使用Java处理并发问题：死锁示例

原创傷城~ 2024-10-20 07:06 40阅读 0赞

死锁在并发编程中是一个常见的问题。简单来说，死锁是两个或更多进程因争夺资源而造成的一种互相等待的现象，若无外力干涉，它们都将无法继续执行。

以下是一个简单的Java死锁示例：

```java
// 假设我们有四个线程，每个都需要两个资源

class Resource {
    int count;
    boolean free = true;

public Resource(int count) {
        this.count = count;
    }

public synchronized void acquire() throws InterruptedException {
        while (!free) {
            wait();
        }
        free = false;
        count--;
    }

public synchronized void release() throws InterruptedException {
        if (free) {
            throw new IllegalStateException("Resource is not acquired");
        }
        free = true;
        count++;
    }
}

class Thread1 extends Thread {
    Resource res1, res2;

public Thread1(Resource res1, Resource res2) {
        this.res1 = res1;
        this.res2 = res2;
    }

@Override
    public void run() {
        try {
            res1.acquire();
            res2.acquire();
            System.out.println("Thread 1: Acquired both resources");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            try {
                res2.release();
                res1.release();
                System.out.println("Thread 1: Released both resources");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Resource res1 = new Resource(2);
        Resource res2 = new Resource(2);

Thread thread1 = new Thread1(res1, res2);
        thread1.start();

try {
            thread1.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
```

在这个例子中，四个线程分别需要两个资源。当线程1尝试获取资源1和2时，如果此时线程2还未释放资源2（即资源1已被线程2占用），那么就形成了死锁。