290 }
291
292 /**
293 * Returns an immutable sorted set containing the given elements sorted by
294 * their natural ordering. When multiple elements are equivalent according to
295 * {@code compareTo()}, only the first one specified is included.
296 *
297 * <p>This method is not type-safe, as it may be called on elements that are
298 * not mutually comparable.
299 *
300 * @throws ClassCastException if the elements are not mutually comparable
301 * @throws NullPointerException if any of {@code elements} is null
302 */
303 public static <E> ImmutableSortedSet<E> copyOf(
304 Iterator<? extends E> elements) {
305 // Hack around E not being a subtype of Comparable.
306 // Unsafe, see ImmutableSortedSetFauxverideShim.
307 @SuppressWarnings("unchecked")
308 Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable>natural();
309 return copyOf(naturalOrder, elements);
310 }
311
312 /**
313 * Returns an immutable sorted set containing the given elements sorted by
314 * the given {@code Comparator}. When multiple elements are equivalent
315 * according to {@code compareTo()}, only the first one specified is
316 * included.
317 *
318 * @throws NullPointerException if {@code comparator} or any of
319 * {@code elements} is null
320 */
321 public static <E> ImmutableSortedSet<E> copyOf(
322 Comparator<? super E> comparator, Iterator<? extends E> elements) {
323 return copyOf(comparator, Lists.newArrayList(elements));
324 }
325
326 /**
327 * Returns an immutable sorted set containing the given elements sorted by
328 * the given {@code Comparator}. When multiple elements are equivalent
329 * according to {@code compare()}, only the first one specified is
330 * included. This method iterates over {@code elements} at most once.
331 *
332 * <p>Despite the method name, this method attempts to avoid actually copying
333 * the data when it is safe to do so. The exact circumstances under which a
334 * copy will or will not be performed are undocumented and subject to change.
335 *
336 * @throws NullPointerException if {@code comparator} or any of {@code
337 * elements} is null
338 */
339 public static <E> ImmutableSortedSet<E> copyOf(
340 Comparator<? super E> comparator, Iterable<? extends E> elements) {
341 checkNotNull(comparator);
342 boolean hasSameComparator =
343 SortedIterables.hasSameComparator(comparator, elements);
344
345 if (hasSameComparator && (elements instanceof ImmutableSortedSet)) {
346 @SuppressWarnings("unchecked")
347 ImmutableSortedSet<E> original = (ImmutableSortedSet<E>) elements;
348 if (!original.isPartialView()) {
349 return original;
350 }
351 }
352 @SuppressWarnings("unchecked") // elements only contains E's; it's safe.
353 E[] array = (E[]) Iterables.toArray(elements);
354 return construct(comparator, array.length, array);
355 }
356
357 /**
358 * Returns an immutable sorted set containing the given elements sorted by
359 * the given {@code Comparator}. When multiple elements are equivalent
360 * according to {@code compareTo()}, only the first one specified is
361 * included.
362 *
363 * <p>Despite the method name, this method attempts to avoid actually copying
364 * the data when it is safe to do so. The exact circumstances under which a
365 * copy will or will not be performed are undocumented and subject to change.
366 *
367 * <p>This method is safe to use even when {@code elements} is a synchronized
368 * or concurrent collection that is currently being modified by another
369 * thread.
370 *
371 * @throws NullPointerException if {@code comparator} or any of
372 * {@code elements} is null
373 * @since 7.0 (source-compatible since 2.0)
374 */
375 public static <E> ImmutableSortedSet<E> copyOf(
376 Comparator<? super E> comparator, Collection<? extends E> elements) {
377 return copyOf(comparator, (Iterable<? extends E>) elements);
378 }
379
380 /**
381 * Returns an immutable sorted set containing the elements of a sorted set,
382 * sorted by the same {@code Comparator}. That behavior differs from {@link
383 * #copyOf(Iterable)}, which always uses the natural ordering of the
384 * elements.
385 *
386 * <p>Despite the method name, this method attempts to avoid actually copying
387 * the data when it is safe to do so. The exact circumstances under which a
388 * copy will or will not be performed are undocumented and subject to change.
389 *
390 * <p>This method is safe to use even when {@code sortedSet} is a synchronized
391 * or concurrent collection that is currently being modified by another
392 * thread.
393 *
394 * @throws NullPointerException if {@code sortedSet} or any of its elements
395 * is null
396 */
397 @SuppressWarnings("unchecked")
398 public static <E> ImmutableSortedSet<E> copyOfSorted(SortedSet<E> sortedSet) {
399 Comparator<? super E> comparator = sortedSet.comparator();
400 if (comparator == null) {
401 comparator = (Comparator<? super E>) NATURAL_ORDER;
402 }
403 E[] elements = (E[]) sortedSet.toArray();
404 if (elements.length == 0) {
405 return emptySet(comparator);
406 } else {
407 return new RegularImmutableSortedSet<E>(
408 ImmutableList.<E>asImmutableList(elements), comparator);
409 }
410 }
411
412 /**
413 * Sorts and eliminates duplicates from the first {@code n} positions in {@code contents}.
414 * Returns the number of unique elements. If this returns {@code k}, then the first {@code k}
415 * elements of {@code contents} will be the sorted, unique elements, and {@code
416 * contents[i] == null} for {@code k <= i < n}.
417 *
418 * @throws NullPointerException if any of the first {@code n} elements of {@code contents} is
419 * null
420 */
421 static <E> int sortAndUnique(
422 Comparator<? super E> comparator, int n, E... contents) {
423 if (n == 0) {
424 return 0;
425 }
426 for (int i = 0; i < n; i++) {
427 ObjectArrays.checkElementNotNull(contents[i], i);
428 }
429 Arrays.sort(contents, 0, n, comparator);
430 int uniques = 1;
431 for (int i = 1; i < n; i++) {
432 E cur = contents[i];
433 E prev = contents[uniques - 1];
434 if (comparator.compare(cur, prev) != 0) {
435 contents[uniques++] = cur;
436 }
437 }
438 Arrays.fill(contents, uniques, n, null);
439 return uniques;
440 }
441
442 /**
443 * Constructs an {@code ImmutableSortedSet} from the first {@code n} elements of
444 * {@code contents}. If {@code k} is the size of the returned {@code ImmutableSortedSet}, then
445 * the sorted unique elements are in the first {@code k} positions of {@code contents}, and
446 * {@code contents[i] == null} for {@code k <= i < n}.
447 *
448 * <p>If {@code k == contents.length}, then {@code contents} may no longer be safe for
449 * modification.
450 *
451 * @throws NullPointerException if any of the first {@code n} elements of {@code contents} is
452 * null
453 */
454 static <E> ImmutableSortedSet<E> construct(
455 Comparator<? super E> comparator, int n, E... contents) {
456 int uniques = sortAndUnique(comparator, n, contents);
457 if (uniques == 0) {
458 return emptySet(comparator);
459 } else if (uniques < contents.length) {
460 contents = ObjectArrays.arraysCopyOf(contents, uniques);
461 }
462 return new RegularImmutableSortedSet<E>(
463 ImmutableList.<E>asImmutableList(contents), comparator);
464 }
465
466 /**
467 * Returns a builder that creates immutable sorted sets with an explicit
468 * comparator. If the comparator has a more general type than the set being
469 * generated, such as creating a {@code SortedSet<Integer>} with a
470 * {@code Comparator<Number>}, use the {@link Builder} constructor instead.
471 *
472 * @throws NullPointerException if {@code comparator} is null
473 */
474 public static <E> Builder<E> orderedBy(Comparator<E> comparator) {
475 return new Builder<E>(comparator);
476 }
477
478 /**
479 * Returns a builder that creates immutable sorted sets whose elements are
480 * ordered by the reverse of their natural ordering.
481 *
482 * <p>Note: the type parameter {@code E} extends {@code Comparable<E>} rather
483 * than {@code Comparable<? super E>} as a workaround for javac <a
484 * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6468354">bug
485 * 6468354</a>.
486 */
487 public static <E extends Comparable<E>> Builder<E> reverseOrder() {
488 return new Builder<E>(Ordering.natural().reverse());
489 }
490
491 /**
492 * Returns a builder that creates immutable sorted sets whose elements are
493 * ordered by their natural ordering. The sorted sets use {@link
494 * Ordering#natural()} as the comparator. This method provides more
495 * type-safety than {@link #builder}, as it can be called only for classes
496 * that implement {@link Comparable}.
497 *
498 * <p>Note: the type parameter {@code E} extends {@code Comparable<E>} rather
499 * than {@code Comparable<? super E>} as a workaround for javac <a
500 * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6468354">bug
501 * 6468354</a>.
502 */
503 public static <E extends Comparable<E>> Builder<E> naturalOrder() {
504 return new Builder<E>(Ordering.natural());
505 }
506
507 /**
508 * A builder for creating immutable sorted set instances, especially {@code
509 * public static final} sets ("constant sets"), with a given comparator.
510 * Example: <pre> {@code
511 *
512 * public static final ImmutableSortedSet<Number> LUCKY_NUMBERS =
513 * new ImmutableSortedSet.Builder<Number>(ODDS_FIRST_COMPARATOR)
514 * .addAll(SINGLE_DIGIT_PRIMES)
515 * .add(42)
516 * .build();}</pre>
517 *
518 * Builder instances can be reused; it is safe to call {@link #build} multiple
519 * times to build multiple sets in series. Each set is a superset of the set
520 * created before it.
521 *
522 * @since 2.0 (imported from Google Collections Library)
523 */
524 public static final class Builder<E> extends ImmutableSet.Builder<E> {
525 private final Comparator<? super E> comparator;
526
527 /**
528 * Creates a new builder. The returned builder is equivalent to the builder
529 * generated by {@link ImmutableSortedSet#orderedBy}.
530 */
531 public Builder(Comparator<? super E> comparator) {
532 this.comparator = checkNotNull(comparator);
533 }
534
535 /**
536 * Adds {@code element} to the {@code ImmutableSortedSet}. If the
537 * {@code ImmutableSortedSet} already contains {@code element}, then
538 * {@code add} has no effect. (only the previously added element
539 * is retained).
540 *
541 * @param element the element to add
542 * @return this {@code Builder} object
543 * @throws NullPointerException if {@code element} is null
544 */
545 @Override public Builder<E> add(E element) {
546 super.add(element);
547 return this;
548 }
549
550 /**
551 * Adds each element of {@code elements} to the {@code ImmutableSortedSet},
552 * ignoring duplicate elements (only the first duplicate element is added).
553 *
554 * @param elements the elements to add
555 * @return this {@code Builder} object
556 * @throws NullPointerException if {@code elements} contains a null element
557 */
558 @Override public Builder<E> add(E... elements) {
559 super.add(elements);
560 return this;
561 }
562
563 /**
564 * Adds each element of {@code elements} to the {@code ImmutableSortedSet},
565 * ignoring duplicate elements (only the first duplicate element is added).
566 *
567 * @param elements the elements to add to the {@code ImmutableSortedSet}
568 * @return this {@code Builder} object
569 * @throws NullPointerException if {@code elements} contains a null element
570 */
571 @Override public Builder<E> addAll(Iterable<? extends E> elements) {
572 super.addAll(elements);
573 return this;
574 }
575
576 /**
577 * Adds each element of {@code elements} to the {@code ImmutableSortedSet},
578 * ignoring duplicate elements (only the first duplicate element is added).
579 *
580 * @param elements the elements to add to the {@code ImmutableSortedSet}
581 * @return this {@code Builder} object
582 * @throws NullPointerException if {@code elements} contains a null element
583 */
584 @Override public Builder<E> addAll(Iterator<? extends E> elements) {
585 super.addAll(elements);
586 return this;
587 }
588
589 /**
590 * Returns a newly-created {@code ImmutableSortedSet} based on the contents
591 * of the {@code Builder} and its comparator.
592 */
593 @Override public ImmutableSortedSet<E> build() {
594 @SuppressWarnings("unchecked") // we're careful to put only E's in here
595 E[] contentsArray = (E[]) contents;
596 ImmutableSortedSet<E> result = construct(comparator, size, contentsArray);
597 this.size = result.size(); // we eliminated duplicates in-place in contentsArray
598 return result;
599 }
600 }
601
602 int unsafeCompare(Object a, Object b) {
603 return unsafeCompare(comparator, a, b);
604 }
605
606 static int unsafeCompare(
607 Comparator<?> comparator, Object a, Object b) {
608 // Pretend the comparator can compare anything. If it turns out it can't
609 // compare a and b, we should get a CCE on the subsequent line. Only methods
610 // that are spec'd to throw CCE should call this.
611 @SuppressWarnings("unchecked")
612 Comparator<Object> unsafeComparator = (Comparator<Object>) comparator;
613 return unsafeComparator.compare(a, b);
614 }
615
616 final transient Comparator<? super E> comparator;
617
618 ImmutableSortedSet(Comparator<? super E> comparator) {
619 this.comparator = comparator;
620 }
621
622 /**
623 * Returns the comparator that orders the elements, which is
624 * {@link Ordering#natural()} when the natural ordering of the
625 * elements is used. Note that its behavior is not consistent with
626 * {@link SortedSet#comparator()}, which returns {@code null} to indicate
627 * natural ordering.
628 */
629 @Override
630 public Comparator<? super E> comparator() {
631 return comparator;
632 }
633
634 @Override // needed to unify the iterator() methods in Collection and SortedIterable
635 public abstract UnmodifiableIterator<E> iterator();
636
637 /**
638 * {@inheritDoc}
639 *
640 * <p>This method returns a serializable {@code ImmutableSortedSet}.
641 *
642 * <p>The {@link SortedSet#headSet} documentation states that a subset of a
643 * subset throws an {@link IllegalArgumentException} if passed a
644 * {@code toElement} greater than an earlier {@code toElement}. However, this
645 * method doesn't throw an exception in that situation, but instead keeps the
646 * original {@code toElement}.
647 */
648 @Override
649 public ImmutableSortedSet<E> headSet(E toElement) {
650 return headSet(toElement, false);
651 }
652
653 /**
654 * @since 12.0
655 */
656 @GwtIncompatible("NavigableSet")
657 @Override
658 public ImmutableSortedSet<E> headSet(E toElement, boolean inclusive) {
659 return headSetImpl(checkNotNull(toElement), inclusive);
660 }
661
662 /**
663 * {@inheritDoc}
664 *
665 * <p>This method returns a serializable {@code ImmutableSortedSet}.
666 *
667 * <p>The {@link SortedSet#subSet} documentation states that a subset of a
668 * subset throws an {@link IllegalArgumentException} if passed a
669 * {@code fromElement} smaller than an earlier {@code fromElement}. However,
670 * this method doesn't throw an exception in that situation, but instead keeps
671 * the original {@code fromElement}. Similarly, this method keeps the
672 * original {@code toElement}, instead of throwing an exception, if passed a
673 * {@code toElement} greater than an earlier {@code toElement}.
674 */
675 @Override
676 public ImmutableSortedSet<E> subSet(E fromElement, E toElement) {
677 return subSet(fromElement, true, toElement, false);
678 }
679
680 /**
681 * @since 12.0
682 */
683 @GwtIncompatible("NavigableSet")
684 @Override
685 public ImmutableSortedSet<E> subSet(
686 E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
687 checkNotNull(fromElement);
688 checkNotNull(toElement);
689 checkArgument(comparator.compare(fromElement, toElement) <= 0);
690 return subSetImpl(fromElement, fromInclusive, toElement, toInclusive);
691 }
692
693 /**
694 * {@inheritDoc}
695 *
696 * <p>This method returns a serializable {@code ImmutableSortedSet}.
697 *
698 * <p>The {@link SortedSet#tailSet} documentation states that a subset of a
699 * subset throws an {@link IllegalArgumentException} if passed a
700 * {@code fromElement} smaller than an earlier {@code fromElement}. However,
701 * this method doesn't throw an exception in that situation, but instead keeps
702 * the original {@code fromElement}.
703 */
704 @Override
705 public ImmutableSortedSet<E> tailSet(E fromElement) {
706 return tailSet(fromElement, true);
707 }
708
709 /**
710 * @since 12.0
711 */
712 @GwtIncompatible("NavigableSet")
713 @Override
714 public ImmutableSortedSet<E> tailSet(E fromElement, boolean inclusive) {
715 return tailSetImpl(checkNotNull(fromElement), inclusive);
716 }
717
718 /*
719 * These methods perform most headSet, subSet, and tailSet logic, besides
720 * parameter validation.
721 */
722 abstract ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive);
723
724 abstract ImmutableSortedSet<E> subSetImpl(
725 E fromElement, boolean fromInclusive, E toElement, boolean toInclusive);
726
727 abstract ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive);
728
729 /**
730 * @since 12.0
731 */
732 @GwtIncompatible("NavigableSet")
733 @Override
734 public E lower(E e) {
735 return Iterables.getFirst(headSet(e, false).descendingSet(), null);
736 }
737
738 /**
739 * @since 12.0
740 */
741 @GwtIncompatible("NavigableSet")
742 @Override
743 public E floor(E e) {
744 return Iterables.getFirst(headSet(e, true).descendingSet(), null);
745 }
746
747 /**
748 * @since 12.0
749 */
750 @GwtIncompatible("NavigableSet")
751 @Override
752 public E ceiling(E e) {
753 return Iterables.getFirst(tailSet(e, true), null);
754 }
755
756 /**
757 * @since 12.0
758 */
759 @GwtIncompatible("NavigableSet")
760 @Override
761 public E higher(E e) {
762 return Iterables.getFirst(tailSet(e, false), null);
763 }
764
765 /**
766 * @since 12.0
767 */
768 @GwtIncompatible("NavigableSet")
769 @Override
770 public final E pollFirst() {
771 throw new UnsupportedOperationException();
772 }
773
774 /**
775 * @since 12.0
776 */
777 @GwtIncompatible("NavigableSet")
778 @Override
779 public final E pollLast() {
780 throw new UnsupportedOperationException();
781 }
782
783 @GwtIncompatible("NavigableSet")
784 transient ImmutableSortedSet<E> descendingSet;
785
786 /**
787 * @since 12.0
788 */
789 @GwtIncompatible("NavigableSet")
790 @Override
791 public ImmutableSortedSet<E> descendingSet() {
792 ImmutableSortedSet<E> result = descendingSet;
793 if (result == null) {
794 result = descendingSet = createDescendingSet();
795 result.descendingSet = this;
796 }
797 return result;
798 }
799
800 @GwtIncompatible("NavigableSet")
801 abstract ImmutableSortedSet<E> createDescendingSet();
802
803 /**
804 * @since 12.0
805 */
806 @GwtIncompatible("NavigableSet")
807 @Override
808 public UnmodifiableIterator<E> descendingIterator() {
809 return descendingSet().iterator();
810 }
811
812 /**
813 * Returns the position of an element within the set, or -1 if not present.
814 */
815 abstract int indexOf(@Nullable Object target);
816
817 /*
818 * This class is used to serialize all ImmutableSortedSet instances,
819 * regardless of implementation type. It captures their "logical contents"
820 * only. This is necessary to ensure that the existence of a particular
821 * implementation type is an implementation detail.
822 */
823 private static class SerializedForm<E> implements Serializable {
824 final Comparator<? super E> comparator;
825 final Object[] elements;
826
827 public SerializedForm(Comparator<? super E> comparator, Object[] elements) {
828 this.comparator = comparator;
829 this.elements = elements;
830 }
831
832 @SuppressWarnings("unchecked")
833 Object readResolve() {
834 return new Builder<E>(comparator).add((E[]) elements).build();
835 }
836
837 private static final long serialVersionUID = 0;
838 }
839
840 private void readObject(ObjectInputStream stream)
841 throws InvalidObjectException {
842 throw new InvalidObjectException("Use SerializedForm");
843 }
844
845 @Override Object writeReplace() {
846 return new SerializedForm<E>(comparator, toArray());
847 }
848 }
849