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 either their
028 * natural order or an explicit {@link Comparator}. This order is reflected when iterating over the
029 * sorted multiset, either directly, or through its {@code elementSet} or {@code entrySet} views. In
030 * all cases, this implementation uses {@link Comparable#compareTo} or {@link Comparator#compare}
031 * instead of {@link Object#equals} to determine equivalence of instances.
032 *
033 * <p><b>Warning:</b> The comparison must be <i>consistent with equals</i> as explained by the
034 * {@link Comparable} class specification. Otherwise, the resulting multiset will violate the {@link
035 * Collection} contract, which it is specified in terms of {@link Object#equals}.
036 *
037 * <p>See the Guava User Guide article on <a href=
038 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset"> {@code
039 * Multiset}</a>.
040 *
041 * @author Louis Wasserman
042 * @since 11.0
043 */
044@GwtCompatible(emulated = true)
045public interface SortedMultiset<E> extends SortedMultisetBridge<E>, SortedIterable<E> {
046  /**
047   * Returns the comparator that orders this multiset, or {@link Ordering#natural()} if the natural
048   * ordering of the elements is used.
049   */
050  Comparator<? super E> comparator();
051
052  /**
053   * Returns the entry of the first element in this multiset, or {@code null} if this multiset is
054   * empty.
055   */
056  Entry<E> firstEntry();
057
058  /**
059   * Returns the entry of the last element in this multiset, or {@code null} if this multiset is
060   * empty.
061   */
062  Entry<E> lastEntry();
063
064  /**
065   * Returns and removes the entry associated with the lowest element in this multiset, or returns
066   * {@code null} if this multiset is empty.
067   */
068  Entry<E> pollFirstEntry();
069
070  /**
071   * Returns and removes the entry associated with the greatest element in this multiset, or returns
072   * {@code null} if this multiset is empty.
073   */
074  Entry<E> pollLastEntry();
075
076  /**
077   * Returns a {@link NavigableSet} view of the distinct elements in this multiset.
078   *
079   * @since 14.0 (present with return type {@code SortedSet} since 11.0)
080   */
081  @Override
082  NavigableSet<E> elementSet();
083
084  /**
085   * {@inheritDoc}
086   *
087   * <p>The {@code entrySet}'s iterator returns entries in ascending element order according to the
088   * this multiset's comparator.
089   */
090  @Override
091  Set<Entry<E>> entrySet();
092
093  /**
094   * {@inheritDoc}
095   *
096   * <p>The iterator returns the elements in ascending order according to this multiset's
097   * comparator.
098   */
099  @Override
100  Iterator<E> iterator();
101
102  /**
103   * Returns a descending view of this multiset. Modifications made to either map will be reflected
104   * in the other.
105   */
106  SortedMultiset<E> descendingMultiset();
107
108  /**
109   * Returns a view of this multiset restricted to the elements less than {@code upperBound},
110   * optionally including {@code upperBound} itself. The returned multiset is a view of this
111   * multiset, so changes to one will be reflected in the other. The returned multiset supports all
112   * operations that this multiset supports.
113   *
114   * <p>The returned multiset will throw an {@link IllegalArgumentException} on attempts to add
115   * elements outside its range.
116   */
117  SortedMultiset<E> headMultiset(E upperBound, BoundType boundType);
118
119  /**
120   * Returns a view of this multiset restricted to the range between {@code lowerBound} and {@code
121   * upperBound}. The returned multiset is a view of this multiset, so changes to one will be
122   * reflected in the other. The returned multiset supports all operations that this multiset
123   * supports.
124   *
125   * <p>The returned multiset will throw an {@link IllegalArgumentException} on attempts to add
126   * elements outside its range.
127   *
128   * <p>This method is equivalent to {@code tailMultiset(lowerBound,
129   * lowerBoundType).headMultiset(upperBound, upperBoundType)}.
130   */
131  SortedMultiset<E> subMultiset(
132      E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType);
133
134  /**
135   * Returns a view of this multiset restricted to the elements greater than {@code lowerBound},
136   * optionally including {@code lowerBound} itself. The returned multiset is a view of this
137   * multiset, so changes to one will be reflected in the other. The returned multiset supports all
138   * operations that this multiset supports.
139   *
140   * <p>The returned multiset will throw an {@link IllegalArgumentException} on attempts to add
141   * elements outside its range.
142   */
143  SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType);
144}