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001 /*
002 * Copyright (C) 2007 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 import static com.google.common.base.Preconditions.checkState;
022 import static com.google.common.collect.BstSide.LEFT;
023 import static com.google.common.collect.BstSide.RIGHT;
024
025 import java.io.IOException;
026 import java.io.ObjectInputStream;
027 import java.io.ObjectOutputStream;
028 import java.io.Serializable;
029 import java.util.Comparator;
030 import java.util.ConcurrentModificationException;
031 import java.util.Iterator;
032
033 import javax.annotation.Nullable;
034
035 import com.google.common.annotations.GwtCompatible;
036 import com.google.common.annotations.GwtIncompatible;
037 import com.google.common.primitives.Ints;
038
039 /**
040 * A multiset which maintains the ordering of its elements, according to either
041 * their natural order or an explicit {@link Comparator}. In all cases, this
042 * implementation uses {@link Comparable#compareTo} or {@link
043 * Comparator#compare} instead of {@link Object#equals} to determine
044 * equivalence of instances.
045 *
046 * <p><b>Warning:</b> The comparison must be <i>consistent with equals</i> as
047 * explained by the {@link Comparable} class specification. Otherwise, the
048 * resulting multiset will violate the {@link java.util.Collection} contract,
049 * which is specified in terms of {@link Object#equals}.
050 *
051 * @author Louis Wasserman
052 * @author Jared Levy
053 * @since 2.0 (imported from Google Collections Library)
054 */
055 @GwtCompatible(emulated = true)
056 public final class TreeMultiset<E> extends AbstractSortedMultiset<E>
057 implements Serializable {
058
059 /**
060 * Creates a new, empty multiset, sorted according to the elements' natural
061 * order. All elements inserted into the multiset must implement the
062 * {@code Comparable} interface. Furthermore, all such elements must be
063 * <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a
064 * {@code ClassCastException} for any elements {@code e1} and {@code e2} in
065 * the multiset. If the user attempts to add an element to the multiset that
066 * violates this constraint (for example, the user attempts to add a string
067 * element to a set whose elements are integers), the {@code add(Object)}
068 * call will throw a {@code ClassCastException}.
069 *
070 * <p>The type specification is {@code <E extends Comparable>}, instead of the
071 * more specific {@code <E extends Comparable<? super E>>}, to support
072 * classes defined without generics.
073 */
074 public static <E extends Comparable> TreeMultiset<E> create() {
075 return new TreeMultiset<E>(Ordering.natural());
076 }
077
078 /**
079 * Creates a new, empty multiset, sorted according to the specified
080 * comparator. All elements inserted into the multiset must be <i>mutually
081 * comparable</i> by the specified comparator: {@code comparator.compare(e1,
082 * e2)} must not throw a {@code ClassCastException} for any elements {@code
083 * e1} and {@code e2} in the multiset. If the user attempts to add an element
084 * to the multiset that violates this constraint, the {@code add(Object)} call
085 * will throw a {@code ClassCastException}.
086 *
087 * @param comparator the comparator that will be used to sort this multiset. A
088 * null value indicates that the elements' <i>natural ordering</i> should
089 * be used.
090 */
091 @SuppressWarnings("unchecked")
092 public static <E> TreeMultiset<E> create(
093 @Nullable Comparator<? super E> comparator) {
094 return (comparator == null)
095 ? new TreeMultiset<E>((Comparator) Ordering.natural())
096 : new TreeMultiset<E>(comparator);
097 }
098
099 /**
100 * Creates an empty multiset containing the given initial elements, sorted
101 * according to the elements' natural order.
102 *
103 * <p>This implementation is highly efficient when {@code elements} is itself
104 * a {@link Multiset}.
105 *
106 * <p>The type specification is {@code <E extends Comparable>}, instead of the
107 * more specific {@code <E extends Comparable<? super E>>}, to support
108 * classes defined without generics.
109 */
110 public static <E extends Comparable> TreeMultiset<E> create(
111 Iterable<? extends E> elements) {
112 TreeMultiset<E> multiset = create();
113 Iterables.addAll(multiset, elements);
114 return multiset;
115 }
116
117 /**
118 * Returns an iterator over the elements contained in this collection.
119 */
120 @Override
121 public Iterator<E> iterator() {
122 // Needed to avoid Javadoc bug.
123 return super.iterator();
124 }
125
126 private TreeMultiset(Comparator<? super E> comparator) {
127 super(comparator);
128 this.range = GeneralRange.all(comparator);
129 this.rootReference = new Reference<Node<E>>();
130 }
131
132 private TreeMultiset(GeneralRange<E> range, Reference<Node<E>> root) {
133 super(range.comparator());
134 this.range = range;
135 this.rootReference = root;
136 }
137
138 @SuppressWarnings("unchecked")
139 E checkElement(Object o) {
140 return (E) o;
141 }
142
143 private transient final GeneralRange<E> range;
144
145 private transient final Reference<Node<E>> rootReference;
146
147 static final class Reference<T> {
148 T value;
149
150 public Reference() {}
151
152 public T get() {
153 return value;
154 }
155
156 public boolean compareAndSet(T expected, T newValue) {
157 if (value == expected) {
158 value = newValue;
159 return true;
160 }
161 return false;
162 }
163 }
164
165 @Override
166 int distinctElements() {
167 Node<E> root = rootReference.get();
168 return Ints.checkedCast(BstRangeOps.totalInRange(distinctAggregate(), range, root));
169 }
170
171 @Override
172 public int size() {
173 Node<E> root = rootReference.get();
174 return Ints.saturatedCast(BstRangeOps.totalInRange(sizeAggregate(), range, root));
175 }
176
177 @Override
178 public int count(@Nullable Object element) {
179 try {
180 E e = checkElement(element);
181 if (range.contains(e)) {
182 Node<E> node = BstOperations.seek(comparator(), rootReference.get(), e);
183 return countOrZero(node);
184 }
185 return 0;
186 } catch (ClassCastException e) {
187 return 0;
188 } catch (NullPointerException e) {
189 return 0;
190 }
191 }
192
193 private int mutate(@Nullable E e, MultisetModifier modifier) {
194 BstMutationRule<E, Node<E>> mutationRule = BstMutationRule.createRule(
195 modifier,
196 BstCountBasedBalancePolicies.
197 <E, Node<E>>singleRebalancePolicy(distinctAggregate()),
198 nodeFactory());
199 BstMutationResult<E, Node<E>> mutationResult =
200 BstOperations.mutate(comparator(), mutationRule, rootReference.get(), e);
201 if (!rootReference.compareAndSet(
202 mutationResult.getOriginalRoot(), mutationResult.getChangedRoot())) {
203 throw new ConcurrentModificationException();
204 }
205 Node<E> original = mutationResult.getOriginalTarget();
206 return countOrZero(original);
207 }
208
209 @Override
210 public int add(E element, int occurrences) {
211 checkElement(element);
212 if (occurrences == 0) {
213 return count(element);
214 }
215 checkArgument(range.contains(element));
216 return mutate(element, new AddModifier(occurrences));
217 }
218
219 @Override
220 public int remove(@Nullable Object element, int occurrences) {
221 if (element == null) {
222 return 0;
223 } else if (occurrences == 0) {
224 return count(element);
225 }
226 try {
227 E e = checkElement(element);
228 return range.contains(e) ? mutate(e, new RemoveModifier(occurrences)) : 0;
229 } catch (ClassCastException e) {
230 return 0;
231 }
232 }
233
234 @Override
235 public boolean setCount(E element, int oldCount, int newCount) {
236 checkElement(element);
237 checkArgument(range.contains(element));
238 return mutate(element, new ConditionalSetCountModifier(oldCount, newCount))
239 == oldCount;
240 }
241
242 @Override
243 public int setCount(E element, int count) {
244 checkElement(element);
245 checkArgument(range.contains(element));
246 return mutate(element, new SetCountModifier(count));
247 }
248
249 private BstPathFactory<Node<E>, BstInOrderPath<Node<E>>> pathFactory() {
250 return BstInOrderPath.inOrderFactory();
251 }
252
253 @Override
254 Iterator<Entry<E>> entryIterator() {
255 Node<E> root = rootReference.get();
256 final BstInOrderPath<Node<E>> startingPath =
257 BstRangeOps.furthestPath(range, LEFT, pathFactory(), root);
258 return iteratorInDirection(startingPath, RIGHT);
259 }
260
261 @Override
262 Iterator<Entry<E>> descendingEntryIterator() {
263 Node<E> root = rootReference.get();
264 final BstInOrderPath<Node<E>> startingPath =
265 BstRangeOps.furthestPath(range, RIGHT, pathFactory(), root);
266 return iteratorInDirection(startingPath, LEFT);
267 }
268
269 private Iterator<Entry<E>> iteratorInDirection(
270 @Nullable BstInOrderPath<Node<E>> start, final BstSide direction) {
271 final Iterator<BstInOrderPath<Node<E>>> pathIterator =
272 new AbstractLinkedIterator<BstInOrderPath<Node<E>>>(start) {
273 @Override
274 protected BstInOrderPath<Node<E>> computeNext(BstInOrderPath<Node<E>> previous) {
275 if (!previous.hasNext(direction)) {
276 return null;
277 }
278 BstInOrderPath<Node<E>> next = previous.next(direction);
279 // TODO(user): only check against one side
280 return range.contains(next.getTip().getKey()) ? next : null;
281 }
282 };
283 return new Iterator<Entry<E>>() {
284 E toRemove = null;
285
286 @Override
287 public boolean hasNext() {
288 return pathIterator.hasNext();
289 }
290
291 @Override
292 public Entry<E> next() {
293 BstInOrderPath<Node<E>> path = pathIterator.next();
294 return new LiveEntry(
295 toRemove = path.getTip().getKey(), path.getTip().elemCount());
296 }
297
298 @Override
299 public void remove() {
300 checkState(toRemove != null);
301 setCount(toRemove, 0);
302 toRemove = null;
303 }
304 };
305 }
306
307 class LiveEntry extends Multisets.AbstractEntry<E> {
308 private Node<E> expectedRoot;
309 private final E element;
310 private int count;
311
312 private LiveEntry(E element, int count) {
313 this.expectedRoot = rootReference.get();
314 this.element = element;
315 this.count = count;
316 }
317
318 @Override
319 public E getElement() {
320 return element;
321 }
322
323 @Override
324 public int getCount() {
325 if (rootReference.get() == expectedRoot) {
326 return count;
327 } else {
328 // check for updates
329 expectedRoot = rootReference.get();
330 return count = TreeMultiset.this.count(element);
331 }
332 }
333 }
334
335 @Override
336 public void clear() {
337 Node<E> root = rootReference.get();
338 Node<E> cleared = BstRangeOps.minusRange(range,
339 BstCountBasedBalancePolicies.<E, Node<E>>fullRebalancePolicy(distinctAggregate()),
340 nodeFactory(), root);
341 if (!rootReference.compareAndSet(root, cleared)) {
342 throw new ConcurrentModificationException();
343 }
344 }
345
346 @Override
347 public SortedMultiset<E> headMultiset(E upperBound, BoundType boundType) {
348 checkNotNull(upperBound);
349 return new TreeMultiset<E>(
350 range.intersect(GeneralRange.upTo(comparator, upperBound, boundType)), rootReference);
351 }
352
353 @Override
354 public SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType) {
355 checkNotNull(lowerBound);
356 return new TreeMultiset<E>(
357 range.intersect(GeneralRange.downTo(comparator, lowerBound, boundType)), rootReference);
358 }
359
360 /**
361 * {@inheritDoc}
362 *
363 * @since 11.0
364 */
365 @Override
366 public Comparator<? super E> comparator() {
367 return super.comparator();
368 }
369
370 private static final class Node<E> extends BstNode<E, Node<E>> implements Serializable {
371 private final long size;
372 private final int distinct;
373
374 private Node(E key, int elemCount, @Nullable Node<E> left,
375 @Nullable Node<E> right) {
376 super(key, left, right);
377 checkArgument(elemCount > 0);
378 this.size = (long) elemCount + sizeOrZero(left) + sizeOrZero(right);
379 this.distinct = 1 + distinctOrZero(left) + distinctOrZero(right);
380 }
381
382 int elemCount() {
383 long result = size - sizeOrZero(childOrNull(LEFT))
384 - sizeOrZero(childOrNull(RIGHT));
385 return Ints.checkedCast(result);
386 }
387
388 private Node(E key, int elemCount) {
389 this(key, elemCount, null, null);
390 }
391
392 private static final long serialVersionUID = 0;
393 }
394
395 private static long sizeOrZero(@Nullable Node<?> node) {
396 return (node == null) ? 0 : node.size;
397 }
398
399 private static int distinctOrZero(@Nullable Node<?> node) {
400 return (node == null) ? 0 : node.distinct;
401 }
402
403 private static int countOrZero(@Nullable Node<?> entry) {
404 return (entry == null) ? 0 : entry.elemCount();
405 }
406
407 @SuppressWarnings("unchecked")
408 private BstAggregate<Node<E>> distinctAggregate() {
409 return (BstAggregate) DISTINCT_AGGREGATE;
410 }
411
412 private static final BstAggregate<Node<Object>> DISTINCT_AGGREGATE =
413 new BstAggregate<Node<Object>>() {
414 @Override
415 public int entryValue(Node<Object> entry) {
416 return 1;
417 }
418
419 @Override
420 public long treeValue(@Nullable Node<Object> tree) {
421 return distinctOrZero(tree);
422 }
423 };
424
425 @SuppressWarnings("unchecked")
426 private BstAggregate<Node<E>> sizeAggregate() {
427 return (BstAggregate) SIZE_AGGREGATE;
428 }
429
430 private static final BstAggregate<Node<Object>> SIZE_AGGREGATE =
431 new BstAggregate<Node<Object>>() {
432 @Override
433 public int entryValue(Node<Object> entry) {
434 return entry.elemCount();
435 }
436
437 @Override
438 public long treeValue(@Nullable Node<Object> tree) {
439 return sizeOrZero(tree);
440 }
441 };
442
443 @SuppressWarnings("unchecked")
444 private BstNodeFactory<Node<E>> nodeFactory() {
445 return (BstNodeFactory) NODE_FACTORY;
446 }
447
448 private static final BstNodeFactory<Node<Object>> NODE_FACTORY =
449 new BstNodeFactory<Node<Object>>() {
450 @Override
451 public Node<Object> createNode(Node<Object> source, @Nullable Node<Object> left,
452 @Nullable Node<Object> right) {
453 return new Node<Object>(source.getKey(), source.elemCount(), left, right);
454 }
455 };
456
457 private abstract class MultisetModifier implements BstModifier<E, Node<E>> {
458 abstract int newCount(int oldCount);
459
460 @Nullable
461 @Override
462 public BstModificationResult<Node<E>> modify(E key, @Nullable Node<E> originalEntry) {
463 int oldCount = countOrZero(originalEntry);
464 int newCount = newCount(oldCount);
465 if (oldCount == newCount) {
466 return BstModificationResult.identity(originalEntry);
467 } else if (newCount == 0) {
468 return BstModificationResult.rebalancingChange(originalEntry, null);
469 } else if (oldCount == 0) {
470 return BstModificationResult.rebalancingChange(null, new Node<E>(key, newCount));
471 } else {
472 return BstModificationResult.rebuildingChange(originalEntry,
473 new Node<E>(originalEntry.getKey(), newCount));
474 }
475 }
476 }
477
478 private final class AddModifier extends MultisetModifier {
479 private final int countToAdd;
480
481 private AddModifier(int countToAdd) {
482 checkArgument(countToAdd > 0);
483 this.countToAdd = countToAdd;
484 }
485
486 @Override
487 int newCount(int oldCount) {
488 checkArgument(countToAdd <= Integer.MAX_VALUE - oldCount, "Cannot add this many elements");
489 return oldCount + countToAdd;
490 }
491 }
492
493 private final class RemoveModifier extends MultisetModifier {
494 private final int countToRemove;
495
496 private RemoveModifier(int countToRemove) {
497 checkArgument(countToRemove > 0);
498 this.countToRemove = countToRemove;
499 }
500
501 @Override
502 int newCount(int oldCount) {
503 return Math.max(0, oldCount - countToRemove);
504 }
505 }
506
507 private final class SetCountModifier extends MultisetModifier {
508 private final int countToSet;
509
510 private SetCountModifier(int countToSet) {
511 checkArgument(countToSet >= 0);
512 this.countToSet = countToSet;
513 }
514
515 @Override
516 int newCount(int oldCount) {
517 return countToSet;
518 }
519 }
520
521 private final class ConditionalSetCountModifier extends MultisetModifier {
522 private final int expectedCount;
523 private final int setCount;
524
525 private ConditionalSetCountModifier(int expectedCount, int setCount) {
526 checkArgument(setCount >= 0 & expectedCount >= 0);
527 this.expectedCount = expectedCount;
528 this.setCount = setCount;
529 }
530
531 @Override
532 int newCount(int oldCount) {
533 return (oldCount == expectedCount) ? setCount : oldCount;
534 }
535 }
536
537 /*
538 * TODO(jlevy): Decide whether entrySet() should return entries with an
539 * equals() method that calls the comparator to compare the two keys. If that
540 * change is made, AbstractMultiset.equals() can simply check whether two
541 * multisets have equal entry sets.
542 */
543
544 /**
545 * @serialData the comparator, the number of distinct elements, the first
546 * element, its count, the second element, its count, and so on
547 */
548 @GwtIncompatible("java.io.ObjectOutputStream")
549 private void writeObject(ObjectOutputStream stream) throws IOException {
550 stream.defaultWriteObject();
551 stream.writeObject(elementSet().comparator());
552 Serialization.writeMultiset(this, stream);
553 }
554
555 @GwtIncompatible("java.io.ObjectInputStream")
556 private void readObject(ObjectInputStream stream)
557 throws IOException, ClassNotFoundException {
558 stream.defaultReadObject();
559 @SuppressWarnings("unchecked") // reading data stored by writeObject
560 Comparator<? super E> comparator = (Comparator<? super E>) stream.readObject();
561 Serialization.getFieldSetter(AbstractSortedMultiset.class, "comparator").set(this, comparator);
562 Serialization.getFieldSetter(TreeMultiset.class, "range").set(this,
563 GeneralRange.all(comparator));
564 Serialization.getFieldSetter(TreeMultiset.class, "rootReference").set(this,
565 new Reference<Node<E>>());
566 Serialization.populateMultiset(this, stream);
567 }
568
569 @GwtIncompatible("not needed in emulated source")
570 private static final long serialVersionUID = 1;
571 }
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