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 java.util.Comparator;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Multiset implementation backed by a TreeMap.
*
* @author Neal Kanodia
*/
public final class TreeMultiset extends AbstractMapBasedMultiset {
/**
* Constructs 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}.
*
* @see Comparable
* @see java.util.TreeSet
*/
public TreeMultiset() {
super(new TreeMap());
}
/**
* Constructs 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 TreeMultiset(Comparator comparator) {
super(new TreeMap(comparator));
}
/**
* Constructs an empty multiset containing the given initial elements, sorted
* according to the elements' natural order.
*/
public TreeMultiset(Iterable elements) {
this();
Iterables.addAll(this, elements); // careful if we make this class non-final
}
/**
* {@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 protected 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));
}
}
/*
* 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.
*/
private static final long serialVersionUID = 980261132547708887L;
}