    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} 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 * <p>
    029 * For example:
    030 * </p>
    031 * <pre>
    032 * MultiMap mhm = new MultiValueMap();
    033 * mhm.put(key, "A");
    034 * mhm.put(key, "B");
    035 * mhm.put(key, "C");
    036 * Collection coll = (Collection) mhm.get(key);</pre>
    037 * <p>
    038 * {@code coll} will be a collection containing "A", "B", "C".
    039 * </p>
    040 * <p>
    041 * NOTE: Additional methods were added to this interface in Commons Collections 3.1.
    042 * These were added solely for documentation purposes and do not change the interface
    043 * as they were defined in the superinterface {@code Map} anyway.
    044 * </p>
    045 *
    046 * @param <K> the type of the keys in this map
    047 * @param <V> the type of the values in this map
    048 *
    049 * @since 2.0
    050 * @deprecated since 4.1, use {@link MultiValuedMap} instead
    051 */
    052@Deprecated
    053public interface MultiMap<K, V> extends IterableMap<K, Object> {
    054
    055    /**
    056     * Checks whether the map contains the value specified.
    057     * <p>
    058     * Implementations typically check all collections against all keys for the value.
    059     * This cannot be mandated due to backwards compatibility of this interface.
    060     *
    061     * @param value  the value to search for
    062     * @return true if the map contains the value
    063     * @throws ClassCastException if the value is of an invalid type
    064     * @throws NullPointerException if the value is null and null value are invalid
    065     */
    066    @Override
    067    boolean containsValue(Object value);
    068
    069    /**
    070     * Gets the collection of values associated with the specified key.
    071     * <p>
    072     * The returned value will implement {@code Collection}. Implementations
    073     * are free to declare that they return {@code Collection} subclasses
    074     * such as {@code List} or {@code Set}.
    075     * <p>
    076     * Implementations typically return {@code null} if no values have
    077     * been mapped to the key, however the implementation may choose to
    078     * return an empty collection.
    079     * <p>
    080     * Implementations may choose to return a clone of the internal collection.
    081     *
    082     * @param key  the key to retrieve
    083     * @return the {@code Collection} of values, implementations should
    084     *  return {@code null} for no mapping, but may return an empty collection
    085     * @throws ClassCastException if the key is of an invalid type
    086     * @throws NullPointerException if the key is null and null keys are invalid
    087     */
    088    @Override
    089    Object get(Object key); // Cannot use get(K key) as that does not properly implement Map#get
    090
    091    /**
    092     * Adds the value to the collection associated with the specified key.
    093     * <p>
    094     * Unlike a normal {@code Map} the previous value is not replaced.
    095     * Instead, the new value is added to the collection stored against the key.
    096     * The collection may be a {@code List}, {@code Set} or other
    097     * collection dependent on implementation.
    098     *
    099     * @param key  the key to store against
    100     * @param value  the value to add to the collection at the key
    101     * @return typically the value added if the map changed and null if the map did not change
    102     * @throws UnsupportedOperationException if the map is unmodifiable
    103     * @throws ClassCastException if the key or value is of an invalid type
    104     * @throws NullPointerException if the key or value is null and null is invalid
    105     * @throws IllegalArgumentException if the key or value is invalid
    106     */
    107    @Override
    108    Object put(K key, Object value);
    109
    110    /**
    111     * Removes all values associated with the specified key.
    112     * <p>
    113     * Implementations typically return {@code null} from a subsequent
    114     * {@code get(Object)}, however they may choose to return an empty collection.
    115     *
    116     * @param key  the key to remove values from
    117     * @return the {@code Collection} of values removed, implementations should
    118     *  return {@code null} for no mapping found, but may return an empty collection
    119     * @throws UnsupportedOperationException if the map is unmodifiable
    120     * @throws ClassCastException if the key is of an invalid type
    121     * @throws NullPointerException if the key is null and null keys are invalid
    122     */
    123    @Override
    124    Object remove(Object key); // Cannot use remove(K key) as that does not properly implement Map#remove
    125
    126    /**
    127     * Removes a specific value from map.
    128     * <p>
    129     * The item is removed from the collection mapped to the specified key.
    130     * Other values attached to that key are unaffected.
    131     * <p>
    132     * If the last value for a key is removed, implementations typically
    133     * return {@code null} from a subsequent {@code get(Object)}, however
    134     * they may choose to return an empty collection.
    135     *
    136     * @param key  the key to remove from
    137     * @param item  the item to remove
    138     * @return {@code true} if the mapping was removed, {@code false} otherwise
    139     * @throws UnsupportedOperationException if the map is unmodifiable
    140     * @throws ClassCastException if the key or value is of an invalid type
    141     * @throws NullPointerException if the key or value is null and null is invalid
    142     * @since 4.0 (signature in previous releases: V remove(K, V))
    143     */
    144    boolean removeMapping(K key, V item);
    145
    146    /**
    147     * Gets the number of keys in this map.
    148     * <p>
    149     * Implementations typically return only the count of keys in the map
    150     * This cannot be mandated due to backwards compatibility of this interface.
    151     *
    152     * @return the number of key-collection mappings in this map
    153     */
    154    @Override
    155    int size();
    156
    157    /**
    158     * Gets a collection containing all the values in the map.
    159     * <p>
    160     * Implementations typically return a collection containing the combination
    161     * of values from all keys.
    162     * This cannot be mandated due to backwards compatibility of this interface.
    163     *
    164     * @return a collection view of the values contained in this map
    165     */
    166    @Override
    167    Collection<Object> values();
    168
    169}