javawhile-looptimertimertask

How to stop a Timer (util) with a while loop in Java?


Description: I am trying to stop the timer from running once i=10 with a while loop. This is only a test. In my project, I am actually going to use the timer to check a boolean value from an online database and stop the timer once "true" is returned.

Code:


public static void main(String[] args) {
    Timer timer = new Timer();

    TimerTask task = new TimerTask() {
        int i = 0;

        @Override
        public void run() {
            System.out.println("Timer ran for:" + ++i);
        }
    };

    while (i < 10) {
        timer.schedule(task, 0, 1000);
    }
}

Output:

Timer ran for:1
Exception in thread "main" java.lang.IllegalStateException: Task already scheduled or cancelled
    at java.base/java.util.Timer.sched(Timer.java:402)
    at java.base/java.util.Timer.schedule(Timer.java:249)
    at Code.testUtilTimer.main(testUtilTimer.java:31)
Timer ran for:2
Timer ran for:3
Timer ran for:4
Timer ran for:5
Timer ran for:6
Timer ran for:7
Timer ran for:8
Timer ran for:9
Timer ran for:10
Timer ran for:11

Solution

  • In my opinion you don't need to use while loop. Already schedule will work at certain time intervals. If you do as in my example, you will solve your problem.

     TimerTask task = new TimerTask() {
            public void run() {
                boolean dbValue = //Database operations
                if(dbValue) {
                  cancel();
                }
               
            }
        };
        Timer timer = new Timer("Timer");
        
        timer.scheduleAtFixedRate(task, 1000L, 1000L);