Java多线程并发中的死锁问题实例

原创迷南。 2024-12-08 17:54 20阅读 0赞

死锁是多线程并发中的一种严重问题，当两个或更多的线程在执行过程中因争夺资源而造成的一种互相等待的现象称为死锁。

下面是一个简单的死锁例子：

```java
// 线程A和B共享资源
class Resource {
    private boolean acquired = false;

public synchronized void acquire() {
        if (acquired) {
            throw new IllegalStateException("Resource is already acquired");
        }
        acquired = true;
        notifyAll();
    }

public synchronized void release() {
        if (!acquired) {
            throw new IllegalStateException("Resource is not acquired");
        }
        acquired = false;
        notifyAll();
    }
}

// 线程A获取资源，然后等待B
class ThreadA extends Thread {
    private Resource resource;

public ThreadA(Resource resource) {
        this.resource = resource;
    }

@Override
    public void run() {
        try {
            resource.acquire(); // A获取资源
            System.out.println("Thread A: Waiting for Thread B to release the resource");
            // A等待B释放资源
            resource.notifyAll();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

// 线程B获取资源，然后等待A释放资源
class ThreadB extends Thread {
    private Resource resource;

public ThreadB(Resource resource) {
        this.resource = resource;
    }

@Override
    public void run() {
        try {
            resource.acquire(); // B获取资源
            System.out.println("Thread B: Waiting for Thread A to release the resource");
            // B等待A释放资源
            resource.notifyAll();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public class DeadLockExample {
    public static void main(String[] args) {
        Resource resource = new Resource();

// 线程A和B按照死锁顺序执行
        ThreadA threadA = new ThreadA(resource);
        ThreadB threadB = new ThreadB(resource);

threadA.start();
        threadB.start();
    }
}
```

在这个例子中，线程A先获取资源并等待线程B释放资源。然后线程B同样获取资源并等待线程A释放资源。这样就形成了两个相互等待的循环，导致了死锁。