- /*
- * Copyright 2003-2004 The Apache Software Foundation
- *
- * Licensed 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.collections;
-
- /**
- * Defines a map that allows bidirectional lookup between key and values.
- * <p>
- * This extended <code>Map</code> represents a mapping where a key may
- * lookup a value and a value may lookup a key with equal ease.
- * This interface extends <code>Map</code> and so may be used anywhere a map
- * is required. The interface provides an inverse map view, enabling
- * full access to both directions of the <code>BidiMap</code>.
- * <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.
- * <p>
- * This map enforces the restriction that there is a 1:1 relation between
- * keys and values, meaning that multiple keys cannot map to the same value.
- * This is required so that "inverting" the map results in a map without
- * duplicate keys. See the {@link #put} method description for more information.
- *
- * @since Commons Collections 3.0
- * @version $Revision: 1.16 $ $Date: 2004/05/10 20:37:19 $
- *
- * @author Stephen Colebourne
- */
- public interface BidiMap extends IterableMap {
-
- /**
- * Obtains a <code>MapIterator</code> over the map.
- * <p>
- * A map iterator is an efficient way of iterating over maps.
- * It does not require that the map is stored using Map Entry objects
- * which can increase performance.
- * <pre>
- * BidiMap map = new DualHashBidiMap();
- * MapIterator it = map.mapIterator();
- * while (it.hasNext()) {
- * Object key = it.next();
- * Object value = it.getValue();
- * it.setValue("newValue");
- * }
- * </pre>
- *
- * @return a map iterator
- */
- MapIterator mapIterator();
-
- /**
- * Puts the key-value pair into the map, replacing any previous pair.
- * <p>
- * When adding a key-value pair, the value may already exist in the map
- * against a different key. That mapping is removed, to ensure that the
- * value only occurs once in the inverse map.
- * <pre>
- * BidiMap map1 = new DualHashBidiMap();
- * map.put("A","B"); // contains A mapped to B, as per Map
- * map.put("A","C"); // contains A mapped to C, as per Map
- *
- * BidiMap map2 = new DualHashBidiMap();
- * map.put("A","B"); // contains A mapped to B, as per Map
- * map.put("C","B"); // contains C mapped to B, key A is removed
- * </pre>
- *
- * @param key the key to store
- * @param value the value to store
- * @return the previous value mapped to this key
- *
- * @throws UnsupportedOperationException if the <code>put</code> method is not supported
- * @throws ClassCastException (optional) if the map limits the type of the
- * value and the specified value is inappropriate
- * @throws IllegalArgumentException (optional) if the map limits the values
- * in some way and the value was invalid
- * @throws NullPointerException (optional) if the map limits the values to
- * non-null and null was specified
- */
- Object put(Object key, Object value);
-
- /**
- * Gets the key that is currently mapped to the specified value.
- * <p>
- * If the value is not contained in the map, <code>null</code> is returned.
- * <p>
- * Implementations should seek to make this method perform equally as well
- * as <code>get(Object)</code>.
- *
- * @param value the value to find the key for
- * @return the mapped key, or <code>null</code> if not found
- *
- * @throws ClassCastException (optional) if the map limits the type of the
- * value and the specified value is inappropriate
- * @throws NullPointerException (optional) if the map limits the values to
- * non-null and null was specified
- */
- Object getKey(Object value);
-
- /**
- * Removes the key-value pair that is currently mapped to the specified
- * value (optional operation).
- * <p>
- * If the value is not contained in the map, <code>null</code> is returned.
- * <p>
- * Implementations should seek to make this method perform equally as well
- * as <code>remove(Object)</code>.
- *
- * @param value the value to find the key-value pair for
- * @return the key that was removed, <code>null</code> if nothing removed
- *
- * @throws ClassCastException (optional) if the map limits the type of the
- * value and the specified value is inappropriate
- * @throws NullPointerException (optional) if the map limits the values to
- * non-null and null was specified
- * @throws UnsupportedOperationException if this method is not supported
- * by the implementation
- */
- Object removeValue(Object value);
-
- /**
- * 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 as a <code>Map</code>.
- * <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.
- *
- * @return an inverted bidirectional map
- */
- BidiMap inverseBidiMap();
-
- }