001 /*
002 * Copyright (C) 2011 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the
010 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
011 * express or implied. See the License for the specific language governing permissions and
012 * limitations under the License.
013 */
014
015 package com.google.common.collect;
016
017 import static com.google.common.base.Preconditions.checkArgument;
018 import static com.google.common.base.Preconditions.checkNotNull;
019
020 import com.google.common.annotations.Beta;
021 import com.google.common.annotations.GwtIncompatible;
022
023 import java.io.Serializable;
024 import java.util.Arrays;
025 import java.util.Collection;
026 import java.util.Collections;
027 import java.util.Comparator;
028 import java.util.Iterator;
029 import java.util.List;
030
031 /**
032 * An immutable {@code SortedMultiset} that stores its elements in a sorted array. Some instances
033 * are ordered by an explicit comparator, while others follow the natural sort ordering of their
034 * elements. Either way, null elements are not supported.
035 *
036 * <p>Unlike {@link Multisets#unmodifiableSortedMultiset}, which is a <i>view</i> of a separate
037 * collection that can still change, an instance of {@code ImmutableSortedMultiset} contains its
038 * own private data and will <i>never</i> change. This class is convenient for {@code public static
039 * final} multisets ("constant multisets") and also lets you easily make a "defensive copy" of a
040 * set provided to your class by a caller.
041 *
042 * <p>The multisets returned by the {@link #headMultiset}, {@link #tailMultiset}, and
043 * {@link #subMultiset} methods share the same array as the original multiset, preventing that
044 * array from being garbage collected. If this is a concern, the data may be copied into a
045 * correctly-sized array by calling {@link #copyOfSorted}.
046 *
047 * <p><b>Note on element equivalence:</b> The {@link #contains(Object)},
048 * {@link #containsAll(Collection)}, and {@link #equals(Object)} implementations must check whether
049 * a provided object is equivalent to an element in the collection. Unlike most collections, an
050 * {@code ImmutableSortedMultiset} doesn't use {@link Object#equals} to determine if two elements
051 * are equivalent. Instead, with an explicit comparator, the following relation determines whether
052 * elements {@code x} and {@code y} are equivalent:
053 *
054 * <pre> {@code
055 *
056 * {(x, y) | comparator.compare(x, y) == 0}}</pre>
057 *
058 * With natural ordering of elements, the following relation determines whether two elements are
059 * equivalent:
060 *
061 * <pre> {@code
062 *
063 * {(x, y) | x.compareTo(y) == 0}}</pre>
064 *
065 * <b>Warning:</b> Like most multisets, an {@code ImmutableSortedMultiset} will not function
066 * correctly if an element is modified after being placed in the multiset. For this reason, and to
067 * avoid general confusion, it is strongly recommended to place only immutable objects into this
068 * collection.
069 *
070 * <p><b>Note:</b> Although this class is not final, it cannot be subclassed as it has no public or
071 * protected constructors. Thus, instances of this type are guaranteed to be immutable.
072 *
073 * <p>See the Guava User Guide article on <a href=
074 * "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained">
075 * immutable collections</a>.
076 *
077 * @author Louis Wasserman
078 * @since 12.0
079 */
080 @Beta
081 @GwtIncompatible("hasn't been tested yet")
082 public abstract class ImmutableSortedMultiset<E> extends ImmutableSortedMultisetFauxverideShim<E>
083 implements SortedMultiset<E> {
084 // TODO(user): GWT compatibility
085
086 private static final Comparator<Comparable> NATURAL_ORDER = Ordering.natural();
087
088 private static final ImmutableSortedMultiset<Comparable> NATURAL_EMPTY_MULTISET =
089 new EmptyImmutableSortedMultiset<Comparable>(NATURAL_ORDER);
090
091 /**
092 * Returns the empty immutable sorted multiset.
093 */
094 @SuppressWarnings("unchecked")
095 public static <E> ImmutableSortedMultiset<E> of() {
096 return (ImmutableSortedMultiset) NATURAL_EMPTY_MULTISET;
097 }
098
099 /**
100 * Returns an immutable sorted multiset containing a single element.
101 */
102 public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(E element) {
103 RegularImmutableSortedSet<E> elementSet =
104 (RegularImmutableSortedSet<E>) ImmutableSortedSet.of(element);
105 int[] counts = {1};
106 long[] cumulativeCounts = {0, 1};
107 return new RegularImmutableSortedMultiset<E>(elementSet, counts, cumulativeCounts, 0, 1);
108 }
109
110 /**
111 * Returns an immutable sorted multiset containing the given elements sorted by their natural
112 * ordering.
113 *
114 * @throws NullPointerException if any element is null
115 */
116 @SuppressWarnings("unchecked")
117 public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(E e1, E e2) {
118 return copyOf(Ordering.natural(), Arrays.asList(e1, e2));
119 }
120
121 /**
122 * Returns an immutable sorted multiset containing the given elements sorted by their natural
123 * ordering.
124 *
125 * @throws NullPointerException if any element is null
126 */
127 @SuppressWarnings("unchecked")
128 public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(E e1, E e2, E e3) {
129 return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3));
130 }
131
132 /**
133 * Returns an immutable sorted multiset containing the given elements sorted by their natural
134 * ordering.
135 *
136 * @throws NullPointerException if any element is null
137 */
138 @SuppressWarnings("unchecked")
139 public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(
140 E e1, E e2, E e3, E e4) {
141 return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3, e4));
142 }
143
144 /**
145 * Returns an immutable sorted multiset containing the given elements sorted by their natural
146 * ordering.
147 *
148 * @throws NullPointerException if any element is null
149 */
150 @SuppressWarnings("unchecked")
151 public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(
152 E e1, E e2, E e3, E e4, E e5) {
153 return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3, e4, e5));
154 }
155
156 /**
157 * Returns an immutable sorted multiset containing the given elements sorted by their natural
158 * ordering.
159 *
160 * @throws NullPointerException if any element is null
161 */
162 @SuppressWarnings("unchecked")
163 public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> of(
164 E e1, E e2, E e3, E e4, E e5, E e6, E... remaining) {
165 int size = remaining.length + 6;
166 List<E> all = Lists.newArrayListWithCapacity(size);
167 Collections.addAll(all, e1, e2, e3, e4, e5, e6);
168 Collections.addAll(all, remaining);
169 return copyOf(Ordering.natural(), all);
170 }
171
172 /**
173 * Returns an immutable sorted multiset containing the given elements sorted by their natural
174 * ordering.
175 *
176 * @throws NullPointerException if any of {@code elements} is null
177 */
178 public static <E extends Comparable<? super E>> ImmutableSortedMultiset<E> copyOf(E[] elements) {
179 return copyOf(Ordering.natural(), Arrays.asList(elements));
180 }
181
182 /**
183 * Returns an immutable sorted multiset containing the given elements sorted by their natural
184 * ordering. To create a copy of a {@code SortedMultiset} that preserves the
185 * comparator, call {@link #copyOfSorted} instead. This method iterates over {@code elements} at
186 * most once.
187 *
188 * <p>Note that if {@code s} is a {@code multiset<String>}, then {@code
189 * ImmutableSortedMultiset.copyOf(s)} returns an {@code ImmutableSortedMultiset<String>}
190 * containing each of the strings in {@code s}, while {@code ImmutableSortedMultiset.of(s)}
191 * returns an {@code ImmutableSortedMultiset<multiset<String>>} containing one element (the given
192 * multiset itself).
193 *
194 * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
195 * safe to do so. The exact circumstances under which a copy will or will not be performed are
196 * undocumented and subject to change.
197 *
198 * <p>This method is not type-safe, as it may be called on elements that are not mutually
199 * comparable.
200 *
201 * @throws ClassCastException if the elements are not mutually comparable
202 * @throws NullPointerException if any of {@code elements} is null
203 */
204 public static <E> ImmutableSortedMultiset<E> copyOf(Iterable<? extends E> elements) {
205 // Hack around E not being a subtype of Comparable.
206 // Unsafe, see ImmutableSortedMultisetFauxverideShim.
207 @SuppressWarnings("unchecked")
208 Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable>natural();
209 return copyOf(naturalOrder, elements);
210 }
211
212 /**
213 * Returns an immutable sorted multiset containing the given elements sorted by their natural
214 * ordering.
215 *
216 * <p>This method is not type-safe, as it may be called on elements that are not mutually
217 * comparable.
218 *
219 * @throws ClassCastException if the elements are not mutually comparable
220 * @throws NullPointerException if any of {@code elements} is null
221 */
222 public static <E> ImmutableSortedMultiset<E> copyOf(Iterator<? extends E> elements) {
223 // Hack around E not being a subtype of Comparable.
224 // Unsafe, see ImmutableSortedMultisetFauxverideShim.
225 @SuppressWarnings("unchecked")
226 Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable>natural();
227 return copyOf(naturalOrder, elements);
228 }
229
230 /**
231 * Returns an immutable sorted multiset containing the given elements sorted by the given {@code
232 * Comparator}.
233 *
234 * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
235 */
236 public static <E> ImmutableSortedMultiset<E> copyOf(
237 Comparator<? super E> comparator, Iterator<? extends E> elements) {
238 checkNotNull(comparator);
239 return new Builder<E>(comparator).addAll(elements).build();
240 }
241
242 /**
243 * Returns an immutable sorted multiset containing the given elements sorted by the given {@code
244 * Comparator}. This method iterates over {@code elements} at most once.
245 *
246 * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
247 * safe to do so. The exact circumstances under which a copy will or will not be performed are
248 * undocumented and subject to change.
249 *
250 * @throws NullPointerException if {@code comparator} or any of {@code elements} is null
251 */
252 public static <E> ImmutableSortedMultiset<E> copyOf(
253 Comparator<? super E> comparator, Iterable<? extends E> elements) {
254 if (elements instanceof ImmutableSortedMultiset) {
255 @SuppressWarnings("unchecked") // immutable collections are always safe for covariant casts
256 ImmutableSortedMultiset<E> multiset = (ImmutableSortedMultiset<E>) elements;
257 if (comparator.equals(multiset.comparator())) {
258 if (multiset.isPartialView()) {
259 return copyOfSortedEntries(comparator, multiset.entrySet().asList());
260 } else {
261 return multiset;
262 }
263 }
264 }
265 elements = Lists.newArrayList(elements); // defensive copy
266 TreeMultiset<E> sortedCopy = TreeMultiset.create(checkNotNull(comparator));
267 Iterables.addAll(sortedCopy, elements);
268 return copyOfSortedEntries(comparator, sortedCopy.entrySet());
269 }
270
271 /**
272 * Returns an immutable sorted multiset containing the elements of a sorted multiset, sorted by
273 * the same {@code Comparator}. That behavior differs from {@link #copyOf(Iterable)}, which
274 * always uses the natural ordering of the elements.
275 *
276 * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
277 * safe to do so. The exact circumstances under which a copy will or will not be performed are
278 * undocumented and subject to change.
279 *
280 * <p>This method is safe to use even when {@code sortedMultiset} is a synchronized or concurrent
281 * collection that is currently being modified by another thread.
282 *
283 * @throws NullPointerException if {@code sortedMultiset} or any of its elements is null
284 */
285 public static <E> ImmutableSortedMultiset<E> copyOfSorted(SortedMultiset<E> sortedMultiset) {
286 return copyOfSortedEntries(sortedMultiset.comparator(),
287 Lists.newArrayList(sortedMultiset.entrySet()));
288 }
289
290 private static <E> ImmutableSortedMultiset<E> copyOfSortedEntries(
291 Comparator<? super E> comparator, Collection<Entry<E>> entries) {
292 if (entries.isEmpty()) {
293 return emptyMultiset(comparator);
294 }
295 ImmutableList.Builder<E> elementsBuilder = new ImmutableList.Builder<E>(entries.size());
296 int[] counts = new int[entries.size()];
297 long[] cumulativeCounts = new long[entries.size() + 1];
298 int i = 0;
299 for (Entry<E> entry : entries) {
300 elementsBuilder.add(entry.getElement());
301 counts[i] = entry.getCount();
302 cumulativeCounts[i + 1] = cumulativeCounts[i] + counts[i];
303 i++;
304 }
305 return new RegularImmutableSortedMultiset<E>(
306 new RegularImmutableSortedSet<E>(elementsBuilder.build(), comparator),
307 counts, cumulativeCounts, 0, entries.size());
308 }
309
310 @SuppressWarnings("unchecked")
311 static <E> ImmutableSortedMultiset<E> emptyMultiset(Comparator<? super E> comparator) {
312 if (NATURAL_ORDER.equals(comparator)) {
313 return (ImmutableSortedMultiset) NATURAL_EMPTY_MULTISET;
314 }
315 return new EmptyImmutableSortedMultiset<E>(comparator);
316 }
317
318 ImmutableSortedMultiset() {}
319
320
321 public final Comparator<? super E> comparator() {
322 return elementSet().comparator();
323 }
324
325
326 public abstract ImmutableSortedSet<E> elementSet();
327
328 transient ImmutableSortedMultiset<E> descendingMultiset;
329
330 public ImmutableSortedMultiset<E> descendingMultiset() {
331 ImmutableSortedMultiset<E> result = descendingMultiset;
332 if (result == null) {
333 return descendingMultiset = new DescendingImmutableSortedMultiset<E>(this);
334 }
335 return result;
336 }
337
338 /**
339 * {@inheritDoc}
340 *
341 * <p>This implementation is guaranteed to throw an {@link UnsupportedOperationException}.
342 *
343 * @throws UnsupportedOperationException always
344 */
345 public final Entry<E> pollFirstEntry() {
346 throw new UnsupportedOperationException();
347 }
348
349 /**
350 * {@inheritDoc}
351 *
352 * <p>This implementation is guaranteed to throw an {@link UnsupportedOperationException}.
353 *
354 * @throws UnsupportedOperationException always
355 */
356
357 public final Entry<E> pollLastEntry() {
358 throw new UnsupportedOperationException();
359 }
360
361 public abstract ImmutableSortedMultiset<E> headMultiset(E upperBound, BoundType boundType);
362
363 public ImmutableSortedMultiset<E> subMultiset(
364 E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType) {
365 checkArgument(comparator().compare(lowerBound, upperBound) <= 0,
366 "Expected lowerBound <= upperBound but %s > %s", lowerBound, upperBound);
367 return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
368 }
369
370 public abstract ImmutableSortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);
371
372 /**
373 * Returns a builder that creates immutable sorted multisets with an explicit comparator. If the
374 * comparator has a more general type than the set being generated, such as creating a {@code
375 * SortedMultiset<Integer>} with a {@code Comparator<Number>}, use the {@link Builder}
376 * constructor instead.
377 *
378 * @throws NullPointerException if {@code comparator} is null
379 */
380 public static <E> Builder<E> orderedBy(Comparator<E> comparator) {
381 return new Builder<E>(comparator);
382 }
383
384 /**
385 * Returns a builder that creates immutable sorted multisets whose elements are ordered by the
386 * reverse of their natural ordering.
387 *
388 * <p>Note: the type parameter {@code E} extends {@code Comparable<E>} rather than {@code
389 * Comparable<? super E>} as a workaround for javac <a
390 * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6468354">bug 6468354</a>.
391 */
392 public static <E extends Comparable<E>> Builder<E> reverseOrder() {
393 return new Builder<E>(Ordering.natural().reverse());
394 }
395
396 /**
397 * Returns a builder that creates immutable sorted multisets whose elements are ordered by their
398 * natural ordering. The sorted multisets use {@link Ordering#natural()} as the comparator. This
399 * method provides more type-safety than {@link #builder}, as it can be called only for classes
400 * that implement {@link Comparable}.
401 *
402 * <p>Note: the type parameter {@code E} extends {@code Comparable<E>} rather than {@code
403 * Comparable<? super E>} as a workaround for javac <a
404 * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6468354">bug 6468354</a>.
405 */
406 public static <E extends Comparable<E>> Builder<E> naturalOrder() {
407 return new Builder<E>(Ordering.natural());
408 }
409
410 /**
411 * A builder for creating immutable multiset instances, especially {@code public static final}
412 * multisets ("constant multisets"). Example:
413 *
414 * <pre> {@code
415 *
416 * public static final ImmutableSortedMultiset<Bean> BEANS =
417 * new ImmutableSortedMultiset.Builder<Bean>()
418 * .addCopies(Bean.COCOA, 4)
419 * .addCopies(Bean.GARDEN, 6)
420 * .addCopies(Bean.RED, 8)
421 * .addCopies(Bean.BLACK_EYED, 10)
422 * .build();}</pre>
423 *
424 * Builder instances can be reused; it is safe to call {@link #build} multiple times to build
425 * multiple multisets in series.
426 *
427 * @since 12.0
428 */
429 public static class Builder<E> extends ImmutableMultiset.Builder<E> {
430 private final Comparator<? super E> comparator;
431
432 /**
433 * Creates a new builder. The returned builder is equivalent to the builder generated by
434 * {@link ImmutableSortedMultiset#orderedBy(Comparator)}.
435 */
436 public Builder(Comparator<? super E> comparator) {
437 super(TreeMultiset.<E>create(comparator));
438 this.comparator = checkNotNull(comparator);
439 }
440
441 /**
442 * Adds {@code element} to the {@code ImmutableSortedMultiset}.
443 *
444 * @param element the element to add
445 * @return this {@code Builder} object
446 * @throws NullPointerException if {@code element} is null
447 */
448
449 @Override
450 public Builder<E> add(E element) {
451 super.add(element);
452 return this;
453 }
454
455 /**
456 * Adds a number of occurrences of an element to this {@code ImmutableSortedMultiset}.
457 *
458 * @param element the element to add
459 * @param occurrences the number of occurrences of the element to add. May be zero, in which
460 * case no change will be made.
461 * @return this {@code Builder} object
462 * @throws NullPointerException if {@code element} is null
463 * @throws IllegalArgumentException if {@code occurrences} is negative, or if this operation
464 * would result in more than {@link Integer#MAX_VALUE} occurrences of the element
465 */
466
467 @Override
468 public Builder<E> addCopies(E element, int occurrences) {
469 super.addCopies(element, occurrences);
470 return this;
471 }
472
473 /**
474 * Adds or removes the necessary occurrences of an element such that the element attains the
475 * desired count.
476 *
477 * @param element the element to add or remove occurrences of
478 * @param count the desired count of the element in this multiset
479 * @return this {@code Builder} object
480 * @throws NullPointerException if {@code element} is null
481 * @throws IllegalArgumentException if {@code count} is negative
482 */
483
484 @Override
485 public Builder<E> setCount(E element, int count) {
486 super.setCount(element, count);
487 return this;
488 }
489
490 /**
491 * Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
492 *
493 * @param elements the elements to add
494 * @return this {@code Builder} object
495 * @throws NullPointerException if {@code elements} is null or contains a null element
496 */
497
498 @Override
499 public Builder<E> add(E... elements) {
500 super.add(elements);
501 return this;
502 }
503
504 /**
505 * Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
506 *
507 * @param elements the {@code Iterable} to add to the {@code ImmutableSortedMultiset}
508 * @return this {@code Builder} object
509 * @throws NullPointerException if {@code elements} is null or contains a null element
510 */
511
512 @Override
513 public Builder<E> addAll(Iterable<? extends E> elements) {
514 super.addAll(elements);
515 return this;
516 }
517
518 /**
519 * Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
520 *
521 * @param elements the elements to add to the {@code ImmutableSortedMultiset}
522 * @return this {@code Builder} object
523 * @throws NullPointerException if {@code elements} is null or contains a null element
524 */
525
526 @Override
527 public Builder<E> addAll(Iterator<? extends E> elements) {
528 super.addAll(elements);
529 return this;
530 }
531
532 /**
533 * Returns a newly-created {@code ImmutableSortedMultiset} based on the contents of the {@code
534 * Builder}.
535 */
536
537 @Override
538 public ImmutableSortedMultiset<E> build() {
539 return copyOfSorted((SortedMultiset<E>) contents);
540 }
541 }
542
543 private static final class SerializedForm implements Serializable {
544 Comparator comparator;
545 Object[] elements;
546 int[] counts;
547
548 SerializedForm(SortedMultiset<?> multiset) {
549 this.comparator = multiset.comparator();
550 int n = multiset.entrySet().size();
551 elements = new Object[n];
552 counts = new int[n];
553 int i = 0;
554 for (Entry<?> entry : multiset.entrySet()) {
555 elements[i] = entry.getElement();
556 counts[i] = entry.getCount();
557 i++;
558 }
559 }
560
561 @SuppressWarnings("unchecked")
562 Object readResolve() {
563 int n = elements.length;
564 Builder<Object> builder = orderedBy(comparator);
565 for (int i = 0; i < n; i++) {
566 builder.addCopies(elements[i], counts[i]);
567 }
568 return builder.build();
569 }
570 }
571
572
573 @Override
574 Object writeReplace() {
575 return new SerializedForm(this);
576 }
577 }