Java ConcurrentMap addIfAbsent(K key, ConcurrentMap map, Object value)

Description

add If Absent

License

Apache License

Return

if entry created return 0. if replace old entry return 1, if exist value return -1;

Declaration

public static <K> int addIfAbsent(K key, ConcurrentMap<K, Object[]> map, Object value) 

Method Source Code

//package com.java2s;
/*//from   w  w  w .j a va2s . c om
 * Copyright 2009 zaichu xiao
 *
 * 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.concurrent.ConcurrentMap;

public class Main {
    /**
     * @return if entry created return 0. if replace old entry return 1, if
     *         exist value return -1;
     * 
     */
    public static <K> int addIfAbsent(K key, ConcurrentMap<K, Object[]> map, Object value) {
        for (;;) {
            Object[] newElements, elements = map.get(key);
            if (elements == null && (elements = map.putIfAbsent(key, new Object[] { value })) == null)
                return 0;
            int i, len = i = elements.length;
            while (--i >= 0) {
                if (value.equals(elements[i]))
                    return -1;
            }
            (newElements = new Object[len + 1])[len] = value;
            while (--len >= 0)
                newElements[len] = elements[len];
            if (map.replace(key, elements, newElements))
                return 1;
        }
    }
}

Related

1. addClassMapping(String className, Class clazz)
2. addConcurrent(K key, C values, ConcurrentMap map)
3. clearClassMapping()
4. clearDefaultResourceBundles()
5. create(boolean sorted)
6. createConcurrentMap()