1/*
2 * Copyright (C) 2007 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.collect;
18
19import com.google.common.annotations.GwtCompatible;
20import static com.google.common.base.Preconditions.checkNotNull;
21
22import java.io.IOException;
23import java.io.ObjectInputStream;
24import java.io.ObjectOutputStream;
25import java.util.Collection;
26import java.util.Comparator;
27import java.util.Set;
28import java.util.SortedMap;
29import java.util.SortedSet;
30import java.util.TreeMap;
31import java.util.TreeSet;
32
33import javax.annotation.Nullable;
34
35/**
36 * Implementation of {@code Multimap} whose keys and values are ordered by
37 * their natural ordering or by supplied comparators. In all cases, this
38 * implementation uses {@link Comparable#compareTo} or {@link
39 * Comparator#compare} instead of {@link Object#equals} to determine
40 * equivalence of instances.
41 *
42 * <p><b>Warning:</b> The comparators or comparables used must be <i>consistent
43 * with equals</i> as explained by the {@link Comparable} class specification.
44 * Otherwise, the resulting multiset will violate the general contract of {@link
45 * SetMultimap}, which it is specified in terms of {@link Object#equals}.
46 *
47 * <p>The collections returned by {@code keySet} and {@code asMap} iterate
48 * through the keys according to the key comparator ordering or the natural
49 * ordering of the keys. Similarly, {@code get}, {@code removeAll}, and {@code
50 * replaceValues} return collections that iterate through the values according
51 * to the value comparator ordering or the natural ordering of the values. The
52 * collections generated by {@code entries}, {@code keys}, and {@code values}
53 * iterate across the keys according to the above key ordering, and for each
54 * key they iterate across the values according to the value ordering.
55 *
56 * <p>The multimap does not store duplicate key-value pairs. Adding a new
57 * key-value pair equal to an existing key-value pair has no effect.
58 *
59 * <p>Depending on the comparators, null keys and values may or may not be
60 * supported. The natural ordering does not support nulls. All optional multimap
61 * methods are supported, and all returned views are modifiable.
62 *
63 * <p>This class is not threadsafe when any concurrent operations update the
64 * multimap. Concurrent read operations will work correctly. To allow concurrent
65 * update operations, wrap your multimap with a call to {@link
66 * Multimaps#synchronizedSortedSetMultimap}.
67 *
68 * @author Jared Levy
69 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
70 */
71@GwtCompatible(serializable = true)
72public class TreeMultimap<K, V> extends AbstractSortedSetMultimap<K, V> {
73  private transient Comparator<? super K> keyComparator;
74  private transient Comparator<? super V> valueComparator;
75
76  /**
77   * Creates an empty {@code TreeMultimap} ordered by the natural ordering of
78   * its keys and values.
79   */
80  @SuppressWarnings("unchecked") // eclipse doesn't like the raw Comparable
81  public static <K extends Comparable, V extends Comparable>
82      TreeMultimap<K, V> create() {
83    return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural());
84  }
85
86  /**
87   * Creates an empty {@code TreeMultimap} instance using explicit comparators.
88   * Neither comparator may be null; use {@link Ordering#natural()} to specify
89   * natural order.
90   *
91   * @param keyComparator the comparator that determines the key ordering
92   * @param valueComparator the comparator that determines the value ordering
93   */
94  public static <K, V> TreeMultimap<K, V> create(
95      Comparator<? super K> keyComparator,
96      Comparator<? super V> valueComparator) {
97    return new TreeMultimap<K, V>(checkNotNull(keyComparator),
98        checkNotNull(valueComparator));
99  }
100
101  /**
102   * Constructs a {@code TreeMultimap}, ordered by the natural ordering of its
103   * keys and values, with the same mappings as the specified multimap.
104   *
105   * @param multimap the multimap whose contents are copied to this multimap
106   */
107  @SuppressWarnings("unchecked") // eclipse doesn't like the raw Comparable
108  public static <K extends Comparable, V extends Comparable>
109      TreeMultimap<K, V> create(Multimap<? extends K, ? extends V> multimap) {
110    return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural(),
111        multimap);
112  }
113
114  // Used by the TreeMultimap serialization test.
115  TreeMultimap() {
116    this(null, null);
117  }
118
119  // Must be package-private so multimaps with null comparators can be
120  // serialized (which can be created with Multimaps.newTreeMultimap()). Once
121  // that method is removed, this constructor can be made private.
122  TreeMultimap(@Nullable Comparator<? super K> keyComparator,
123      @Nullable Comparator<? super V> valueComparator) {
124    super((keyComparator == null)
125        ? new TreeMap<K, Collection<V>>()
126        : new TreeMap<K, Collection<V>>(keyComparator));
127    this.keyComparator = keyComparator;
128    this.valueComparator = valueComparator;
129  }
130
131  private TreeMultimap(Comparator<? super K> keyComparator,
132      Comparator<? super V> valueComparator,
133      Multimap<? extends K, ? extends V> multimap) {
134    this(keyComparator, valueComparator);
135    putAll(multimap);
136  }
137
138  /**
139   * {@inheritDoc}
140   *
141   * <p>Creates an empty {@code TreeSet} for a collection of values for one key.
142   *
143   * @return a new {@code TreeSet} containing a collection of values for one
144   *     key
145   */
146  @Override SortedSet<V> createCollection() {
147    return (valueComparator == null)
148        ? new TreeSet<V>() : new TreeSet<V>(valueComparator);
149  }
150
151  /**
152   * Returns the comparator that orders the multimap keys.
153   */
154  public Comparator<? super K> keyComparator() {
155    return keyComparator;
156  }
157
158  public Comparator<? super V> valueComparator() {
159    return valueComparator;
160  }
161
162  /**
163   * {@inheritDoc}
164   *
165   * <p>Because a {@code TreeMultimap} has unique sorted keys, this method
166   * returns a {@link SortedSet}, instead of the {@link Set} specified in the
167   * {@link Multimap} interface.
168   */
169  @Override public SortedSet<K> keySet() {
170    return (SortedSet<K>) super.keySet();
171  }
172
173  /**
174   * {@inheritDoc}
175   *
176   * <p>Because a {@code TreeMultimap} has unique sorted keys, this method
177   * returns a {@link SortedMap}, instead of the {@link java.util.Map} specified
178   * in the {@link Multimap} interface.
179   */
180  @Override public SortedMap<K, Collection<V>> asMap() {
181    return (SortedMap<K, Collection<V>>) super.asMap();
182  }
183
184  /**
185   * @serialData key comparator, value comparator, number of distinct keys, and
186   *     then for each distinct key: the key, number of values for that key, and
187   *     key values
188   */
189  private void writeObject(ObjectOutputStream stream) throws IOException {
190    stream.defaultWriteObject();
191    stream.writeObject(keyComparator());
192    stream.writeObject(valueComparator());
193    Serialization.writeMultimap(this, stream);
194  }
195
196  @SuppressWarnings("unchecked") // reading data stored by writeObject
197  private void readObject(ObjectInputStream stream)
198      throws IOException, ClassNotFoundException {
199    stream.defaultReadObject();
200    keyComparator = (Comparator<? super K>) stream.readObject();
201    valueComparator = (Comparator<? super V>) stream.readObject();
202    setMap(new TreeMap<K, Collection<V>>(keyComparator));
203    Serialization.populateMultimap(this, stream);
204  }
205
206  private static final long serialVersionUID = 0;
207}
208