优雅地替代 thread.sleep

在 Java 中，可以使用 wait() 和 notify() 方法来替代 thread.sleep()。wait() 方法会让当前线程进入等待状态，直到另一个线程调用 notify() 方法来唤醒它。这种方式可以避免线程空转浪费 CPU 资源，提高程序效率。

以下是一个简单的例子：

public class WaitNotifyExample {
    public static void main(String[] args) {
        Object lock = new Object();
        Thread t1 = new Thread(new WaitThread(lock));
        Thread t2 = new Thread(new NotifyThread(lock));
        t1.start();
        t2.start();
    }
}

class WaitThread implements Runnable {
    private Object lock;

    public WaitThread(Object lock) {
        this.lock = lock;
    }

    public void run() {
        synchronized (lock) {
            try {
                System.out.println("WaitThread is waiting...");
                lock.wait();
                System.out.println("WaitThread is awake!");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

class NotifyThread implements Runnable {
    private Object lock;

    public NotifyThread(Object lock) {
        this.lock = lock;
    }

    public void run() {
        synchronized (lock) {
            try {
                System.out.println("NotifyThread is sleeping...");
                Thread.sleep(5000);
                lock.notify();
                System.out.println("NotifyThread sent notification!");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

在这个例子中，WaitThread 会在 lock 上等待，直到 NotifyThread 调用 lock.notify() 方法唤醒它。NotifyThread 在睡眠 5 秒后，调用 lock.notify() 方法发送通知。这样，WaitThread 就会被唤醒，继续执行。