src/main/java/org/apache/commons/collections4/SortedBidiMap.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.collections4;

import java.util.Comparator;
import java.util.SortedMap;

/**
 * Defines a map that allows bidirectional lookup between key and values
 * and retains both keys and values in sorted order.
 * <p>
 * Implementations should allow a value to be looked up from a key and
 * a key to be looked up from a value with equal performance.
 *
 * @param <K> the type of the keys in the map
 * @param <V> the type of the values in the map
 * @since 3.0
 * @version $Id$
 */
public interface SortedBidiMap<K, V> extends OrderedBidiMap<K, V>, SortedMap<K, V> {

    /**
     * Gets a view of this map where the keys and values are reversed.
     * <p>
     * Changes to one map will be visible in the other and vice versa.
     * This enables both directions of the map to be accessed equally.
     * <p>
     * Implementations should seek to avoid creating a new object every time this
     * method is called. See <code>AbstractMap.values()</code> etc. Calling this
     * method on the inverse map should return the original.
     * <p>
     * Implementations must return a <code>SortedBidiMap</code> instance,
     * usually by forwarding to <code>inverseSortedBidiMap()</code>.
     *
     * @return an inverted bidirectional map
     */
    @Override
    SortedBidiMap<V, K> inverseBidiMap();

    /**
     * Get the comparator used for the values in the value-to-key map aspect.
     * @return Comparator<? super V>
     */
    Comparator<? super V> valueComparator();
}