001 /*
002 * Copyright (C) 2007 Google Inc.
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 (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 V put(@Nullable K key, @Nullable V value);
047
048 /**
049 * An alternate form of {@code put} that silently removes any existing entry
050 * with the value {@code value} before proceeding with the {@link #put}
051 * operation. If the bimap previously contained the provided key-value
052 * mapping, this method has no effect.
053 *
054 * <p>Note that a successful call to this method could cause the size of the
055 * bimap to increase by one, stay the same, or even decrease by one.
056 *
057 * <p><b>Warning</b>: If an existing entry with this value is removed, the key
058 * for that entry is discarded and not returned.
059 *
060 * @param key the key with which the specified value is to be associated
061 * @param value the value to be associated with the specified key
062 * @return the value which was previously associated with the key, which may
063 * be {@code null}, or {@code null} if there was no previous entry
064 */
065 V forcePut(@Nullable K key, @Nullable V value);
066
067 // Bulk Operations
068
069 /**
070 * {@inheritDoc}
071 *
072 * <p><b>Warning:</b> the results of calling this method may vary depending on
073 * the iteration order of {@code map}.
074 *
075 * @throws IllegalArgumentException if an attempt to {@code put} any
076 * entry fails. Note that some map entries may have been added to the
077 * bimap before the exception was thrown.
078 */
079 void putAll(Map<? extends K, ? extends V> map);
080
081 // Views
082
083 /**
084 * {@inheritDoc}
085 *
086 * <p>Because a bimap has unique values, this method returns a {@link Set},
087 * instead of the {@link java.util.Collection} specified in the {@link Map}
088 * interface.
089 */
090 Set<V> values();
091
092 /**
093 * Returns the inverse view of this bimap, which maps each of this bimap's
094 * values to its associated key. The two bimaps are backed by the same data;
095 * any changes to one will appear in the other.
096 *
097 * <p><b>Note:</b>There is no guaranteed correspondence between the iteration
098 * order of a bimap and that of its inverse.
099 *
100 * @return the inverse view of this bimap
101 */
102 BiMap<V, K> inverse();
103 }