com.google.common.collect.TreeMultiset Maven / Gradle / Ivy
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/*
* Copyright (C) 2007 Google Inc.
*
* 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 com.google.common.annotations.GwtCompatible;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Comparator;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.Collection;
import java.util.concurrent.atomic.AtomicInteger;
import javax.annotation.Nullable;
/**
* A multiset which maintains the ordering of its elements, according to either
* their natural order or an explicit {@link Comparator}. In all cases, this
* implementation uses {@link Comparable#compareTo} or {@link
* Comparator#compare} instead of {@link Object#equals} to determine
* equivalence of instances.
*
* Warning: The comparison must be consistent with equals as
* explained by the {@link Comparable} class specification. Otherwise, the
* resulting multiset will violate the {@link Collection} contract, which it is
* specified in terms of {@link Object#equals}.
*
* @author Neal Kanodia
* @author Jared Levy
*/
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public final class TreeMultiset extends AbstractMapBasedMultiset {
/**
* Creates a new, empty multiset, sorted according to the elements' natural
* order. All elements inserted into the multiset must implement the
* {@code Comparable} interface. Furthermore, all such elements must be
* mutually comparable: {@code e1.compareTo(e2)} must not throw a
* {@code ClassCastException} for any elements {@code e1} and {@code e2} in
* the multiset. If the user attempts to add an element to the multiset that
* violates this constraint (for example, the user attempts to add a string
* element to a set whose elements are integers), the {@code add(Object)}
* call will throw a {@code ClassCastException}.
*
* The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*/
@SuppressWarnings("unchecked") // eclipse doesn't like the raw Comparable
public static TreeMultiset create() {
return new TreeMultiset();
}
/**
* Creates a new, empty multiset, sorted according to the specified
* comparator. All elements inserted into the multiset must be mutually
* comparable by the specified comparator: {@code comparator.compare(e1,
* e2)} must not throw a {@code ClassCastException} for any elements {@code
* e1} and {@code e2} in the multiset. If the user attempts to add an element
* to the multiset that violates this constraint, the {@code add(Object)} call
* will throw a {@code ClassCastException}.
*
* @param comparator the comparator that will be used to sort this multiset. A
* null value indicates that the elements' natural ordering should
* be used.
*/
public static TreeMultiset create(Comparator comparator) {
return new TreeMultiset(comparator);
}
/**
* Creates an empty multiset containing the given initial elements, sorted
* according to the elements' natural order.
*
* The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*/
@SuppressWarnings("unchecked") // eclipse doesn't like the raw Comparable
public static TreeMultiset create(
Iterable elements) {
TreeMultiset multiset = create();
Iterables.addAll(multiset, elements);
return multiset;
}
private TreeMultiset() {
super(new TreeMap());
}
private TreeMultiset(Comparator comparator) {
super(new TreeMap(comparator));
}
/**
* {@inheritDoc}
*
* In {@code TreeMultiset}, the return type of this method is narrowed
* from {@link Set} to {@link SortedSet}.
*/
@Override public SortedSet elementSet() {
return (SortedSet) super.elementSet();
}
@Override public int count(@Nullable Object element) {
try {
return super.count(element);
} catch (NullPointerException e) {
return 0;
} catch (ClassCastException e) {
return 0;
}
}
@Override Set createElementSet() {
return new SortedMapBasedElementSet(
(SortedMap) backingMap());
}
private class SortedMapBasedElementSet extends MapBasedElementSet
implements SortedSet {
SortedMapBasedElementSet(SortedMap map) {
super(map);
}
SortedMap sortedMap() {
return (SortedMap) getMap();
}
public Comparator comparator() {
return sortedMap().comparator();
}
public E first() {
return sortedMap().firstKey();
}
public E last() {
return sortedMap().lastKey();
}
public SortedSet headSet(E toElement) {
return new SortedMapBasedElementSet(sortedMap().headMap(toElement));
}
public SortedSet subSet(E fromElement, E toElement) {
return new SortedMapBasedElementSet(
sortedMap().subMap(fromElement, toElement));
}
public SortedSet tailSet(E fromElement) {
return new SortedMapBasedElementSet(sortedMap().tailMap(fromElement));
}
@Override public boolean remove(Object element) {
try {
return super.remove(element);
} catch (NullPointerException e) {
return false;
} catch (ClassCastException e) {
return false;
}
}
}
/*
* TODO: Decide whether entrySet() should return entries with an equals()
* method that calls the comparator to compare the two keys. If that change
* is made, AbstractMultiset.equals() can simply check whether two multisets
* have equal entry sets.
*/
/**
* @serialData the comparator, the number of distinct elements, the first
* element, its count, the second element, its count, and so on
*/
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeObject(elementSet().comparator());
Serialization.writeMultiset(this, stream);
}
private void readObject(ObjectInputStream stream)
throws IOException, ClassNotFoundException {
stream.defaultReadObject();
@SuppressWarnings("unchecked") // reading data stored by writeObject
Comparator comparator
= (Comparator) stream.readObject();
setBackingMap(new TreeMap(comparator));
Serialization.populateMultiset(this, stream);
}
private static final long serialVersionUID = 0;
}