Java TimerTask取消不起作用

Question

Trying the TimerTask with ScheduledExecutorService. Schedule a task with delay 10 sec, and call task.cancel. But the task still run, not sure what happen, and if the cancel method doesn't seems to do any cancelling. Please help.

package xxx.xxx;

import java.util.TimerTask;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class Tester {

    static class OrderWaveTask extends TimerTask{
        public void run() {
            System.out.println("hi");
        }
    }

    public static void main(String[] args) {

        ScheduledExecutorService orderWaveTP = Executors.newScheduledThreadPool(3);
        TimerTask task = new Tester.OrderWaveTask();
        orderWaveTP.schedule(task, 10, TimeUnit.SECONDS);
        System.out.println("cancelling task: "+ task.cancel());
    }

}

Answer 1

You should use ScheduledFuture to cancel the task. Change your code to following should make it work.

ScheduledFuture<?> future = orderWaveTP.schedule(task, 10, TimeUnit.SECONDS);
System.out.println("cancelling task: "+ future.cancel(false));

Answer 2

The TimerTask is meant to be used with a Timer class in order to schedule executions and support cancellation.

When you schedule a TimerTask via an Executor, you're really just telling the executor to run a Runnable, and control is performed by the Executor; it has no idea that you're running a TimerTask, so the TimerTask functions have no effect.

Your choices would be to use a Timer instead of an ExecutorService, or use the ExecutorService methods to cancel execution.