java - 如何在 TimerTask 执行时暂停主线程？

Question

package demo;

import java.util.Timer;
import java.util.TimerTask;

public class Demo {
    public static Timer timer = new Timer();

    static {
        MyTask task = new MyTask();
        timer.schedule(task, 1000);     
    }

    public static void main(String[] args) {
        System.out.println("Begin..."); 

        while (true) {
            // do something         
        }
    }

}

class MyTask extends TimerTask { 
    public void run() {
        // do something 

        MyTask task = new MyTask();
        Demo.timer.schedule(task, 1000);
    }
}

如何让 main 线程在 TimerTask 进入时暂停，并在它退出时恢复。

Answer 1

创建一个锁并等待 MyTask 设置 isFinished 标志并调用 lock.notify()

static Object lock = new Object();
static boolean isFinished;

public static void main(String[] args) throws Exception {
    System.out.println("Begin...");
    synchronized (lock) {
        while (!isFinished) {
            lock.wait();
        }
    }
}

注意 lock.wait() 需要在 while 循环中，Java 不保证你的线程只会被通知唤醒，参见 Object.wait API