java - 使用 java.util.Timer 后程序不会终止

Question

我有简单的Timer控制台应用程序。为什么这个应用程序在执行 run 过程后没有停止并且仍在等待某些东西？

package timer_old;
import java.util.Timer;
import java.util.TimerTask;



public final class FetchMail extends TimerTask {

  public static void main (String[] args) 
  {
    System.out.println("starting");
    TimerTask fetchMail = new FetchMail();
    Timer timer = new Timer();
    timer.schedule(fetchMail, 500);
    //timer.cancel();
    System.out.println("exiting");
  }

  public void run()
  {
    System.out.println("Fetching mail...");
  }


}

输出:

starting
exiting
Fetching mail...

Answer 1

来自the docs :

By default, the task execution thread does not run as a daemon thread, so it is capable of keeping an application from terminating. If a caller wants to terminate a timer's task execution thread rapidly, the caller should invoke the timer's cancel method.