java - 所有线程都获得锁？

Question

获取锁后，线程应 hibernate 一定时间(本例中为 6000ms)，以防止另一个线程获取锁。当我使用 l1.lock() 方法时，它工作正常，但是当我使用 l1.tryLock() 或 l1.tryLock(1000,TimeUnit.MILLISECOND) 时，两个线程都在前一个线程释放锁之前获取锁。怎么可能？

import java.util.concurrent.locks.*;
import java.util.concurrent.locks.Lock;

class MyLocks implements Runnable {
  static Lock l1;

  public static void main(String... asd) {
    l1 = new ReentrantLock();
    MyLocks obj = new MyLocks();
    new Thread(obj).start();
    new Thread(obj).start();
  }

  public void run() {
    System.out.println(Thread.currentThread().getName() + " is try to acquire lock");
    try {
      l1.trylock();
     // only those thread which has acquired lock will get here. 
      System.out.println(Thread.currentThread().getName() + " has acquired lock");

      Thread.sleep(6000);

    } catch (Exception e) {
    }
    l1.unlock();
  }
}

Answer 1

一个常见的错误是调用方法并忽略结果。您很可能正在运行

lock.tryLock(); // notice this ignores whether the lock was obtained or not.

当你应该做类似的事情时

while(!lock.tryLock(1, TimeUnit.SECOND)) {
  System.out.println(Thread.currentThread().getName()+" - Couldn't get lock, waiting");
}

注意:不要丢弃异常，除非您非常确信它们不重要。

}catch(Exception e){} // something when wrong but lets pretend it didn't

有关如何处理异常的一些提示。

https://vanilla-java.github.io/2016/06/21/Reviewing-Exception-Handling.html