    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 *      https://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 */
    017
    018package org.apache.commons.collections4;
    019
    020import java.util.Collection;
    021
    022/**
    023 * Defines a map that holds a collection of values against each key.
    024 * <p>
    025 * A {@code MultiMap} is a Map with slightly different semantics. Putting a value into the map will add the value to a Collection at that key. Getting a value
    026 * will return a Collection, holding all the values put to that key.
    027 * </p>
    028 * <p>
    029 * For example:
    030 * </p>
    031 *
    032 * <pre>
    033 * MultiMap mhm = new MultiValueMap();
    034 * mhm.put(key, "A");
    035 * mhm.put(key, "B");
    036 * mhm.put(key, "C");
    037 * Collection coll = (Collection) mhm.get(key);
    038 * </pre>
    039 * <p>
    040 * {@code coll} will be a collection containing "A", "B", "C".
    041 * </p>
    042 * <p>
    043 * NOTE: Additional methods were added to this interface in Commons Collections 3.1. These were added solely for documentation purposes and do not change the
    044 * interface as they were defined in the superinterface {@code Map} anyway.
    045 * </p>
    046 *
    047 * @param <K> The type of the keys in this map.
    048 * @param <V> The type of the values in this map.
    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. This cannot be mandated due to backwards compatibility of this interface.
    059     * </p>
    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 are free to declare that they return {@code Collection} subclasses such as
    073     * {@code List} or {@code Set}.
    074     * </p>
    075     * <p>
    076     * Implementations typically return {@code null} if no values have been mapped to the key, however the implementation may choose to return an empty
    077     * collection.
    078     * </p>
    079     * <p>
    080     * Implementations may choose to return a clone of the internal collection.
    081     * </p>
    082     *
    083     * @param key The key to retrieve.
    084     * @return The {@code Collection} of values, implementations should 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. Instead, the new value is added to the collection stored against the key. The collection
    095     * may be a {@code List}, {@code Set} or other collection dependent on implementation.
    096     * </p>
    097     *
    098     * @param key   The key to store against.
    099     * @param value The value to add to the collection at the key.
    100     * @return typically the value added if the map changed and null if the map did not change.
    101     * @throws UnsupportedOperationException if the map is unmodifiable.
    102     * @throws ClassCastException            if the key or value is of an invalid type.
    103     * @throws NullPointerException          if the key or value is null and null is invalid.
    104     * @throws IllegalArgumentException      if the key or value is invalid.
    105     */
    106    @Override
    107    Object put(K key, Object value);
    108
    109    /**
    110     * Removes all values associated with the specified key.
    111     * <p>
    112     * Implementations typically return {@code null} from a subsequent {@code get(Object)}, however they may choose to return an empty collection.
    113     * </p>
    114     *
    115     * @param key The key to remove values from.
    116     * @return The {@code Collection} of values removed, implementations should return {@code null} for no mapping found, but may return an empty collection.
    117     * @throws UnsupportedOperationException if the map is unmodifiable.
    118     * @throws ClassCastException            if the key is of an invalid type.
    119     * @throws NullPointerException          if the key is null and null keys are invalid.
    120     */
    121    @Override
    122    Object remove(Object key); // Cannot use remove(K key) as that does not properly implement Map#remove
    123
    124    /**
    125     * Removes a specific value from map.
    126     * <p>
    127     * The item is removed from the collection mapped to the specified key. Other values attached to that key are unaffected.
    128     * </p>
    129     * <p>
    130     * If the last value for a key is removed, implementations typically return {@code null} from a subsequent {@code get(Object)}, however they may choose to
    131     * return an empty collection.
    132     * </p>
    133     *
    134     * @param key  The key to remove from.
    135     * @param item The item to remove.
    136     * @return {@code true} if the mapping was removed, {@code false} otherwise.
    137     * @throws UnsupportedOperationException if the map is unmodifiable.
    138     * @throws ClassCastException            if the key or value is of an invalid type.
    139     * @throws NullPointerException          if the key or value is null and null is invalid.
    140     * @since 4.0 (signature in previous releases: V remove(K, V)).
    141     */
    142    boolean removeMapping(K key, V item);
    143
    144    /**
    145     * Gets the number of keys in this map.
    146     * <p>
    147     * Implementations typically return only the count of keys in the map This cannot be mandated due to backwards compatibility of this interface.
    148     * </p>
    149     *
    150     * @return The number of key-collection mappings in this map.
    151     */
    152    @Override
    153    int size();
    154
    155    /**
    156     * Gets a collection containing all the values in the map.
    157     * <p>
    158     * Implementations typically return a collection containing the combination of values from all keys. This cannot be mandated due to backwards compatibility
    159     * of this interface.
    160     * </p>
    161     *
    162     * @return A collection view of the values contained in this map.
    163     */
    164    @Override
    165    Collection<Object> values();
    166}