Why doesn't this program terminate?

New to java, but I can't figure out why this program doesn't terminate:

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

class Main {
    public static void main(String[] args) {
        ScheduledExecutorService ex = Executors.newScheduledThreadPool(100);
        ex.submit(() -> { System.out.println("."); });
    }
}