Java多线程并发：死锁实例与解决策略

原创 Bertha 。 2024-09-05 23:54 95阅读 0赞

在Java多线程编程中，死锁是一个常见的并发问题。简单来说，死锁发生在两个或多个线程互相等待对方释放资源的情况下，系统无法继续执行任何任务。

以下是一个死锁的Java实例：

```java
class Lock {
    private boolean locked = false;

public synchronized void lock() {
        if (locked) {
            throw new RuntimeException("Lock is already held");
        }
        locked = true;
    }

public synchronized void unlock() {
        if (!locked) {
            throw new RuntimeException("Lock is not held");
        }
        locked = false;
    }
}

class DeadlockExample {
    private final Lock lock1, lock2;

public DeadlockExample(Lock lock1, Lock lock2) {
        this.lock1 = lock1;
        this.lock2 = lock2;
    }

public void acquireLock1() {
        try {
            lock1.lock();
        } catch (Exception e) {
            // Handle exception
            System.out.println("Error acquiring lock 1: " + e.getMessage());
        }
    }

public void acquireLock2() {
        try {
            lock2.lock();
        } catch (Exception e) {
            // Handle exception
            System.out.println("Error acquiring lock 2: " + e.getMessage());
        }
    }

public static void main(String[] args) {
        Lock lock1 = new Lock();
        Lock lock2 = new Lock();

DeadlockExample example = new DeadlockExample(lock1, lock2);

// Example of a deadlock
        example.acquireLock1();
        example.acquireLock2();

// Wait for locks to be released by the example instance
        while (example.lock1.isLocked() || example.lock2.isLocked()) {
            try {
                Thread.sleep(50); // Sleep briefly before checking again
            } catch (InterruptedException e) {
                System.out.println("Interrupted while sleeping: " + e.getMessage());
                Thread.currentThread().interrupt();
            }
        }

// Example of releasing locks manually
        example.unlockLock1();
        example.unlockLock2();

System.out.println("Deadlock resolved. Locks released.");
    }
}
```

解决死锁的策略通常包括：

1. **预防死锁**：在创建资源分配图时，确保不存在形成死锁的循环。

2. **避免使用共享资源**：如果可能，尽量让线程独占资源，而不是共享。

3. **设定超时机制**：当一个线程等待其他线程释放资源而无法继续执行时，可以设置超时时间，若超时仍无法解决问题，则中断相关线程。

4. **使用死锁检测工具**：这些工具可以在运行时监控系统状态，发现并解决潜在的死锁问题。