Is it safe to store timer instances in a map?

let's say I have lot of timers defined in the app.

@Startup
@Singleton
public class ScheduleManager {

    @Resource
    TimerService timerService;

    Map<Long, Timer> timerMap;

    @PostConstruct
    void init() {
        timerMap = new HashMap<>();
        for (int i = 0; i < 10; i++) {
            TimerConfig tc = new TimerConfig("someEntityId", true);
            Timer timer = timerService.createSingleActionTimer(new Date(TimeUnit.DAYS.toMillis(i)), tc);
            timerMap.put((long) i, timer);
        }
    }

    public void cancelTimerById(long i) {
        Timer timer = timerMap.get(i);
        if(timer != null) {
            timerMap.remove(i); //release the reference from Map
            timer.cancel();
        }
    } 
}

Is it safe/possible to cancel timers like that?

On other solution would be:

public void cancelTimerById(long i) {
        for(Timer timer : timerService.getTimers()) {
            if(Long.valueOf(timer.getInfo().toString()).equals(i)) {
                timer.cancel();
            }
        }
    }

But this is a bit too much iteration for each canceling...

My concern is keeping the instances of singleActionTimers (or other periodical timers) in a map. (for GC clean up).

Thanks