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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  import java.util.Comparator;
20  import java.util.SortedMap;
21  
22  /**
23   * Defines a map that allows bidirectional lookup between key and values
24   * and retains both keys and values in sorted order.
25   * <p>
26   * Implementations should allow a value to be looked up from a key and
27   * a key to be looked up from a value with equal performance.
28   * </p>
29   *
30   * @param <K> the type of the keys in the map
31   * @param <V> the type of the values in the map
32   * @since 3.0
33   */
34  public interface SortedBidiMap<K, V> extends OrderedBidiMap<K, V>, SortedMap<K, V> {
35  
36      /**
37       * Gets a view of this map where the keys and values are reversed.
38       * <p>
39       * Changes to one map will be visible in the other and vice versa.
40       * This enables both directions of the map to be accessed equally.
41       * <p>
42       * Implementations should seek to avoid creating a new object every time this
43       * method is called. See <code>AbstractMap.values()</code> etc. Calling this
44       * method on the inverse map should return the original.
45       * <p>
46       * Implementations must return a <code>SortedBidiMap</code> instance,
47       * usually by forwarding to <code>inverseSortedBidiMap()</code>.
48       *
49       * @return an inverted bidirectional map
50       */
51      @Override
52      SortedBidiMap<V, K> inverseBidiMap();
53  
54      /**
55       * Get the comparator used for the values in the value-to-key map aspect.
56       * @return Comparator&lt;? super V&gt;
57       */
58      Comparator<? super V> valueComparator();
59  }