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 (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    }