如何使用线程观察变量？

public class VariableObserver extends Thread {
    private volatile boolean observing; // 需要观察的变量
    private Object lock; // 同步锁

    public VariableObserver(Object lock) {
        this.lock = lock;
        observing = true;
    }

    public void stopObserving() {
        observing = false;
    }

    @Override
    public void run() {
        while (observing) {
            synchronized (lock) {
                // 输出变量的值
                System.out.println("Variable value: " + observing);
            }

            try {
                Thread.sleep(1000); // 每隔1秒观察一次
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Object lock = new Object(); // 同步锁
        VariableObserver observer = new VariableObserver(lock);

        observer.start(); // 启动观察线程

        // 在主线程中修改变量的值
        synchronized (lock) {
            observer.stopObserving();
        }

        observer.join(); // 等待观察线程执行完毕
    }
}