    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.collections4;
    018
    019import java.util.Collection;
    020
    021/**
    022 * Defines a map that holds a collection of values against each key.
    023 * <p>
    024 * A <code>MultiMap</code> is a Map with slightly different semantics.
    025 * Putting a value into the map will add the value to a Collection at that key.
    026 * Getting a value will return a Collection, holding all the values put to that key.
    027 * <p>
    028 * For example:
    029 * <pre>
    030 * MultiMap mhm = new MultiValueMap();
    031 * mhm.put(key, "A");
    032 * mhm.put(key, "B");
    033 * mhm.put(key, "C");
    034 * Collection coll = (Collection) mhm.get(key);</pre>
    035 * <p>
    036 * <code>coll</code> will be a collection containing "A", "B", "C".
    037 * <p>
    038 * NOTE: Additional methods were added to this interface in Commons Collections 3.1.
    039 * These were added solely for documentation purposes and do not change the interface
    040 * as they were defined in the superinterface <code>Map</code> anyway.
    041 *
    042 * @param <K> the type of the keys in this map
    043 * @param <V> the type of the values in this map
    044 *
    045 * @since 2.0
    046 * @deprecated since 4.1, use {@link MultiValuedMap} instead
    047 */
    048@Deprecated
    049public interface MultiMap<K, V> extends IterableMap<K, Object> {
    050
    051    /**
    052     * Removes a specific value from map.
    053     * <p>
    054     * The item is removed from the collection mapped to the specified key.
    055     * Other values attached to that key are unaffected.
    056     * <p>
    057     * If the last value for a key is removed, implementations typically
    058     * return <code>null</code> from a subsequent <code>get(Object)</code>, however
    059     * they may choose to return an empty collection.
    060     *
    061     * @param key  the key to remove from
    062     * @param item  the item to remove
    063     * @return {@code true} if the mapping was removed, {@code false} otherwise
    064     * @throws UnsupportedOperationException if the map is unmodifiable
    065     * @throws ClassCastException if the key or value is of an invalid type
    066     * @throws NullPointerException if the key or value is null and null is invalid
    067     * @since 4.0 (signature in previous releases: V remove(K, V))
    068     */
    069    boolean removeMapping(K key, V item);
    070
    071    //-----------------------------------------------------------------------
    072    /**
    073     * Gets the number of keys in this map.
    074     * <p>
    075     * Implementations typically return only the count of keys in the map
    076     * This cannot be mandated due to backwards compatibility of this interface.
    077     *
    078     * @return the number of key-collection mappings in this map
    079     */
    080    @Override
    081    int size();
    082
    083    /**
    084     * Gets the collection of values associated with the specified key.
    085     * <p>
    086     * The returned value will implement <code>Collection</code>. Implementations
    087     * are free to declare that they return <code>Collection</code> subclasses
    088     * such as <code>List</code> or <code>Set</code>.
    089     * <p>
    090     * Implementations typically return <code>null</code> if no values have
    091     * been mapped to the key, however the implementation may choose to
    092     * return an empty collection.
    093     * <p>
    094     * Implementations may choose to return a clone of the internal collection.
    095     *
    096     * @param key  the key to retrieve
    097     * @return the <code>Collection</code> of values, implementations should
    098     *  return <code>null</code> for no mapping, but may return an empty collection
    099     * @throws ClassCastException if the key is of an invalid type
    100     * @throws NullPointerException if the key is null and null keys are invalid
    101     */
    102    @Override
    103    Object get(Object key); // Cannot use get(K key) as that does not properly implement Map#get
    104
    105    /**
    106     * Checks whether the map contains the value specified.
    107     * <p>
    108     * Implementations typically check all collections against all keys for the value.
    109     * This cannot be mandated due to backwards compatibility of this interface.
    110     *
    111     * @param value  the value to search for
    112     * @return true if the map contains the value
    113     * @throws ClassCastException if the value is of an invalid type
    114     * @throws NullPointerException if the value is null and null value are invalid
    115     */
    116    @Override
    117    boolean containsValue(Object value);
    118
    119    /**
    120     * Adds the value to the collection associated with the specified key.
    121     * <p>
    122     * Unlike a normal <code>Map</code> the previous value is not replaced.
    123     * Instead the new value is added to the collection stored against the key.
    124     * The collection may be a <code>List</code>, <code>Set</code> or other
    125     * collection dependent on implementation.
    126     *
    127     * @param key  the key to store against
    128     * @param value  the value to add to the collection at the key
    129     * @return typically the value added if the map changed and null if the map did not change
    130     * @throws UnsupportedOperationException if the map is unmodifiable
    131     * @throws ClassCastException if the key or value is of an invalid type
    132     * @throws NullPointerException if the key or value is null and null is invalid
    133     * @throws IllegalArgumentException if the key or value is invalid
    134     */
    135    @Override
    136    Object put(K key, Object value);
    137
    138    /**
    139     * Removes all values associated with the specified key.
    140     * <p>
    141     * Implementations typically return <code>null</code> from a subsequent
    142     * <code>get(Object)</code>, however they may choose to return an empty collection.
    143     *
    144     * @param key  the key to remove values from
    145     * @return the <code>Collection</code> of values removed, implementations should
    146     *  return <code>null</code> for no mapping found, but may return an empty collection
    147     * @throws UnsupportedOperationException if the map is unmodifiable
    148     * @throws ClassCastException if the key is of an invalid type
    149     * @throws NullPointerException if the key is null and null keys are invalid
    150     */
    151    @Override
    152    Object remove(Object key); // Cannot use remove(K key) as that does not properly implement Map#remove
    153
    154    /**
    155     * Gets a collection containing all the values in the map.
    156     * <p>
    157     * Implementations typically return a collection containing the combination
    158     * of values from all keys.
    159     * This cannot be mandated due to backwards compatibility of this interface.
    160     *
    161     * @return a collection view of the values contained in this map
    162     */
    163    @Override
    164    Collection<Object> values();
    165
    166}