Timer already cancelled
java, multithreading, timer, timertask
Solution
Immediately after scheduling all the timers, you cancel them. This doesn't work like the `ExecutorService` where you can schedule all you need and then call `shutdown`—this actually cancels the timer and all scheduled tasks.
Another problem with your code is that you call `System.exit` right away, not giving any chance to the scheduled tasks to actually run.
Apart from those problems, you may get a `Timer already canceled` exception if a previous task threw an exception. The exception will not be seen anywhere, but it will cancel the timer. Be sure to wrap your timer tasks into a catch-all try-statement.
Problem
I have two timers to manage input(en-queue) and output (dequeue) from a FIFO queue but I keep getting a exception for the dequeueing java.lang.IllegalStateException: Timer already cancelled. I can't place a stop to debug line where the error is claimed to occur line 83. I don't know what I'm missing so any help would be appreciated. ``` import java.util.Random; import java.util.Timer; import java.util.TimerTask; /** * RunSim */ public class RunSim { private double arrivalRate = 600; private double y; private Timer t; private Timer t2; private Queue fifoQueue; private long xy; private long fact = 10; private int count; private int pId; public RunSim() { Random r = new Random(); long n = System.currentTimeMillis(); r.setSeed(n); double i = r.nextDouble(); y = ((1 / arrivalRate) * (Math.log(i))); xy = (long) y; t = new Timer(); t2 = new Timer(); fifoQueue = new Queue(); count = 0; pId = 0; } public static void main() { RunSim rs = new RunSim(); rs.start(); } public void start() { class sendPacket extends TimerTask { public void run() { Packet p = new Packet(); p.setId(pId); fifoQueue.insert(p); p.setArrivalTime(); System.out.println("ID: " + p.getId() + " Arrival Time: " + p.getArrivalTime() / fact); pId++; } } class removePacket extends TimerTask { public void run() { fifoQueue.first().setDepartureTime(); System.out.println("ID: " + fifoQueue.first().getId() + " Departure Time: " + fifoQueue.first().getDepartureTime() / fact); fifoQueue.remove(); } } while (count < 1000) { long v = fact * (1 + Math.abs(xy)); t.schedule(new sendPacket(), 0, v); count++; t2.schedule(new removePacket(), 5, 5); } } } ```