AtomicInitializer.java

/**
 * Copyright 2013-2016 Guoqiang Chen, Shanghai, China. All rights reserved.
 *
 *   Author: Guoqiang Chen
 *    Email: subchen@gmail.com
 *   WebURL: https://github.com/subchen
 *
 * 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.
 */
package jetbrick.util.concurrent;

import java.util.concurrent.atomic.AtomicReference;

public abstract class AtomicInitializer<T> implements ConcurrentInitializer<T> {
    private final AtomicReference<T> reference = new AtomicReference<T>();

    @Override
    public T get() {
        T result = reference.get();
        if (result == null) {
            result = initialize();
            if (!reference.compareAndSet(null, result)) {
                result = reference.get();
            }
        }
        return result;
    }

    protected abstract T initialize();
}