Why do some of my timers not execute their tasks at all?

Question

I'm developing a multi-timertask project.

First of all, I design some classes extended TimerTask and override the run() method. In the run() method, a line will be printed with current time.

Secondly, a Timer is initialized like this.

......
DataTask task1 = new DataTask();
myTaskList.add(task1);
DataTask task2 = new DataTask();
myTaskList.add(task2);
DataTask task3 = new DataTask();
myTaskList.add(task3);
DataTask task4 = new DataTask();
myTaskList.add(task4);

for(TimerTask task : myTaskList)
{
    Timer timer = new Timer();
    timer.schedule(task,1,60*1000);
}

......

public class DataTask extends TimerTask
{
     @override
     public void run()
     {
           System.out.println("print sth");
     }

}

One task in one thread. Is that Right?

Sometimes the tasks work, however, sometimes the tasks will not print anything, without any Exception, while the thread is still alive.

What could be the reason for this?