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
017package com.google.common.collect;
018
019import com.google.common.annotations.GwtCompatible;
020import com.google.errorprone.annotations.CanIgnoreReturnValue;
021import java.util.Map;
022import java.util.Set;
023import javax.annotation.CheckForNull;
024import org.checkerframework.checker.nullness.qual.Nullable;
025
026/**
027 * A bimap (or "bidirectional map") is a map that preserves the uniqueness of its values as well as
028 * that of its keys. This constraint enables bimaps to support an "inverse view", which is another
029 * bimap containing the same entries as this bimap but with reversed keys and values.
030 *
031 * <h3>Implementations</h3>
032 *
033 * <ul>
034 *   <li>{@link ImmutableBiMap}
035 *   <li>{@link HashBiMap}
036 *   <li>{@link EnumBiMap}
037 *   <li>{@link EnumHashBiMap}
038 * </ul>
039 *
040 * <p>See the Guava User Guide article on <a href=
041 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">{@code BiMap}</a>.
042 *
043 * @author Kevin Bourrillion
044 * @since 2.0
045 */
046@GwtCompatible
047public interface BiMap<K extends @Nullable Object, V extends @Nullable Object> extends Map<K, V> {
048  // Modification Operations
049
050  /**
051   * {@inheritDoc}
052   *
053   * @throws IllegalArgumentException if the given value is already bound to a different key in this
054   *     bimap. The bimap will remain unmodified in this event. To avoid this exception, call {@link
055   *     #forcePut} instead.
056   */
057  @CanIgnoreReturnValue
058  @Override
059  @CheckForNull
060  V put(@ParametricNullness K key, @ParametricNullness V value);
061
062  /**
063   * An alternate form of {@code put} that silently removes any existing entry with the value {@code
064   * value} before proceeding with the {@link #put} operation. If the bimap previously contained the
065   * provided key-value mapping, this method has no effect.
066   *
067   * <p>Note that a successful call to this method could cause the size of the bimap to increase by
068   * one, stay the same, or even decrease by one.
069   *
070   * <p><b>Warning:</b> If an existing entry with this value is removed, the key for that entry is
071   * discarded and not returned.
072   *
073   * @param key the key with which the specified value is to be associated
074   * @param value the value to be associated with the specified key
075   * @return the value that was previously associated with the key, or {@code null} if there was no
076   *     previous entry. (If the bimap contains null values, then {@code forcePut}, like {@code
077   *     put}, returns {@code null} both if the key is absent and if it is present with a null
078   *     value.)
079   */
080  @CanIgnoreReturnValue
081  @CheckForNull
082  V forcePut(@ParametricNullness K key, @ParametricNullness V value);
083
084  // Bulk Operations
085
086  /**
087   * {@inheritDoc}
088   *
089   * <p><b>Warning:</b> the results of calling this method may vary depending on the iteration order
090   * of {@code map}.
091   *
092   * @throws IllegalArgumentException if an attempt to {@code put} any entry fails. Note that some
093   *     map entries may have been added to the bimap before the exception was thrown.
094   */
095  @Override
096  void putAll(Map<? extends K, ? extends V> map);
097
098  // Views
099
100  /**
101   * {@inheritDoc}
102   *
103   * <p>Because a bimap has unique values, this method returns a {@link Set}, instead of the {@link
104   * java.util.Collection} specified in the {@link Map} interface.
105   */
106  @Override
107  Set<V> values();
108
109  /**
110   * Returns the inverse view of this bimap, which maps each of this bimap's values to its
111   * associated key. The two bimaps are backed by the same data; any changes to one will appear in
112   * the other.
113   *
114   * <p><b>Note:</b>There is no guaranteed correspondence between the iteration order of a bimap and
115   * that of its inverse.
116   *
117   * @return the inverse view of this bimap
118   */
119  BiMap<V, K> inverse();
120}