Java中的并发编程问题——死锁现象实例

原创川长思鸟来 2024-10-25 11:51 27阅读 0赞

死锁是Java并发编程中一个常见的问题，它发生在两个或更多的进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。

以下是一个简单的Java死锁例子：

```java
// 创建两个线程，每个线程持有资源A和B
class Thread1 extends Thread {
    private Object resourceA;
    private Object resourceB;

public Thread1(Object resourceA, Object resourceB) {
        this.resourceA = resourceA;
        this.resourceB = resourceB;
    }

@Override
    public void run() {
        synchronized (resourceA) {
            synchronized (resourceB) {
                System.out.println("Thread 1 acquired both resources.");
                // 死锁发生，每个线程都在等待对方释放资源
            }
        }
    }
}

class Thread2 extends Thread {
    private Object resourceA;
    private Object resourceB;

public Thread2(Object resourceA, Object resourceB) {
        this.resourceA = resourceA;
        this.resourceB = resourceB;
    }

@Override
    public void run() {
        synchronized (resourceA) {
            synchronized (resourceB) {
                System.out.println("Thread 2 acquired both resources.");
                // 此时每个线程都持有资源，互相等待对方释放资源
            }
        }
    }
}

public class DeadLockExample {
    public static void main(String[] args) {
        Thread1 thread1 = new Thread1(new Object(), new Object());
        Thread2 thread2 = new Thread2(new Object(), new Object()));

thread1.start();
        thread2.start();

try {
            // 线程会在此处阻塞，等待对方释放资源
            thread1.join();
            thread2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

System.out.println("Both threads have finished their execution.");
    }
}
```

在这个例子中，两个线程（Thread 1 和 Thread 2）同时竞争两份资源（resourceA 和 resourceB）。当每个线程获取资源后，它会等待对方释放资源。这样就形成了一个死锁，因为没有任何一个线程能够继续执行而不干扰其他线程。