写锁优先访问java读写锁中的临界区？

问题描述

我需要写入线程优先于读取线程访问临界区，我可以使用 ReadWriteLock 接口来做到这一点吗？

解决方法

虽然不直接使用 ReadWriteLock，但最简单的内置方法可能是 Semaphore，它确实支持公平性。创建一个公平 Semaphore，（实际上）无限数量的 permis 就足够了：

private static final Semaphore lock = new Semaphore(Integer.MAX_VALUE,true);

public void doReadLocked() throws InterruptedException {

    // 'Read' lock only acquires one permit,but since there are A LOT,// many of them can run at once.
    lock.acquire();
    try {
        // Do your stuff in here...
    } finally {

        // Make sure you release afterwards.
        lock.release();
    }
}

public void doWriteLocked() throws InterruptedException {

    // 'Write' lock demands ALL the permits.  Since fairness is set,this
    // will 'take priority' over other waiting 'read'ers waiting to acquire
    // permits.
    lock.acquire(Integer.MAX_VALUE);
    try {
        // Do your stuff in here...
    } finally {

        // Make sure you release afterwards.
        lock.release(Integer.MAX_VALUE);
    }
}