/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF 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 * * 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. */ package org.apache.commons.lang3.concurrent; import java.util.concurrent.atomic.AtomicReference; /** * A specialized implementation of the {@link ConcurrentInitializer} interface * based on an {@link AtomicReference} variable. * *
* This class maintains a member field of type {@link AtomicReference}. It * implements the following algorithm to create and initialize an object in its * {@link #get()} method: *
** Because atomic variables are used this class does not need any * synchronization. So there is no danger of deadlock, and access to the managed * object is efficient. However, if multiple threads access the {@code * AtomicInitializer} object before it has been initialized almost at the same * time, it can happen that {@link #initialize()} is called multiple times. The * algorithm outlined above guarantees that {@link #get()} always returns the * same object though. *
** Compared with the {@link LazyInitializer} class, this class can be more * efficient because it does not need synchronization. The drawback is that the * {@link #initialize()} method can be called multiple times which may be * problematic if the creation of the managed object is expensive. As a rule of * thumb this initializer implementation is preferable if there are not too many * threads involved and the probability that multiple threads access an * uninitialized object is small. If there is high parallelism, * {@link LazyInitializer} is more appropriate. *
* * @since 3.0 * @param