深入解析：Java多线程同步问题案例

原创系统管理员 2024-09-23 11:03 72阅读 0赞

Java多线程同步问题是由于多个线程同时访问共享资源，而这些资源的修改是需要特定条件或锁保护的。这就引出了如下的几种同步问题：

1. **竞态条件**：两个或更多的线程在没有适当锁定的情况下访问和修改同一资源。

```java
public class Counter {
    private int count = 0;

public synchronized void increment() {
        count++;
    }

public synchronized int decrement() {
        if (count > 0) {
            count--;
            return count;
        }
        throw new IllegalArgumentException("Cannot decrement to zero");
    }

public synchronized int getCount() {
        return count;
    }
}
```

2. **死锁**：两个或多个线程互相等待对方释放资源，导致都无法继续执行。

```java
public class DeadlockExample {
    private Object lock1 = new Object();
    private Object lock2 = new Object();

public void methodA() {
        synchronized (lock1) { // acquire lock1
            System.out.println("method A acquired lock1");
            try {
                Thread.sleep(500); // simulate long operation
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("method A released lock1");
            // now we can release lock1 before attempting to acquire lock2
        }

synchronized (lock2) { // acquire lock2
            System.out.println("method A acquired lock2");
            throw new RuntimeException("method A intentionally causing deadlock"); // simulate deadlock by throwing exception
        }
    }

public static void main(String[] args) {
        DeadlockExample example = new DeadlockExample();
        Thread threadA = new Thread(example::methodA));
        threadA.start();
    }
}
```

以上就是Java多线程同步问题的一个常见案例。在实际开发中，我们需要根据业务需求和可能存在的并发问题，灵活选择并正确使用锁、条件变量等同步工具。