001/*
002 * Copyright (C) 2011 The Guava Authors
003 * 
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
005 * use this file except in compliance with the License. You may obtain a copy of
006 * the License at
007 * 
008 * http://www.apache.org/licenses/LICENSE-2.0
009 * 
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
012 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
013 * License for the specific language governing permissions and limitations under
014 * the License.
015 */
016
017package com.google.common.collect;
018
019import com.google.common.annotations.Beta;
020import com.google.common.annotations.GwtCompatible;
021
022import java.util.Collection;
023import java.util.Comparator;
024import java.util.Iterator;
025import java.util.NavigableSet;
026
027/**
028 * A {@link Multiset} which maintains the ordering of its elements, according to
029 * either their natural order or an explicit {@link Comparator}. In all cases,
030 * this implementation uses {@link Comparable#compareTo} or
031 * {@link Comparator#compare} instead of {@link Object#equals} to determine
032 * equivalence of instances.
033 * 
034 * <p><b>Warning:</b> The comparison must be <i>consistent with equals</i> as
035 * explained by the {@link Comparable} class specification. Otherwise, the
036 * resulting multiset will violate the {@link Collection} contract, which it is
037 * specified in terms of {@link Object#equals}.
038 * 
039 * <p>See the Guava User Guide article on <a href=
040 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset">
041 * {@code Multiset}</a>.
042 * 
043 * @author Louis Wasserman
044 * @since 11.0
045 */
046@Beta
047@GwtCompatible(emulated = true)
048public interface SortedMultiset<E> extends SortedMultisetBridge<E>, SortedIterable<E> {
049  /**
050   * Returns the comparator that orders this multiset, or
051   * {@link Ordering#natural()} if the natural ordering of the elements is used.
052   */
053  Comparator<? super E> comparator();
054
055  /**
056   * Returns the entry of the first element in this multiset, or {@code null} if
057   * this multiset is empty.
058   */
059  Entry<E> firstEntry();
060
061  /**
062   * Returns the entry of the last element in this multiset, or {@code null} if
063   * this multiset is empty.
064   */
065  Entry<E> lastEntry();
066
067  /**
068   * Returns and removes the entry associated with the lowest element in this
069   * multiset, or returns {@code null} if this multiset is empty.
070   */
071  Entry<E> pollFirstEntry();
072
073  /**
074   * Returns and removes the entry associated with the greatest element in this
075   * multiset, or returns {@code null} if this multiset is empty.
076   */
077  Entry<E> pollLastEntry();
078
079  /**
080   * Returns a {@link NavigableSet} view of the distinct elements in this multiset.
081   * 
082   * @since 14.0 (present with return type {@code SortedSet} since 11.0)
083   */
084  @Override NavigableSet<E> elementSet();
085
086  /**
087   * {@inheritDoc}
088   *
089   * <p>The iterator returns the elements in ascending order according to this
090   * multiset's comparator.
091   */
092  @Override Iterator<E> iterator();
093
094  /**
095   * Returns a descending view of this multiset. Modifications made to either
096   * map will be reflected in the other.
097   */
098  SortedMultiset<E> descendingMultiset();
099
100  /**
101   * Returns a view of this multiset restricted to the elements less than
102   * {@code upperBound}, optionally including {@code upperBound} itself. The
103   * returned multiset is a view of this multiset, so changes to one will be
104   * reflected in the other. The returned multiset supports all operations that
105   * this multiset supports.
106   * 
107   * <p>The returned multiset will throw an {@link IllegalArgumentException} on
108   * attempts to add elements outside its range.
109   */
110  SortedMultiset<E> headMultiset(E upperBound, BoundType boundType);
111
112  /**
113   * Returns a view of this multiset restricted to the range between
114   * {@code lowerBound} and {@code upperBound}. The returned multiset is a view
115   * of this multiset, so changes to one will be reflected in the other. The
116   * returned multiset supports all operations that this multiset supports.
117   * 
118   * <p>The returned multiset will throw an {@link IllegalArgumentException} on
119   * attempts to add elements outside its range.
120   * 
121   * <p>This method is equivalent to
122   * {@code tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound,
123   * upperBoundType)}.
124   */
125  SortedMultiset<E> subMultiset(E lowerBound, BoundType lowerBoundType,
126      E upperBound, BoundType upperBoundType);
127
128  /**
129   * Returns a view of this multiset restricted to the elements greater than
130   * {@code lowerBound}, optionally including {@code lowerBound} itself. The
131   * returned multiset is a view of this multiset, so changes to one will be
132   * reflected in the other. The returned multiset supports all operations that
133   * this multiset supports.
134   * 
135   * <p>The returned multiset will throw an {@link IllegalArgumentException} on
136   * attempts to add elements outside its range.
137   */
138  SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);
139}