001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4;
018
019/**
020 * Defines a map that allows bidirectional lookup between key and values
021 * and retains and provides access to an ordering.
022 * <p>
023 * Implementations should allow a value to be looked up from a key and
024 * a key to be looked up from a value with equal performance.
025 * </p>
026 *
027 * @param <K> the type of the keys in the map
028 * @param <V> the type of the values in the map
029 *
030 * @since 3.0
031 */
032public interface OrderedBidiMap<K, V> extends BidiMap<K, V>, OrderedMap<K, V> {
033
034    /**
035     * Gets a view of this map where the keys and values are reversed.
036     * <p>
037     * Changes to one map will be visible in the other and vice versa.
038     * This enables both directions of the map to be accessed equally.
039     * <p>
040     * Implementations should seek to avoid creating a new object every time this
041     * method is called. See <code>AbstractMap.values()</code> etc. Calling this
042     * method on the inverse map should return the original.
043     * <p>
044     * Implementations must return an <code>OrderedBidiMap</code> instance,
045     * usually by forwarding to <code>inverseOrderedBidiMap()</code>.
046     *
047     * @return an inverted bidirectional map
048     */
049    @Override
050    OrderedBidiMap<V, K> inverseBidiMap();
051
052}