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
015package com.google.common.collect;
016
017import static com.google.common.base.Preconditions.checkArgument;
018import static com.google.common.base.Preconditions.checkNotNull;
019
020import com.google.common.annotations.Beta;
021import com.google.common.annotations.GwtIncompatible;
022
023import java.io.Serializable;
024import java.util.Arrays;
025import java.util.Collection;
026import java.util.Collections;
027import java.util.Comparator;
028import java.util.Iterator;
029import 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")
082public 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  @Override
321  public final Comparator<? super E> comparator() {
322    return elementSet().comparator();
323  }
324
325  @Override
326  public abstract ImmutableSortedSet<E> elementSet();
327
328  transient ImmutableSortedMultiset<E> descendingMultiset;
329
330  @Override
331  public ImmutableSortedMultiset<E> descendingMultiset() {
332    ImmutableSortedMultiset<E> result = descendingMultiset;
333    if (result == null) {
334      return descendingMultiset = new DescendingImmutableSortedMultiset<E>(this);
335    }
336    return result;
337  }
338
339  /**
340   * {@inheritDoc}
341   *
342   * <p>This implementation is guaranteed to throw an {@link UnsupportedOperationException}.
343   *
344   * @throws UnsupportedOperationException always
345   * @deprecated Unsupported operation.
346   */
347  @Deprecated
348  @Override
349  public final Entry<E> pollFirstEntry() {
350    throw new UnsupportedOperationException();
351  }
352
353  /**
354   * {@inheritDoc}
355   *
356   * <p>This implementation is guaranteed to throw an {@link UnsupportedOperationException}.
357   *
358   * @throws UnsupportedOperationException always
359   * @deprecated Unsupported operation.
360   */
361  @Deprecated
362  @Override
363  public final Entry<E> pollLastEntry() {
364    throw new UnsupportedOperationException();
365  }
366
367  @Override
368  public abstract ImmutableSortedMultiset<E> headMultiset(E upperBound, BoundType boundType);
369
370  @Override
371  public ImmutableSortedMultiset<E> subMultiset(
372      E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType) {
373    checkArgument(comparator().compare(lowerBound, upperBound) <= 0,
374        "Expected lowerBound <= upperBound but %s > %s", lowerBound, upperBound);
375    return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
376  }
377
378  @Override
379  public abstract ImmutableSortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);
380
381  /**
382   * Returns a builder that creates immutable sorted multisets with an explicit comparator. If the
383   * comparator has a more general type than the set being generated, such as creating a {@code
384   * SortedMultiset<Integer>} with a {@code Comparator<Number>}, use the {@link Builder}
385   * constructor instead.
386   *
387   * @throws NullPointerException if {@code comparator} is null
388   */
389  public static <E> Builder<E> orderedBy(Comparator<E> comparator) {
390    return new Builder<E>(comparator);
391  }
392
393  /**
394   * Returns a builder that creates immutable sorted multisets whose elements are ordered by the
395   * reverse of their natural ordering.
396   *
397   * <p>Note: the type parameter {@code E} extends {@code Comparable<E>} rather than {@code
398   * Comparable<? super E>} as a workaround for javac <a
399   * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6468354">bug 6468354</a>.
400   */
401  public static <E extends Comparable<E>> Builder<E> reverseOrder() {
402    return new Builder<E>(Ordering.natural().reverse());
403  }
404
405  /**
406   * Returns a builder that creates immutable sorted multisets whose elements are ordered by their
407   * natural ordering. The sorted multisets use {@link Ordering#natural()} as the comparator. This
408   * method provides more type-safety than {@link #builder}, as it can be called only for classes
409   * that implement {@link Comparable}.
410   *
411   * <p>Note: the type parameter {@code E} extends {@code Comparable<E>} rather than {@code
412   * Comparable<? super E>} as a workaround for javac <a
413   * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6468354">bug 6468354</a>.
414   */
415  public static <E extends Comparable<E>> Builder<E> naturalOrder() {
416    return new Builder<E>(Ordering.natural());
417  }
418
419  /**
420   * A builder for creating immutable multiset instances, especially {@code public static final}
421   * multisets ("constant multisets"). Example:
422   *
423   * <pre> {@code
424   *
425   *   public static final ImmutableSortedMultiset<Bean> BEANS =
426   *       new ImmutableSortedMultiset.Builder<Bean>()
427   *           .addCopies(Bean.COCOA, 4)
428   *           .addCopies(Bean.GARDEN, 6)
429   *           .addCopies(Bean.RED, 8)
430   *           .addCopies(Bean.BLACK_EYED, 10)
431   *           .build();}</pre>
432   *
433   * Builder instances can be reused; it is safe to call {@link #build} multiple times to build
434   * multiple multisets in series.
435   *
436   * @since 12.0
437   */
438  public static class Builder<E> extends ImmutableMultiset.Builder<E> {
439    private final Comparator<? super E> comparator;
440
441    /**
442     * Creates a new builder. The returned builder is equivalent to the builder generated by
443     * {@link ImmutableSortedMultiset#orderedBy(Comparator)}.
444     */
445    public Builder(Comparator<? super E> comparator) {
446      super(TreeMultiset.<E>create(comparator));
447      this.comparator = checkNotNull(comparator);
448    }
449
450    /**
451     * Adds {@code element} to the {@code ImmutableSortedMultiset}.
452     *
453     * @param element the element to add
454     * @return this {@code Builder} object
455     * @throws NullPointerException if {@code element} is null
456     */
457    @Override
458    public Builder<E> add(E element) {
459      super.add(element);
460      return this;
461    }
462
463    /**
464     * Adds a number of occurrences of an element to this {@code ImmutableSortedMultiset}.
465     *
466     * @param element the element to add
467     * @param occurrences the number of occurrences of the element to add. May be zero, in which
468     *        case no change will be made.
469     * @return this {@code Builder} object
470     * @throws NullPointerException if {@code element} is null
471     * @throws IllegalArgumentException if {@code occurrences} is negative, or if this operation
472     *         would result in more than {@link Integer#MAX_VALUE} occurrences of the element
473     */
474    @Override
475    public Builder<E> addCopies(E element, int occurrences) {
476      super.addCopies(element, occurrences);
477      return this;
478    }
479
480    /**
481     * Adds or removes the necessary occurrences of an element such that the element attains the
482     * desired count.
483     *
484     * @param element the element to add or remove occurrences of
485     * @param count the desired count of the element in this multiset
486     * @return this {@code Builder} object
487     * @throws NullPointerException if {@code element} is null
488     * @throws IllegalArgumentException if {@code count} is negative
489     */
490    @Override
491    public Builder<E> setCount(E element, int count) {
492      super.setCount(element, count);
493      return this;
494    }
495
496    /**
497     * Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
498     *
499     * @param elements the elements to add
500     * @return this {@code Builder} object
501     * @throws NullPointerException if {@code elements} is null or contains a null element
502     */
503    @Override
504    public Builder<E> add(E... elements) {
505      super.add(elements);
506      return this;
507    }
508
509    /**
510     * Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
511     *
512     * @param elements the {@code Iterable} to add to the {@code ImmutableSortedMultiset}
513     * @return this {@code Builder} object
514     * @throws NullPointerException if {@code elements} is null or contains a null element
515     */
516    @Override
517    public Builder<E> addAll(Iterable<? extends E> elements) {
518      super.addAll(elements);
519      return this;
520    }
521
522    /**
523     * Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
524     *
525     * @param elements the elements to add to the {@code ImmutableSortedMultiset}
526     * @return this {@code Builder} object
527     * @throws NullPointerException if {@code elements} is null or contains a null element
528     */
529    @Override
530    public Builder<E> addAll(Iterator<? extends E> elements) {
531      super.addAll(elements);
532      return this;
533    }
534
535    /**
536     * Returns a newly-created {@code ImmutableSortedMultiset} based on the contents of the {@code
537     * Builder}.
538     */
539    @Override
540    public ImmutableSortedMultiset<E> build() {
541      return copyOfSorted((SortedMultiset<E>) contents);
542    }
543  }
544
545  private static final class SerializedForm implements Serializable {
546    Comparator comparator;
547    Object[] elements;
548    int[] counts;
549
550    SerializedForm(SortedMultiset<?> multiset) {
551      this.comparator = multiset.comparator();
552      int n = multiset.entrySet().size();
553      elements = new Object[n];
554      counts = new int[n];
555      int i = 0;
556      for (Entry<?> entry : multiset.entrySet()) {
557        elements[i] = entry.getElement();
558        counts[i] = entry.getCount();
559        i++;
560      }
561    }
562
563    @SuppressWarnings("unchecked")
564    Object readResolve() {
565      int n = elements.length;
566      Builder<Object> builder = orderedBy(comparator);
567      for (int i = 0; i < n; i++) {
568        builder.addCopies(elements[i], counts[i]);
569      }
570      return builder.build();
571    }
572  }
573
574  @Override
575  Object writeReplace() {
576    return new SerializedForm(this);
577  }
578}