ReentrantLock公平
ReentrantLock公平
提问于 2021-12-12 04:44:56
我的ReentrantLock不像我期望的那样工作。我期望下面代码的结果是随机锁定和解锁两个线程，但是我得到的结果总是在一个线程上解锁。有人能解释一下ReentrantLock吗?我正试图理解它的公平性策略(即新的ReentrantLock(true))和tryLock()方法。谢谢。
final ReentrantLock lock = new ReentrantLock(true);
new Thread(new Runnable() {
@Override
public void run() {
while (true)
try{
if (lock.tryLock(1, TimeUnit.SECONDS)) {
lock.lock();
System.out.println(Thread.currentThread().getName() + " locked");
lock.unlock();
} else {
System.out.println(Thread.currentThread().getName() + " not locked");
}
Thread.sleep(1000);
} catch (Exception e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
while (true)
try{
if (lock.tryLock(1, TimeUnit.SECONDS)) {
lock.lock();
System.out.println(Thread.currentThread().getName() + " locked");
lock.unlock();
} else {
System.out.println(Thread.currentThread().getName() + " not locked");
}
Thread.sleep(1000);
} catch (Exception e) {
e.printStackTrace();
}
}
}).start();控制台的结果：
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked
Thread-1 not locked
Thread-0 locked回答 1
Stack Overflow用户
回答已采纳
发布于 2021-12-12 06:12:05
你的用法坏了。您可以调用tryLock，它可能锁定也可能不锁(它返回的布尔值告诉您发生了什么)。
如果lock()工作正常，您可以立即将称为第二次，这很好，因为它是一个可重入的锁，但是现在您还需要调用unlock()两次，而不是这样做的。对lock() 的每一次呼叫和对** tryLock 的每一次调用都必须伴随着 unlock() 调用。
因此，无论哪个线程赢得了竞赛，都不会释放锁，因为您没有匹配您的锁调用。
考虑到您必须解锁，实际上只有一种方法可以使用锁定：
someLock.lock();
try {
do stuff here
} finally {
someLock.unlock();
}以及使用tryLock
if (someLock.tryLock()) try {
code goes here
} finally {
someLock.unlock();
} else {
code here if lock was not available
}如果您的锁调用没有紧接着关键字try，那么您的代码就会中断。注意，锁类的javadoc提到了这一点，并在所有相关示例中都显示了这一点。ReentrantLock javadoc -它就在上面。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/70320992
复制相关文章
相似问题
腾讯云开发者
