1   /*
2    * Copyright (C) 2007 The Guava Authors
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  
17  package com.google.common.collect;
18  
19  import com.google.common.annotations.GwtCompatible;
20  
21  import java.util.Collection;
22  import java.util.Map;
23  import java.util.Set;
24  
25  import javax.annotation.Nullable;
26  
27  /**
28   * Basic implementation of the {@link SetMultimap} interface. It's a wrapper
29   * around {@link AbstractMapBasedMultimap} that converts the returned collections into
30   * {@code Sets}. The {@link #createCollection} method must return a {@code Set}.
31   *
32   * @author Jared Levy
33   */
34  @GwtCompatible
35  abstract class AbstractSetMultimap<K, V>
36      extends AbstractMapBasedMultimap<K, V> implements SetMultimap<K, V> {
37    /**
38     * Creates a new multimap that uses the provided map.
39     *
40     * @param map place to store the mapping from each key to its corresponding
41     *     values
42     */
43    protected AbstractSetMultimap(Map<K, Collection<V>> map) {
44      super(map);
45    }
46  
47    @Override abstract Set<V> createCollection();
48  
49    @Override Set<V> createUnmodifiableEmptyCollection() {
50      return ImmutableSet.of();
51    }
52  
53    // Following Javadoc copied from SetMultimap.
54  
55    /**
56     * {@inheritDoc}
57     *
58     * <p>Because a {@code SetMultimap} has unique values for a given key, this
59     * method returns a {@link Set}, instead of the {@link Collection} specified
60     * in the {@link Multimap} interface.
61     */
62    @Override public Set<V> get(@Nullable K key) {
63      return (Set<V>) super.get(key);
64    }
65  
66    /**
67     * {@inheritDoc}
68     *
69     * <p>Because a {@code SetMultimap} has unique values for a given key, this
70     * method returns a {@link Set}, instead of the {@link Collection} specified
71     * in the {@link Multimap} interface.
72     */
73    @Override public Set<Map.Entry<K, V>> entries() {
74      return (Set<Map.Entry<K, V>>) super.entries();
75    }
76  
77    /**
78     * {@inheritDoc}
79     *
80     * <p>Because a {@code SetMultimap} has unique values for a given key, this
81     * method returns a {@link Set}, instead of the {@link Collection} specified
82     * in the {@link Multimap} interface.
83     */
84    @Override public Set<V> removeAll(@Nullable Object key) {
85      return (Set<V>) super.removeAll(key);
86    }
87  
88    /**
89     * {@inheritDoc}
90     *
91     * <p>Because a {@code SetMultimap} has unique values for a given key, this
92     * method returns a {@link Set}, instead of the {@link Collection} specified
93     * in the {@link Multimap} interface.
94     *
95     * <p>Any duplicates in {@code values} will be stored in the multimap once.
96     */
97    @Override public Set<V> replaceValues(
98        @Nullable K key, Iterable<? extends V> values) {
99      return (Set<V>) super.replaceValues(key, values);
100   }
101 
102   /**
103    * {@inheritDoc}
104    *
105    * <p>Though the method signature doesn't say so explicitly, the returned map
106    * has {@link Set} values.
107    */
108   @Override public Map<K, Collection<V>> asMap() {
109     return super.asMap();
110   }
111 
112   /**
113    * Stores a key-value pair in the multimap.
114    *
115    * @param key key to store in the multimap
116    * @param value value to store in the multimap
117    * @return {@code true} if the method increased the size of the multimap, or
118    *     {@code false} if the multimap already contained the key-value pair
119    */
120   @Override public boolean put(@Nullable K key, @Nullable V value) {
121     return super.put(key, value);
122   }
123 
124   /**
125    * Compares the specified object to this multimap for equality.
126    *
127    * <p>Two {@code SetMultimap} instances are equal if, for each key, they
128    * contain the same values. Equality does not depend on the ordering of keys
129    * or values.
130    */
131   @Override public boolean equals(@Nullable Object object) {
132     return super.equals(object);
133   }
134 
135   private static final long serialVersionUID = 7431625294878419160L;
136 }