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
017 package com.google.common.collect;
018
019 import com.google.common.annotations.Beta;
020 import com.google.common.annotations.GwtCompatible;
021
022 import java.util.Collection;
023 import java.util.Comparator;
024 import java.util.Iterator;
025 import java.util.SortedSet;
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
048 public interface SortedMultiset<E> extends Multiset<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 SortedSet} view of the distinct elements in this multiset.
081 */
082 @Override SortedSet<E> elementSet();
083
084 /**
085 * {@inheritDoc}
086 *
087 * <p>The iterator returns the elements in ascending order according to this
088 * multiset's comparator.
089 */
090 @Override Iterator<E> iterator();
091
092 /**
093 * Returns a descending view of this multiset. Modifications made to either
094 * map will be reflected in the other.
095 */
096 SortedMultiset<E> descendingMultiset();
097
098 /**
099 * Returns a view of this multiset restricted to the elements less than
100 * {@code upperBound}, optionally including {@code upperBound} itself. The
101 * returned multiset is a view of this multiset, so changes to one will be
102 * reflected in the other. The returned multiset supports all operations that
103 * this multiset supports.
104 *
105 * <p>The returned multiset will throw an {@link IllegalArgumentException} on
106 * attempts to add elements outside its range.
107 */
108 SortedMultiset<E> headMultiset(E upperBound, BoundType boundType);
109
110 /**
111 * Returns a view of this multiset restricted to the range between
112 * {@code lowerBound} and {@code upperBound}. The returned multiset is a view
113 * of this multiset, so changes to one will be reflected in the other. The
114 * returned multiset supports all operations that this multiset supports.
115 *
116 * <p>The returned multiset will throw an {@link IllegalArgumentException} on
117 * attempts to add elements outside its range.
118 *
119 * <p>This method is equivalent to
120 * {@code tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound,
121 * upperBoundType)}.
122 */
123 SortedMultiset<E> subMultiset(E lowerBound, BoundType lowerBoundType,
124 E upperBound, BoundType upperBoundType);
125
126 /**
127 * Returns a view of this multiset restricted to the elements greater than
128 * {@code lowerBound}, optionally including {@code lowerBound} itself. The
129 * returned multiset is a view of this multiset, so changes to one will be
130 * reflected in the other. The returned multiset supports all operations that
131 * this multiset supports.
132 *
133 * <p>The returned multiset will throw an {@link IllegalArgumentException} on
134 * attempts to add elements outside its range.
135 */
136 SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);
137 }