Java Collection Add addTo(Map> map, K key, V value)

License

Declaration

public static <K, V> void addTo(Map<K, Collection<V>> map, K key, V value) 

Method Source Code

//package com.java2s;
/*/*  www.  java 2  s .  c  o m*/
 Copyright (C) 2012 The Stanford MobiSocial Laboratory
    
   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.
*/

import java.util.*;

public class Main {
    /** takes in a map K,List<V> and adds value to key's list - effectively a multi-map. */
    public static <K, V> void addTo(Map<K, Collection<V>> map, K key, V value) {
        Collection<V> values = map.get(key);
        if (values == null) {
            values = new ArrayList<V>();
            map.put(key, values);
        }
        values.add(value);
    }
}

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