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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.collections4;
18  
19  /**
20   * Defines a map that allows bidirectional lookup between key and values
21   * and retains and provides access to an ordering.
22   * <p>
23   * Implementations should allow a value to be looked up from a key and
24   * a key to be looked up from a value with equal performance.
25   * </p>
26   *
27   * @param <K> the type of the keys in the map
28   * @param <V> the type of the values in the map
29   *
30   * @since 3.0
31   */
32  public interface OrderedBidiMap<K, V> extends BidiMap<K, V>, OrderedMap<K, V> {
33  
34      /**
35       * Gets a view of this map where the keys and values are reversed.
36       * <p>
37       * Changes to one map will be visible in the other and vice versa.
38       * This enables both directions of the map to be accessed equally.
39       * <p>
40       * Implementations should seek to avoid creating a new object every time this
41       * method is called. See <code>AbstractMap.values()</code> etc. Calling this
42       * method on the inverse map should return the original.
43       * <p>
44       * Implementations must return an <code>OrderedBidiMap</code> instance,
45       * usually by forwarding to <code>inverseOrderedBidiMap()</code>.
46       *
47       * @return an inverted bidirectional map
48       */
49      @Override
50      OrderedBidiMap<V, K> inverseBidiMap();
51  
52  }