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}