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.GwtCompatible;
020import java.util.Collection;
021import java.util.Comparator;
022import java.util.Iterator;
023import java.util.NavigableSet;
024import java.util.Set;
025
026/**
027 * A {@link Multiset} which maintains the ordering of its elements, according to
028 * either their natural order or an explicit {@link Comparator}. This order is
029 * reflected when iterating over the sorted multiset, either directly, or through
030 * its {@code elementSet} or {@code entrySet} views.  In all cases,
031 * this implementation uses {@link Comparable#compareTo} or
032 * {@link Comparator#compare} instead of {@link Object#equals} to determine
033 * equivalence of instances.
034 *
035 * <p><b>Warning:</b> The comparison must be <i>consistent with equals</i> as
036 * explained by the {@link Comparable} class specification. Otherwise, the
037 * resulting multiset will violate the {@link Collection} contract, which it is
038 * specified in terms of {@link Object#equals}.
039 *
040 * <p>See the Guava User Guide article on <a href=
041 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset">
042 * {@code Multiset}</a>.
043 *
044 * @author Louis Wasserman
045 * @since 11.0
046 */
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
085  NavigableSet<E> elementSet();
086
087  /**
088   * {@inheritDoc}
089   *
090   * <p>The {@code entrySet}'s iterator returns entries in ascending element
091   * order according to the this multiset's comparator.
092   */
093  @Override
094  Set<Entry<E>> entrySet();
095
096  /**
097   * {@inheritDoc}
098   *
099   * <p>The iterator returns the elements in ascending order according to this
100   * multiset's comparator.
101   */
102  @Override
103  Iterator<E> iterator();
104
105  /**
106   * Returns a descending view of this multiset. Modifications made to either
107   * map will be reflected in the other.
108   */
109  SortedMultiset<E> descendingMultiset();
110
111  /**
112   * Returns a view of this multiset restricted to the elements less than
113   * {@code upperBound}, optionally including {@code upperBound} itself. The
114   * returned multiset is a view of this multiset, so changes to one will be
115   * reflected in the other. The returned multiset supports all operations that
116   * 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  SortedMultiset<E> headMultiset(E upperBound, BoundType boundType);
122
123  /**
124   * Returns a view of this multiset restricted to the range between
125   * {@code lowerBound} and {@code upperBound}. The returned multiset is a view
126   * of this multiset, so changes to one will be reflected in the other. The
127   * returned multiset supports all operations that this multiset supports.
128   *
129   * <p>The returned multiset will throw an {@link IllegalArgumentException} on
130   * attempts to add elements outside its range.
131   *
132   * <p>This method is equivalent to
133   * {@code tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound,
134   * upperBoundType)}.
135   */
136  SortedMultiset<E> subMultiset(
137      E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType);
138
139  /**
140   * Returns a view of this multiset restricted to the elements greater than
141   * {@code lowerBound}, optionally including {@code lowerBound} itself. The
142   * returned multiset is a view of this multiset, so changes to one will be
143   * reflected in the other. The returned multiset supports all operations that
144   * this multiset supports.
145   *
146   * <p>The returned multiset will throw an {@link IllegalArgumentException} on
147   * attempts to add elements outside its range.
148   */
149  SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);
150}