CODEWITHSUNDEEP
javatimer
venkysmarty
venkysmarty

Reputation: 11431

multiple schedule calls with single timer

I am reading about timers in Java SDK 1.3

It is mentioned as follows in POSA volume 2 in active object pattern

JDK 1.3 introduced a mechansim for executing timer-based tasks concurrently in the classes java.util.Timer and java.util.TimerTask. When ever the scheduled execution time of a task occurs it is executed. The scheduling calls are executed in the clinets thread, while the tasks themselves are executed in a thread owned by Timer object. A timer internal task queue is protected by locks because the two threads outlined above operate on it concurrently.

The task queue is implemented as a priority queue so that the next TimerTask to expire can be identified efficiently. The timer thread simply waits until this expiration.

public class Reminder {
    Timer timer;

    public Reminder(int seconds) {
        timer = new Timer();
        timer.schedule(new RemindTask(), seconds*1000);
    }

    class RemindTask extends TimerTask {
        public void run() {
            System.out.format("Time's up!%n");
            timer.cancel(); //Terminate the timer thread
        }
    }

    public static void main(String args[]) {
        new Reminder(5);
        System.out.format("Task scheduled.%n");
    }
}

My question is

  1. Can we have multiple schedule functions with single timer? Request to give an example here and how it works. For example if we have two scheduled one task for every 5 seconds as shown above and another for every 12 seconds but I want to use same Reminder object instead of using another (i.e., creating) Reminder object. I want to know how internally it works like how timer stated like 5,5,2, 3, and so on . (as I have same kind of requirement in my project which I have to do in C++ with out using boost. I am planning to use single timer rather than multiple timers.

  2. What is delay argument here and how it is used. schedule(TimerTask task, long delay, long period)

Thanks for your time and help.

Upvotes: 0

Views: 2087

Answers (1)

Peter Lawrey
Peter Lawrey

Reputation: 533520

If you don't have to use SDK 1.3, you can use Java 5.0 which introduced the ScheduledExecutorService which makes Timers redundant IMHO.

The ScheduledExecutorService has been around more than 9 years, perhaps it is time to upgrade.

BTW 1.3 was end of lifed, before Sun officially had End of Life dates. It is ancient and unless you like history lessons, I suggest you live in the present. ;)

BTW Java 5.0 and Java 6 are both end of life and Java 7 will have its end of life date announced next year.

So I would look at Java 7 or 8 if I were you, and ignore anything which is more than a few years old because there are many practices which are either bad, or out dated on the Internet and they don't get updated.

If you like learning about bad or out of date practices, the rose india web site is the finest collection I have found. ;)

Upvotes: 1

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