001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of 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,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect;
018
019import static com.google.common.base.Preconditions.checkNotNull;
020
021import com.google.common.annotations.GwtCompatible;
022import com.google.common.annotations.GwtIncompatible;
023
024import java.io.IOException;
025import java.io.ObjectInputStream;
026import java.io.ObjectOutputStream;
027import java.util.Collection;
028import java.util.Comparator;
029import java.util.SortedMap;
030import java.util.SortedSet;
031import java.util.TreeMap;
032import java.util.TreeSet;
033
034/**
035 * Implementation of {@code Multimap} whose keys and values are ordered by
036 * their natural ordering or by supplied comparators. In all cases, this
037 * implementation uses {@link Comparable#compareTo} or {@link
038 * Comparator#compare} instead of {@link Object#equals} to determine
039 * equivalence of instances.
040 *
041 * <p><b>Warning:</b> The comparators or comparables used must be <i>consistent
042 * with equals</i> as explained by the {@link Comparable} class specification.
043 * Otherwise, the resulting multiset will violate the general contract of {@link
044 * SetMultimap}, which it is specified in terms of {@link Object#equals}.
045 *
046 * <p>The collections returned by {@code keySet} and {@code asMap} iterate
047 * through the keys according to the key comparator ordering or the natural
048 * ordering of the keys. Similarly, {@code get}, {@code removeAll}, and {@code
049 * replaceValues} return collections that iterate through the values according
050 * to the value comparator ordering or the natural ordering of the values. The
051 * collections generated by {@code entries}, {@code keys}, and {@code values}
052 * iterate across the keys according to the above key ordering, and for each
053 * key they iterate across the values according to the value ordering.
054 *
055 * <p>The multimap does not store duplicate key-value pairs. Adding a new
056 * key-value pair equal to an existing key-value pair has no effect.
057 *
058 * <p>Null keys and values are permitted (provided, of course, that the
059 * respective comparators support them). All optional multimap methods are
060 * supported, and all returned views are modifiable.
061 *
062 * <p>This class is not threadsafe when any concurrent operations update the
063 * multimap. Concurrent read operations will work correctly. To allow concurrent
064 * update operations, wrap your multimap with a call to {@link
065 * Multimaps#synchronizedSortedSetMultimap}.
066 * 
067 * <p>See the Guava User Guide article on <a href=
068 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multimap">
069 * {@code Multimap}</a>.
070 *
071 * @author Jared Levy
072 * @since 2.0 (imported from Google Collections Library)
073 */
074@GwtCompatible(serializable = true, emulated = true)
075public class TreeMultimap<K, V> extends AbstractSortedSetMultimap<K, V> {
076  private transient Comparator<? super K> keyComparator;
077  private transient Comparator<? super V> valueComparator;
078
079  /**
080   * Creates an empty {@code TreeMultimap} ordered by the natural ordering of
081   * its keys and values.
082   */
083  public static <K extends Comparable, V extends Comparable>
084      TreeMultimap<K, V> create() {
085    return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural());
086  }
087
088  /**
089   * Creates an empty {@code TreeMultimap} instance using explicit comparators.
090   * Neither comparator may be null; use {@link Ordering#natural()} to specify
091   * natural order.
092   *
093   * @param keyComparator the comparator that determines the key ordering
094   * @param valueComparator the comparator that determines the value ordering
095   */
096  public static <K, V> TreeMultimap<K, V> create(
097      Comparator<? super K> keyComparator,
098      Comparator<? super V> valueComparator) {
099    return new TreeMultimap<K, V>(checkNotNull(keyComparator),
100        checkNotNull(valueComparator));
101  }
102
103  /**
104   * Constructs a {@code TreeMultimap}, ordered by the natural ordering of its
105   * keys and values, with the same mappings as the specified multimap.
106   *
107   * @param multimap the multimap whose contents are copied to this multimap
108   */
109  public static <K extends Comparable, V extends Comparable>
110      TreeMultimap<K, V> create(Multimap<? extends K, ? extends V> multimap) {
111    return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural(),
112        multimap);
113  }
114
115  TreeMultimap(Comparator<? super K> keyComparator,
116      Comparator<? super V> valueComparator) {
117    super(new TreeMap<K, Collection<V>>(keyComparator));
118    this.keyComparator = keyComparator;
119    this.valueComparator = valueComparator;
120  }
121
122  private TreeMultimap(Comparator<? super K> keyComparator,
123      Comparator<? super V> valueComparator,
124      Multimap<? extends K, ? extends V> multimap) {
125    this(keyComparator, valueComparator);
126    putAll(multimap);
127  }
128
129  /**
130   * {@inheritDoc}
131   *
132   * <p>Creates an empty {@code TreeSet} for a collection of values for one key.
133   *
134   * @return a new {@code TreeSet} containing a collection of values for one
135   *     key
136   */
137  @Override SortedSet<V> createCollection() {
138    return new TreeSet<V>(valueComparator);
139  }
140
141  /**
142   * Returns the comparator that orders the multimap keys.
143   */
144  public Comparator<? super K> keyComparator() {
145    return keyComparator;
146  }
147
148  @Override
149  public Comparator<? super V> valueComparator() {
150    return valueComparator;
151  }
152
153  /**
154   * {@inheritDoc}
155   *
156   * <p>Because a {@code TreeMultimap} has unique sorted keys, this method
157   * returns a {@link SortedSet}, instead of the {@link java.util.Set} specified
158   * in the {@link Multimap} interface.
159   */
160  @Override public SortedSet<K> keySet() {
161    return (SortedSet<K>) super.keySet();
162  }
163
164  /**
165   * {@inheritDoc}
166   *
167   * <p>Because a {@code TreeMultimap} has unique sorted keys, this method
168   * returns a {@link SortedMap}, instead of the {@link java.util.Map} specified
169   * in the {@link Multimap} interface.
170   */
171  @Override public SortedMap<K, Collection<V>> asMap() {
172    return (SortedMap<K, Collection<V>>) super.asMap();
173  }
174
175  /**
176   * @serialData key comparator, value comparator, number of distinct keys, and
177   *     then for each distinct key: the key, number of values for that key, and
178   *     key values
179   */
180  @GwtIncompatible("java.io.ObjectOutputStream")
181  private void writeObject(ObjectOutputStream stream) throws IOException {
182    stream.defaultWriteObject();
183    stream.writeObject(keyComparator());
184    stream.writeObject(valueComparator());
185    Serialization.writeMultimap(this, stream);
186  }
187
188  @GwtIncompatible("java.io.ObjectInputStream")
189  @SuppressWarnings("unchecked") // reading data stored by writeObject
190  private void readObject(ObjectInputStream stream)
191      throws IOException, ClassNotFoundException {
192    stream.defaultReadObject();
193    keyComparator = checkNotNull((Comparator<? super K>) stream.readObject());
194    valueComparator = checkNotNull((Comparator<? super V>) stream.readObject());
195    setMap(new TreeMap<K, Collection<V>>(keyComparator));
196    Serialization.populateMultimap(this, stream);
197  }
198
199  @GwtIncompatible("not needed in emulated source")
200  private static final long serialVersionUID = 0;
201}