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
017 package com.google.common.collect;
018
019 import com.google.common.annotations.GwtCompatible;
020
021 import java.util.Map;
022 import java.util.Set;
023
024 import javax.annotation.Nullable;
025
026 /**
027 * A bimap (or "bidirectional map") is a map that preserves the uniqueness of
028 * its values as well as that of its keys. This constraint enables bimaps to
029 * support an "inverse view", which is another bimap containing the same entries
030 * as this bimap but with reversed keys and values.
031 *
032 * <p>See the Guava User Guide article on <a href=
033 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#BiMap">
034 * {@code BiMap}</a>.
035 *
036 * @author Kevin Bourrillion
037 * @since 2.0 (imported from Google Collections Library)
038 */
039 @GwtCompatible
040 public interface BiMap<K, V> extends Map<K, V> {
041 // Modification Operations
042
043 /**
044 * {@inheritDoc}
045 *
046 * @throws IllegalArgumentException if the given value is already bound to a
047 * different key in this bimap. The bimap will remain unmodified in this
048 * event. To avoid this exception, call {@link #forcePut} instead.
049 */
050 @Override
051 V put(@Nullable K key, @Nullable V value);
052
053 /**
054 * An alternate form of {@code put} that silently removes any existing entry
055 * with the value {@code value} before proceeding with the {@link #put}
056 * operation. If the bimap previously contained the provided key-value
057 * mapping, this method has no effect.
058 *
059 * <p>Note that a successful call to this method could cause the size of the
060 * bimap to increase by one, stay the same, or even decrease by one.
061 *
062 * <p><b>Warning:</b> If an existing entry with this value is removed, the key
063 * for that entry is discarded and not returned.
064 *
065 * @param key the key with which the specified value is to be associated
066 * @param value the value to be associated with the specified key
067 * @return the value which was previously associated with the key, which may
068 * be {@code null}, or {@code null} if there was no previous entry
069 */
070 V forcePut(@Nullable K key, @Nullable V value);
071
072 // Bulk Operations
073
074 /**
075 * {@inheritDoc}
076 *
077 * <p><b>Warning:</b> the results of calling this method may vary depending on
078 * the iteration order of {@code map}.
079 *
080 * @throws IllegalArgumentException if an attempt to {@code put} any
081 * entry fails. Note that some map entries may have been added to the
082 * bimap before the exception was thrown.
083 */
084 @Override
085 void putAll(Map<? extends K, ? extends V> map);
086
087 // Views
088
089 /**
090 * {@inheritDoc}
091 *
092 * <p>Because a bimap has unique values, this method returns a {@link Set},
093 * instead of the {@link java.util.Collection} specified in the {@link Map}
094 * interface.
095 */
096 @Override
097 Set<V> values();
098
099 /**
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 }