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.Map;
22 import java.util.Set;
23
24 import javax.annotation.Nullable;
25
26 /**
27 * A bimap (or "bidirectional map") is a map that preserves the uniqueness of
28 * its values as well as that of its keys. This constraint enables bimaps to
29 * support an "inverse view", which is another bimap containing the same entries
30 * as this bimap but with reversed keys and values.
31 *
32 * <p>See the Guava User Guide article on <a href=
33 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#BiMap">
34 * {@code BiMap}</a>.
35 *
36 * @author Kevin Bourrillion
37 * @since 2.0 (imported from Google Collections Library)
38 */
39 @GwtCompatible
40 public interface BiMap<K, V> extends Map<K, V> {
41 // Modification Operations
42
43 /**
44 * {@inheritDoc}
45 *
46 * @throws IllegalArgumentException if the given value is already bound to a
47 * different key in this bimap. The bimap will remain unmodified in this
48 * event. To avoid this exception, call {@link #forcePut} instead.
49 */
50 @Override
51 V put(@Nullable K key, @Nullable V value);
52
53 /**
54 * An alternate form of {@code put} that silently removes any existing entry
55 * with the value {@code value} before proceeding with the {@link #put}
56 * operation. If the bimap previously contained the provided key-value
57 * mapping, this method has no effect.
58 *
59 * <p>Note that a successful call to this method could cause the size of the
60 * bimap to increase by one, stay the same, or even decrease by one.
61 *
62 * <p><b>Warning:</b> If an existing entry with this value is removed, the key
63 * for that entry is discarded and not returned.
64 *
65 * @param key the key with which the specified value is to be associated
66 * @param value the value to be associated with the specified key
67 * @return the value which was previously associated with the key, which may
68 * be {@code null}, or {@code null} if there was no previous entry
69 */
70 V forcePut(@Nullable K key, @Nullable V value);
71
72 // Bulk Operations
73
74 /**
75 * {@inheritDoc}
76 *
77 * <p><b>Warning:</b> the results of calling this method may vary depending on
78 * the iteration order of {@code map}.
79 *
80 * @throws IllegalArgumentException if an attempt to {@code put} any
81 * entry fails. Note that some map entries may have been added to the
82 * bimap before the exception was thrown.
83 */
84 @Override
85 void putAll(Map<? extends K, ? extends V> map);
86
87 // Views
88
89 /**
90 * {@inheritDoc}
91 *
92 * <p>Because a bimap has unique values, this method returns a {@link Set},
93 * instead of the {@link java.util.Collection} specified in the {@link Map}
94 * interface.
95 */
96 @Override
97 Set<V> values();
98
99 /**
100 * Returns the inverse view of this bimap, which maps each of this bimap's
101 * values to its associated key. The two bimaps are backed by the same data;
102 * any changes to one will appear in the other.
103 *
104 * <p><b>Note:</b>There is no guaranteed correspondence between the iteration
105 * order of a bimap and that of its inverse.
106 *
107 * @return the inverse view of this bimap
108 */
109 BiMap<V, K> inverse();
110 }