Here you can find the source of putIfAbsent(ConcurrentMap
Parameter | Description |
---|---|
map | The map |
key | The key |
value | The value to put |
public static <K, V> V putIfAbsent(ConcurrentMap<K, V> map, K key, V value)
//package com.java2s; /**//from ww w . j av a 2 s .co m * Licensed to Apereo under one or more contributor license * agreements. See the NOTICE file distributed with this work * for additional information regarding copyright ownership. * Apereo licenses this file to you 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 the following location: * * 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.concurrent.ConcurrentMap; public class Main { /** * How putIfAbsent should work, returns the one value that actually ends up in the {@link ConcurrentMap} * * @param map The map * @param key The key * @param value The value to put * @return The value that exists in the Map for this key at the point in time that {@link ConcurrentMap#putIfAbsent(Object, Object)} is called */ public static <K, V> V putIfAbsent(ConcurrentMap<K, V> map, K key, V value) { final V existingValue = map.putIfAbsent(key, value); if (existingValue == null) { return value; } return existingValue; } }