    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    }