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 * @since 3.0
30 */
31 public interface OrderedBidiMap<K, V> extends BidiMap<K, V>, OrderedMap<K, V> {
32
33 /**
34 * Gets a view of this map where the keys and values are reversed.
35 * <p>
36 * Changes to one map will be visible in the other and vice versa.
37 * This enables both directions of the map to be accessed equally.
38 * </p>
39 * <p>
40 * Implementations should seek to avoid creating a new object every time this
41 * method is called. See {@code AbstractMap.values()} etc. Calling this
42 * method on the inverse map should return the original.
43 * </p>
44 * <p>
45 * Implementations must return an {@code OrderedBidiMap} instance,
46 * usually by forwarding to {@code inverseOrderedBidiMap()}.
47 * </p>
48 *
49 * @return an inverted bidirectional map
50 */
51 @Override
52 OrderedBidiMap<V, K> inverseBidiMap();
53
54 }