com.alibaba.tmq.common.domain.remoting.SemaphoreReleaseOnlyOnce Maven / Gradle / Ivy

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/**
 * Copyright (C) 2010-2013 Alibaba Group Holding Limited
 *
 * 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 com.alibaba.tmq.common.domain.remoting;

import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicBoolean;


/**
 * 使用布尔原子变量，信号量保证只释放一次
 * 
 * @author shijia.wxr
 * @since 2013-7-13
 */
public class SemaphoreReleaseOnlyOnce {
    private final AtomicBoolean released = new AtomicBoolean(false);
    private final Semaphore semaphore;


    public SemaphoreReleaseOnlyOnce(Semaphore semaphore) {
        this.semaphore = semaphore;
    }


    public void release() {
        if (this.semaphore != null) {
            if (this.released.compareAndSet(false, true)) {
                this.semaphore.release();
            }
        }
    }


    public Semaphore getSemaphore() {
        return semaphore;
    }
}