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 * @author Kevin Bourrillion
033 * @since 2.0 (imported from Google Collections Library)
034 */
035 @GwtCompatible
036 public interface BiMap<K, V> extends Map<K, V> {
037 // Modification Operations
038
039 /**
040 * {@inheritDoc}
041 *
042 * @throws IllegalArgumentException if the given value is already bound to a
043 * different key in this bimap. The bimap will remain unmodified in this
044 * event. To avoid this exception, call {@link #forcePut} instead.
045 */
046 @Override
047 V put(@Nullable K key, @Nullable V value);
048
049 /**
050 * An alternate form of {@code put} that silently removes any existing entry
051 * with the value {@code value} before proceeding with the {@link #put}
052 * operation. If the bimap previously contained the provided key-value
053 * mapping, this method has no effect.
054 *
055 * <p>Note that a successful call to this method could cause the size of the
056 * bimap to increase by one, stay the same, or even decrease by one.
057 *
058 * <p><b>Warning:</b> If an existing entry with this value is removed, the key
059 * for that entry is discarded and not returned.
060 *
061 * @param key the key with which the specified value is to be associated
062 * @param value the value to be associated with the specified key
063 * @return the value which was previously associated with the key, which may
064 * be {@code null}, or {@code null} if there was no previous entry
065 */
066 V forcePut(@Nullable K key, @Nullable V value);
067
068 // Bulk Operations
069
070 /**
071 * {@inheritDoc}
072 *
073 * <p><b>Warning:</b> the results of calling this method may vary depending on
074 * the iteration order of {@code map}.
075 *
076 * @throws IllegalArgumentException if an attempt to {@code put} any
077 * entry fails. Note that some map entries may have been added to the
078 * bimap before the exception was thrown.
079 */
080 @Override
081 void putAll(Map<? extends K, ? extends V> map);
082
083 // Views
084
085 /**
086 * {@inheritDoc}
087 *
088 * <p>Because a bimap has unique values, this method returns a {@link Set},
089 * instead of the {@link java.util.Collection} specified in the {@link Map}
090 * interface.
091 */
092 @Override
093 Set<V> values();
094
095 /**
096 * Returns the inverse view of this bimap, which maps each of this bimap's
097 * values to its associated key. The two bimaps are backed by the same data;
098 * any changes to one will appear in the other.
099 *
100 * <p><b>Note:</b>There is no guaranteed correspondence between the iteration
101 * order of a bimap and that of its inverse.
102 *
103 * @return the inverse view of this bimap
104 */
105 BiMap<V, K> inverse();
106 }