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/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import static com.google.common.collect.CollectPreconditions.checkRemove;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.Multiset.Entry;
import com.google.common.primitives.Ints;

import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * Provides static utility methods for creating and working with {@link
 * Multiset} instances.
 *
 * 

See the Guava User Guide article on * {@code Multisets}. * * @author Kevin Bourrillion * @author Mike Bostock * @author Louis Wasserman * @since 2.0 (imported from Google Collections Library) */ @GwtCompatible public final class Multisets { private Multisets() {} /** * Returns an unmodifiable view of the specified multiset. Query operations on * the returned multiset "read through" to the specified multiset, and * attempts to modify the returned multiset result in an * {@link UnsupportedOperationException}. * *

The returned multiset will be serializable if the specified multiset is * serializable. * * @param multiset the multiset for which an unmodifiable view is to be * generated * @return an unmodifiable view of the multiset */ public static Multiset unmodifiableMultiset( Multiset multiset) { if (multiset instanceof UnmodifiableMultiset || multiset instanceof ImmutableMultiset) { // Since it's unmodifiable, the covariant cast is safe @SuppressWarnings("unchecked") Multiset result = (Multiset) multiset; return result; } return new UnmodifiableMultiset(checkNotNull(multiset)); } /** * Simply returns its argument. * * @deprecated no need to use this * @since 10.0 */ @Deprecated public static Multiset unmodifiableMultiset( ImmutableMultiset multiset) { return checkNotNull(multiset); } static class UnmodifiableMultiset extends ForwardingMultiset implements Serializable { final Multiset delegate; UnmodifiableMultiset(Multiset delegate) { this.delegate = delegate; } @SuppressWarnings("unchecked") @Override protected Multiset delegate() { // This is safe because all non-covariant methods are overriden return (Multiset) delegate; } transient Set elementSet; Set createElementSet() { return Collections.unmodifiableSet(delegate.elementSet()); } @Override public Set elementSet() { Set es = elementSet; return (es == null) ? elementSet = createElementSet() : es; } transient Set> entrySet; @SuppressWarnings("unchecked") @Override public Set> entrySet() { Set> es = entrySet; return (es == null) // Safe because the returned set is made unmodifiable and Entry // itself is readonly ? entrySet = (Set) Collections.unmodifiableSet(delegate.entrySet()) : es; } @SuppressWarnings("unchecked") @Override public Iterator iterator() { // Safe because the returned Iterator is made unmodifiable return (Iterator) Iterators.unmodifiableIterator(delegate.iterator()); } @Override public boolean add(E element) { throw new UnsupportedOperationException(); } @Override public int add(E element, int occurences) { throw new UnsupportedOperationException(); } @Override public boolean addAll(Collection elementsToAdd) { throw new UnsupportedOperationException(); } @Override public boolean remove(Object element) { throw new UnsupportedOperationException(); } @Override public int remove(Object element, int occurrences) { throw new UnsupportedOperationException(); } @Override public boolean removeAll(Collection elementsToRemove) { throw new UnsupportedOperationException(); } @Override public boolean retainAll(Collection elementsToRetain) { throw new UnsupportedOperationException(); } @Override public void clear() { throw new UnsupportedOperationException(); } @Override public int setCount(E element, int count) { throw new UnsupportedOperationException(); } @Override public boolean setCount(E element, int oldCount, int newCount) { throw new UnsupportedOperationException(); } private static final long serialVersionUID = 0; } /** * Returns an unmodifiable view of the specified sorted multiset. Query * operations on the returned multiset "read through" to the specified * multiset, and attempts to modify the returned multiset result in an {@link * UnsupportedOperationException}. * *

The returned multiset will be serializable if the specified multiset is * serializable. * * @param sortedMultiset the sorted multiset for which an unmodifiable view is * to be generated * @return an unmodifiable view of the multiset * @since 11.0 */ @Beta public static SortedMultiset unmodifiableSortedMultiset( SortedMultiset sortedMultiset) { // it's in its own file so it can be emulated for GWT return new UnmodifiableSortedMultiset(checkNotNull(sortedMultiset)); } /** * Returns an immutable multiset entry with the specified element and count. * The entry will be serializable if {@code e} is. * * @param e the element to be associated with the returned entry * @param n the count to be associated with the returned entry * @throws IllegalArgumentException if {@code n} is negative */ public static Multiset.Entry immutableEntry(@Nullable E e, int n) { return new ImmutableEntry(e, n); } static final class ImmutableEntry extends AbstractEntry implements Serializable { @Nullable final E element; final int count; ImmutableEntry(@Nullable E element, int count) { this.element = element; this.count = count; checkNonnegative(count, "count"); } @Override @Nullable public E getElement() { return element; } @Override public int getCount() { return count; } private static final long serialVersionUID = 0; } /** * Returns a view of the elements of {@code unfiltered} that satisfy a predicate. The returned * multiset is a live view of {@code unfiltered}; changes to one affect the other. * *

The resulting multiset's iterators, and those of its {@code entrySet()} and * {@code elementSet()}, do not support {@code remove()}. However, all other multiset methods * supported by {@code unfiltered} are supported by the returned multiset. When given an element * that doesn't satisfy the predicate, the multiset's {@code add()} and {@code addAll()} methods * throw an {@link IllegalArgumentException}. When methods such as {@code removeAll()} and * {@code clear()} are called on the filtered multiset, only elements that satisfy the filter * will be removed from the underlying multiset. * *

The returned multiset isn't threadsafe or serializable, even if {@code unfiltered} is. * *

Many of the filtered multiset's methods, such as {@code size()}, iterate across every * element in the underlying multiset and determine which elements satisfy the filter. When a * live view is not needed, it may be faster to copy the returned multiset and use the * copy. * *

Warning: {@code predicate} must be consistent with equals, as documented at * {@link Predicate#apply}. Do not provide a predicate such as * {@code Predicates.instanceOf(ArrayList.class)}, which is inconsistent with equals. (See * {@link Iterables#filter(Iterable, Class)} for related functionality.) * * @since 14.0 */ @Beta public static Multiset filter(Multiset unfiltered, Predicate predicate) { if (unfiltered instanceof FilteredMultiset) { // Support clear(), removeAll(), and retainAll() when filtering a filtered // collection. FilteredMultiset filtered = (FilteredMultiset) unfiltered; Predicate combinedPredicate = Predicates.and(filtered.predicate, predicate); return new FilteredMultiset(filtered.unfiltered, combinedPredicate); } return new FilteredMultiset(unfiltered, predicate); } private static final class FilteredMultiset extends AbstractMultiset { final Multiset unfiltered; final Predicate predicate; FilteredMultiset(Multiset unfiltered, Predicate predicate) { this.unfiltered = checkNotNull(unfiltered); this.predicate = checkNotNull(predicate); } @Override public UnmodifiableIterator iterator() { return Iterators.filter(unfiltered.iterator(), predicate); } @Override Set createElementSet() { return Sets.filter(unfiltered.elementSet(), predicate); } @Override Set> createEntrySet() { return Sets.filter(unfiltered.entrySet(), new Predicate>() { @Override public boolean apply(Entry entry) { return predicate.apply(entry.getElement()); } }); } @Override Iterator> entryIterator() { throw new AssertionError("should never be called"); } @Override int distinctElements() { return elementSet().size(); } @Override public int count(@Nullable Object element) { int count = unfiltered.count(element); if (count > 0) { @SuppressWarnings("unchecked") // element is equal to an E E e = (E) element; return predicate.apply(e) ? count : 0; } return 0; } @Override public int add(@Nullable E element, int occurrences) { checkArgument(predicate.apply(element), "Element %s does not match predicate %s", element, predicate); return unfiltered.add(element, occurrences); } @Override public int remove(@Nullable Object element, int occurrences) { checkNonnegative(occurrences, "occurrences"); if (occurrences == 0) { return count(element); } else { return contains(element) ? unfiltered.remove(element, occurrences) : 0; } } @Override public void clear() { elementSet().clear(); } } /** * Returns the expected number of distinct elements given the specified * elements. The number of distinct elements is only computed if {@code * elements} is an instance of {@code Multiset}; otherwise the default value * of 11 is returned. */ static int inferDistinctElements(Iterable elements) { if (elements instanceof Multiset) { return ((Multiset) elements).elementSet().size(); } return 11; // initial capacity will be rounded up to 16 } /** * Returns an unmodifiable view of the union of two multisets. * In the returned multiset, the count of each element is the maximum * of its counts in the two backing multisets. The iteration order of the * returned multiset matches that of the element set of {@code multiset1} * followed by the members of the element set of {@code multiset2} that are * not contained in {@code multiset1}, with repeated occurrences of the same * element appearing consecutively. * *

Results are undefined if {@code multiset1} and {@code multiset2} are * based on different equivalence relations (as {@code HashMultiset} and * {@code TreeMultiset} are). * * @since 14.0 */ @Beta public static Multiset union( final Multiset multiset1, final Multiset multiset2) { checkNotNull(multiset1); checkNotNull(multiset2); return new AbstractMultiset() { @Override public boolean contains(@Nullable Object element) { return multiset1.contains(element) || multiset2.contains(element); } @Override public boolean isEmpty() { return multiset1.isEmpty() && multiset2.isEmpty(); } @Override public int count(Object element) { return Math.max(multiset1.count(element), multiset2.count(element)); } @Override Set createElementSet() { return Sets.union(multiset1.elementSet(), multiset2.elementSet()); } @Override Iterator> entryIterator() { final Iterator> iterator1 = multiset1.entrySet().iterator(); final Iterator> iterator2 = multiset2.entrySet().iterator(); // TODO(user): consider making the entries live views return new AbstractIterator>() { @Override protected Entry computeNext() { if (iterator1.hasNext()) { Entry entry1 = iterator1.next(); E element = entry1.getElement(); int count = Math.max(entry1.getCount(), multiset2.count(element)); return immutableEntry(element, count); } while (iterator2.hasNext()) { Entry entry2 = iterator2.next(); E element = entry2.getElement(); if (!multiset1.contains(element)) { return immutableEntry(element, entry2.getCount()); } } return endOfData(); } }; } @Override int distinctElements() { return elementSet().size(); } }; } /** * Returns an unmodifiable view of the intersection of two multisets. * In the returned multiset, the count of each element is the minimum * of its counts in the two backing multisets, with elements that would have * a count of 0 not included. The iteration order of the returned multiset * matches that of the element set of {@code multiset1}, with repeated * occurrences of the same element appearing consecutively. * *

Results are undefined if {@code multiset1} and {@code multiset2} are * based on different equivalence relations (as {@code HashMultiset} and * {@code TreeMultiset} are). * * @since 2.0 */ public static Multiset intersection( final Multiset multiset1, final Multiset multiset2) { checkNotNull(multiset1); checkNotNull(multiset2); return new AbstractMultiset() { @Override public int count(Object element) { int count1 = multiset1.count(element); return (count1 == 0) ? 0 : Math.min(count1, multiset2.count(element)); } @Override Set createElementSet() { return Sets.intersection( multiset1.elementSet(), multiset2.elementSet()); } @Override Iterator> entryIterator() { final Iterator> iterator1 = multiset1.entrySet().iterator(); // TODO(user): consider making the entries live views return new AbstractIterator>() { @Override protected Entry computeNext() { while (iterator1.hasNext()) { Entry entry1 = iterator1.next(); E element = entry1.getElement(); int count = Math.min(entry1.getCount(), multiset2.count(element)); if (count > 0) { return immutableEntry(element, count); } } return endOfData(); } }; } @Override int distinctElements() { return elementSet().size(); } }; } /** * Returns an unmodifiable view of the sum of two multisets. * In the returned multiset, the count of each element is the sum of * its counts in the two backing multisets. The iteration order of the * returned multiset matches that of the element set of {@code multiset1} * followed by the members of the element set of {@code multiset2} that * are not contained in {@code multiset1}, with repeated occurrences of the * same element appearing consecutively. * *

Results are undefined if {@code multiset1} and {@code multiset2} are * based on different equivalence relations (as {@code HashMultiset} and * {@code TreeMultiset} are). * * @since 14.0 */ @Beta public static Multiset sum( final Multiset multiset1, final Multiset multiset2) { checkNotNull(multiset1); checkNotNull(multiset2); // TODO(user): consider making the entries live views return new AbstractMultiset() { @Override public boolean contains(@Nullable Object element) { return multiset1.contains(element) || multiset2.contains(element); } @Override public boolean isEmpty() { return multiset1.isEmpty() && multiset2.isEmpty(); } @Override public int size() { return multiset1.size() + multiset2.size(); } @Override public int count(Object element) { return multiset1.count(element) + multiset2.count(element); } @Override Set createElementSet() { return Sets.union(multiset1.elementSet(), multiset2.elementSet()); } @Override Iterator> entryIterator() { final Iterator> iterator1 = multiset1.entrySet().iterator(); final Iterator> iterator2 = multiset2.entrySet().iterator(); return new AbstractIterator>() { @Override protected Entry computeNext() { if (iterator1.hasNext()) { Entry entry1 = iterator1.next(); E element = entry1.getElement(); int count = entry1.getCount() + multiset2.count(element); return immutableEntry(element, count); } while (iterator2.hasNext()) { Entry entry2 = iterator2.next(); E element = entry2.getElement(); if (!multiset1.contains(element)) { return immutableEntry(element, entry2.getCount()); } } return endOfData(); } }; } @Override int distinctElements() { return elementSet().size(); } }; } /** * Returns an unmodifiable view of the difference of two multisets. * In the returned multiset, the count of each element is the result of the * zero-truncated subtraction of its count in the second multiset from * its count in the first multiset, with elements that would have a count of * 0 not included. The iteration order of the returned multiset matches that * of the element set of {@code multiset1}, with repeated occurrences of the * same element appearing consecutively. * *

Results are undefined if {@code multiset1} and {@code multiset2} are * based on different equivalence relations (as {@code HashMultiset} and * {@code TreeMultiset} are). * * @since 14.0 */ @Beta public static Multiset difference( final Multiset multiset1, final Multiset multiset2) { checkNotNull(multiset1); checkNotNull(multiset2); // TODO(user): consider making the entries live views return new AbstractMultiset() { @Override public int count(@Nullable Object element) { int count1 = multiset1.count(element); return (count1 == 0) ? 0 : Math.max(0, count1 - multiset2.count(element)); } @Override Iterator> entryIterator() { final Iterator> iterator1 = multiset1.entrySet().iterator(); return new AbstractIterator>() { @Override protected Entry computeNext() { while (iterator1.hasNext()) { Entry entry1 = iterator1.next(); E element = entry1.getElement(); int count = entry1.getCount() - multiset2.count(element); if (count > 0) { return immutableEntry(element, count); } } return endOfData(); } }; } @Override int distinctElements() { return Iterators.size(entryIterator()); } }; } /** * Returns {@code true} if {@code subMultiset.count(o) <= * superMultiset.count(o)} for all {@code o}. * * @since 10.0 */ public static boolean containsOccurrences( Multiset superMultiset, Multiset subMultiset) { checkNotNull(superMultiset); checkNotNull(subMultiset); for (Entry entry : subMultiset.entrySet()) { int superCount = superMultiset.count(entry.getElement()); if (superCount < entry.getCount()) { return false; } } return true; } /** * Modifies {@code multisetToModify} so that its count for an element * {@code e} is at most {@code multisetToRetain.count(e)}. * *

To be precise, {@code multisetToModify.count(e)} is set to * {@code Math.min(multisetToModify.count(e), * multisetToRetain.count(e))}. This is similar to * {@link #intersection(Multiset, Multiset) intersection} * {@code (multisetToModify, multisetToRetain)}, but mutates * {@code multisetToModify} instead of returning a view. * *

In contrast, {@code multisetToModify.retainAll(multisetToRetain)} keeps * all occurrences of elements that appear at all in {@code * multisetToRetain}, and deletes all occurrences of all other elements. * * @return {@code true} if {@code multisetToModify} was changed as a result * of this operation * @since 10.0 */ public static boolean retainOccurrences(Multiset multisetToModify, Multiset multisetToRetain) { return retainOccurrencesImpl(multisetToModify, multisetToRetain); } /** * Delegate implementation which cares about the element type. */ private static boolean retainOccurrencesImpl( Multiset multisetToModify, Multiset occurrencesToRetain) { checkNotNull(multisetToModify); checkNotNull(occurrencesToRetain); // Avoiding ConcurrentModificationExceptions is tricky. Iterator> entryIterator = multisetToModify.entrySet().iterator(); boolean changed = false; while (entryIterator.hasNext()) { Entry entry = entryIterator.next(); int retainCount = occurrencesToRetain.count(entry.getElement()); if (retainCount == 0) { entryIterator.remove(); changed = true; } else if (retainCount < entry.getCount()) { multisetToModify.setCount(entry.getElement(), retainCount); changed = true; } } return changed; } /** * For each occurrence of an element {@code e} in {@code occurrencesToRemove}, * removes one occurrence of {@code e} in {@code multisetToModify}. * *

Equivalently, this method modifies {@code multisetToModify} so that * {@code multisetToModify.count(e)} is set to * {@code Math.max(0, multisetToModify.count(e) - * occurrencesToRemove.count(e))}. * *

This is not the same as {@code multisetToModify.} * {@link Multiset#removeAll removeAll}{@code (occurrencesToRemove)}, which * removes all occurrences of elements that appear in * {@code occurrencesToRemove}. However, this operation is equivalent * to, albeit sometimes more efficient than, the following:

   {@code
   *
   *   for (E e : occurrencesToRemove) {
   *     multisetToModify.remove(e);
   *   }}
* * @return {@code true} if {@code multisetToModify} was changed as a result of * this operation * @since 18.0 (present in 10.0 with a requirement that the second parameter * be a {@code Multiset}) */ public static boolean removeOccurrences( Multiset multisetToModify, Iterable occurrencesToRemove) { if (occurrencesToRemove instanceof Multiset) { return removeOccurrencesImpl( multisetToModify, (Multiset) occurrencesToRemove); } else { return removeOccurrencesImpl(multisetToModify, occurrencesToRemove); } } private static boolean removeOccurrencesImpl( Multiset multisetToModify, Iterable occurrencesToRemove) { checkNotNull(multisetToModify); checkNotNull(occurrencesToRemove); boolean changed = false; for (Object o : occurrencesToRemove) { changed |= multisetToModify.remove(o); } return changed; } /** * Delegate that cares about the element types in multisetToModify. */ private static boolean removeOccurrencesImpl( Multiset multisetToModify, Multiset occurrencesToRemove) { // TODO(user): generalize to removing an Iterable, perhaps checkNotNull(multisetToModify); checkNotNull(occurrencesToRemove); boolean changed = false; Iterator> entryIterator = multisetToModify.entrySet().iterator(); while (entryIterator.hasNext()) { Entry entry = entryIterator.next(); int removeCount = occurrencesToRemove.count(entry.getElement()); if (removeCount >= entry.getCount()) { entryIterator.remove(); changed = true; } else if (removeCount > 0) { multisetToModify.remove(entry.getElement(), removeCount); changed = true; } } return changed; } /** * Implementation of the {@code equals}, {@code hashCode}, and * {@code toString} methods of {@link Multiset.Entry}. */ abstract static class AbstractEntry implements Multiset.Entry { /** * Indicates whether an object equals this entry, following the behavior * specified in {@link Multiset.Entry#equals}. */ @Override public boolean equals(@Nullable Object object) { if (object instanceof Multiset.Entry) { Multiset.Entry that = (Multiset.Entry) object; return this.getCount() == that.getCount() && Objects.equal(this.getElement(), that.getElement()); } return false; } /** * Return this entry's hash code, following the behavior specified in * {@link Multiset.Entry#hashCode}. */ @Override public int hashCode() { E e = getElement(); return ((e == null) ? 0 : e.hashCode()) ^ getCount(); } /** * Returns a string representation of this multiset entry. The string * representation consists of the associated element if the associated count * is one, and otherwise the associated element followed by the characters * " x " (space, x and space) followed by the count. Elements and counts are * converted to strings as by {@code String.valueOf}. */ @Override public String toString() { String text = String.valueOf(getElement()); int n = getCount(); return (n == 1) ? text : (text + " x " + n); } } /** * An implementation of {@link Multiset#equals}. */ static boolean equalsImpl(Multiset multiset, @Nullable Object object) { if (object == multiset) { return true; } if (object instanceof Multiset) { Multiset that = (Multiset) object; /* * We can't simply check whether the entry sets are equal, since that * approach fails when a TreeMultiset has a comparator that returns 0 * when passed unequal elements. */ if (multiset.size() != that.size() || multiset.entrySet().size() != that.entrySet().size()) { return false; } for (Entry entry : that.entrySet()) { if (multiset.count(entry.getElement()) != entry.getCount()) { return false; } } return true; } return false; } /** * An implementation of {@link Multiset#addAll}. */ static boolean addAllImpl( Multiset self, Collection elements) { if (elements.isEmpty()) { return false; } if (elements instanceof Multiset) { Multiset that = cast(elements); for (Entry entry : that.entrySet()) { self.add(entry.getElement(), entry.getCount()); } } else { Iterators.addAll(self, elements.iterator()); } return true; } /** * An implementation of {@link Multiset#removeAll}. */ static boolean removeAllImpl( Multiset self, Collection elementsToRemove) { Collection collection = (elementsToRemove instanceof Multiset) ? ((Multiset) elementsToRemove).elementSet() : elementsToRemove; return self.elementSet().removeAll(collection); } /** * An implementation of {@link Multiset#retainAll}. */ static boolean retainAllImpl( Multiset self, Collection elementsToRetain) { checkNotNull(elementsToRetain); Collection collection = (elementsToRetain instanceof Multiset) ? ((Multiset) elementsToRetain).elementSet() : elementsToRetain; return self.elementSet().retainAll(collection); } /** * An implementation of {@link Multiset#setCount(Object, int)}. */ static int setCountImpl(Multiset self, E element, int count) { checkNonnegative(count, "count"); int oldCount = self.count(element); int delta = count - oldCount; if (delta > 0) { self.add(element, delta); } else if (delta < 0) { self.remove(element, -delta); } return oldCount; } /** * An implementation of {@link Multiset#setCount(Object, int, int)}. */ static boolean setCountImpl( Multiset self, E element, int oldCount, int newCount) { checkNonnegative(oldCount, "oldCount"); checkNonnegative(newCount, "newCount"); if (self.count(element) == oldCount) { self.setCount(element, newCount); return true; } else { return false; } } abstract static class ElementSet extends Sets.ImprovedAbstractSet { abstract Multiset multiset(); @Override public void clear() { multiset().clear(); } @Override public boolean contains(Object o) { return multiset().contains(o); } @Override public boolean containsAll(Collection c) { return multiset().containsAll(c); } @Override public boolean isEmpty() { return multiset().isEmpty(); } @Override public Iterator iterator() { return new TransformedIterator, E>(multiset().entrySet().iterator()) { @Override E transform(Entry entry) { return entry.getElement(); } }; } @Override public boolean remove(Object o) { int count = multiset().count(o); if (count > 0) { multiset().remove(o, count); return true; } return false; } @Override public int size() { return multiset().entrySet().size(); } } abstract static class EntrySet extends Sets.ImprovedAbstractSet> { abstract Multiset multiset(); @Override public boolean contains(@Nullable Object o) { if (o instanceof Entry) { /* * The GWT compiler wrongly issues a warning here. */ @SuppressWarnings("cast") Entry entry = (Entry) o; if (entry.getCount() <= 0) { return false; } int count = multiset().count(entry.getElement()); return count == entry.getCount(); } return false; } // GWT compiler warning; see contains(). @SuppressWarnings("cast") @Override public boolean remove(Object object) { if (object instanceof Multiset.Entry) { Entry entry = (Entry) object; Object element = entry.getElement(); int entryCount = entry.getCount(); if (entryCount != 0) { // Safe as long as we never add a new entry, which we won't. @SuppressWarnings("unchecked") Multiset multiset = (Multiset) multiset(); return multiset.setCount(element, entryCount, 0); } } return false; } @Override public void clear() { multiset().clear(); } } /** * An implementation of {@link Multiset#iterator}. */ static Iterator iteratorImpl(Multiset multiset) { return new MultisetIteratorImpl( multiset, multiset.entrySet().iterator()); } static final class MultisetIteratorImpl implements Iterator { private final Multiset multiset; private final Iterator> entryIterator; private Entry currentEntry; /** Count of subsequent elements equal to current element */ private int laterCount; /** Count of all elements equal to current element */ private int totalCount; private boolean canRemove; MultisetIteratorImpl( Multiset multiset, Iterator> entryIterator) { this.multiset = multiset; this.entryIterator = entryIterator; } @Override public boolean hasNext() { return laterCount > 0 || entryIterator.hasNext(); } @Override public E next() { if (!hasNext()) { throw new NoSuchElementException(); } if (laterCount == 0) { currentEntry = entryIterator.next(); totalCount = laterCount = currentEntry.getCount(); } laterCount--; canRemove = true; return currentEntry.getElement(); } @Override public void remove() { checkRemove(canRemove); if (totalCount == 1) { entryIterator.remove(); } else { multiset.remove(currentEntry.getElement()); } totalCount--; canRemove = false; } } /** * An implementation of {@link Multiset#size}. */ static int sizeImpl(Multiset multiset) { long size = 0; for (Entry entry : multiset.entrySet()) { size += entry.getCount(); } return Ints.saturatedCast(size); } /** * Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557 */ static Multiset cast(Iterable iterable) { return (Multiset) iterable; } private static final Ordering> DECREASING_COUNT_ORDERING = new Ordering>() { @Override public int compare(Entry entry1, Entry entry2) { return Ints.compare(entry2.getCount(), entry1.getCount()); } }; /** * Returns a copy of {@code multiset} as an {@link ImmutableMultiset} whose iteration order is * highest count first, with ties broken by the iteration order of the original multiset. * * @since 11.0 */ @Beta public static ImmutableMultiset copyHighestCountFirst(Multiset multiset) { List> sortedEntries = Multisets.DECREASING_COUNT_ORDERING.immutableSortedCopy(multiset.entrySet()); return ImmutableMultiset.copyFromEntries(sortedEntries); } }