com.google.common.collect.Multisets Maven / Gradle / Ivy
/*
* 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import com.google.common.collect.Multiset.Entry;
import com.google.common.primitives.Ints;
import java.io.Serializable;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedSet;
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) {
return new UnmodifiableSortedMultiset(checkNotNull(sortedMultiset));
}
private static final class UnmodifiableSortedMultiset
extends UnmodifiableMultiset implements SortedMultiset {
private UnmodifiableSortedMultiset(SortedMultiset delegate) {
super(delegate);
}
@Override
protected SortedMultiset delegate() {
return (SortedMultiset) super.delegate();
}
@Override
public Comparator comparator() {
return delegate().comparator();
}
@Override
SortedSet createElementSet() {
return Collections.unmodifiableSortedSet(delegate().elementSet());
}
@Override
public SortedSet elementSet() {
return (SortedSet) super.elementSet();
}
private transient UnmodifiableSortedMultiset descendingMultiset;
@Override
public SortedMultiset descendingMultiset() {
UnmodifiableSortedMultiset result = descendingMultiset;
if (result == null) {
result = new UnmodifiableSortedMultiset(
delegate().descendingMultiset());
result.descendingMultiset = this;
return descendingMultiset = result;
}
return result;
}
@Override
public Entry firstEntry() {
return delegate().firstEntry();
}
@Override
public Entry lastEntry() {
return delegate().lastEntry();
}
@Override
public Entry pollFirstEntry() {
throw new UnsupportedOperationException();
}
@Override
public Entry pollLastEntry() {
throw new UnsupportedOperationException();
}
@Override
public SortedMultiset headMultiset(E upperBound, BoundType boundType) {
return unmodifiableSortedMultiset(
delegate().headMultiset(upperBound, boundType));
}
@Override
public SortedMultiset subMultiset(
E lowerBound, BoundType lowerBoundType,
E upperBound, BoundType upperBoundType) {
return unmodifiableSortedMultiset(delegate().subMultiset(
lowerBound, lowerBoundType, upperBound, upperBoundType));
}
@Override
public SortedMultiset tailMultiset(E lowerBound, BoundType boundType) {
return unmodifiableSortedMultiset(
delegate().tailMultiset(lowerBound, boundType));
}
private static final long serialVersionUID = 0;
}
/**
* 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;
checkArgument(count >= 0);
}
@Override
@Nullable public E getElement() {
return element;
}
@Override
public int getCount() {
return count;
}
private static final long serialVersionUID = 0;
}
/**
* Returns a multiset view of the specified set. The multiset is backed by the
* set, so changes to the set are reflected in the multiset, and vice versa.
* If the set is modified while an iteration over the multiset is in progress
* (except through the iterator's own {@code remove} operation) the results of
* the iteration are undefined.
*
* The multiset supports element removal, which removes the corresponding
* element from the set. It does not support the {@code add} or {@code addAll}
* operations, nor does it support the use of {@code setCount} to add
* elements.
*
*
The returned multiset will be serializable if the specified set is
* serializable. The multiset is threadsafe if the set is threadsafe.
*
* @param set the backing set for the returned multiset view
*/
static Multiset forSet(Set set) {
return new SetMultiset(set);
}
/** @see Multisets#forSet */
private static class SetMultiset extends ForwardingCollection
implements Multiset, Serializable {
final Set delegate;
SetMultiset(Set set) {
delegate = checkNotNull(set);
}
@Override protected Set delegate() {
return delegate;
}
@Override
public int count(Object element) {
return delegate.contains(element) ? 1 : 0;
}
@Override
public int add(E element, int occurrences) {
throw new UnsupportedOperationException();
}
@Override
public int remove(Object element, int occurrences) {
if (occurrences == 0) {
return count(element);
}
checkArgument(occurrences > 0);
return delegate.remove(element) ? 1 : 0;
}
transient Set elementSet;
@Override
public Set elementSet() {
Set es = elementSet;
return (es == null) ? elementSet = new ElementSet() : es;
}
transient Set> entrySet;
@Override public Set> entrySet() {
Set> es = entrySet;
if (es == null) {
es = entrySet = new EntrySet() {
@Override Multiset multiset() {
return SetMultiset.this;
}
@Override public Iterator> iterator() {
return new TransformedIterator>(delegate.iterator()) {
@Override
Entry transform(E e) {
return Multisets.immutableEntry(e, 1);
}
};
}
@Override public int size() {
return delegate.size();
}
};
}
return es;
}
@Override public boolean add(E o) {
throw new UnsupportedOperationException();
}
@Override public boolean addAll(Collection c) {
throw new UnsupportedOperationException();
}
@Override
public int setCount(E element, int count) {
checkNonnegative(count, "count");
if (count == count(element)) {
return count;
} else if (count == 0) {
remove(element);
return 1;
} else {
throw new UnsupportedOperationException();
}
}
@Override
public boolean setCount(E element, int oldCount, int newCount) {
return setCountImpl(this, element, oldCount, newCount);
}
@Override public boolean equals(@Nullable Object object) {
if (object instanceof Multiset) {
Multiset that = (Multiset) object;
return this.size() == that.size() && delegate.equals(that.elementSet());
}
return false;
}
@Override public int hashCode() {
int sum = 0;
for (E e : this) {
sum += ((e == null) ? 0 : e.hashCode()) ^ 1;
}
return sum;
}
/** @see SetMultiset#elementSet */
class ElementSet extends ForwardingSet {
@Override protected Set delegate() {
return delegate;
}
@Override public boolean add(E o) {
throw new UnsupportedOperationException();
}
@Override public boolean addAll(Collection c) {
throw new UnsupportedOperationException();
}
}
private static final long serialVersionUID = 0;
}
/**
* 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 intersection of two multisets.
* An element's count in the multiset is the smaller of its counts in the two
* backing multisets. The iteration order of the returned multiset matches 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();
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 Multisets.immutableEntry(element, count);
}
}
return endOfData();
}
};
}
@Override
int distinctElements() {
return elementSet().size();
}
};
}
/**
* Returns {@code true} if {@code subMultiset.count(o) <=
* superMultiset.count(o)} for all {@code o}.
*
* @since 10.0
*/
@Beta
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
*/
@Beta 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 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 10.0
*/
@Beta public static boolean removeOccurrences(
Multiset multisetToModify, Multiset occurrencesToRemove) {
return removeOccurrencesImpl(multisetToModify, occurrencesToRemove);
}
/**
* Delegate that cares about the element types in occurrencesToRemove.
*/
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) {
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;
}
}
static abstract class ElementSet extends AbstractSet {
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();
}
}
static abstract class EntrySet extends AbstractSet>{
abstract Multiset multiset();
@Override public boolean contains(@Nullable Object o) {
if (o instanceof Entry) {
@SuppressWarnings("cast")
Entry entry = (Entry) o;
if (entry.getCount() <= 0) {
return false;
}
int count = multiset().count(entry.getElement());
return count == entry.getCount();
}
return false;
}
@SuppressWarnings("cast")
@Override public boolean remove(Object o) {
return contains(o)
&& multiset().elementSet().remove(((Entry) o).getElement());
}
@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() {
Iterators.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);
}
static void checkNonnegative(int count, String name) {
checkArgument(count >= 0, "%s cannot be negative: %s", name, count);
}
/**
* 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.sortedCopy(multiset.entrySet());
return ImmutableMultiset.copyFromEntries(sortedEntries);
}
}