Update JProgressBar from ExecutorService

Question

I am pinging gateways using Java ICMP ping function. To perform fast pinging I am using ExectorService which creates threads for pinging. After address is pinged (or not) I want to update Jprogressbar after pinging. I have this code which is working but it updates Jprogressbar before job (ping thread) is finished. I want to update jprogressbar after job is finished.

private int NUM_THREADS = Runtime.getRuntime().availableProcessors();
ExecutorService exec = Executors.newFixedThreadPool(NUM_THREADS);
public void run() {
    int JProgressBarValue = 0;
    for (;GateWayKey<=GateWayKeyStop;GateWayKey++){
        ip="192.168."+GateWayKey+".1";
       exec.submit((new PingTask(ip,GateWayKey,true,scanFrameRefrence,ttl)));
       JProgressBarValue=(GateWayKey/GateWayKeyStop)*100;
       scanFrameRefrence.progressBar.setValue(JProgressBarValue);
       scanFrameRefrence.progressBar.repaint();
    }}

Answer 1

First of all, Swing components may not be used from outside of the event dispatch thread. So, the code updating the progress bar must be enclosed inside

SwingUtilities.invokeLater(new Runnable() {
    @Override
    public void run() {
        scanFrameRefrence.progressBar.setValue(value);
    }
});

Now, to answer the question. If you want to update the progress bar when a task finishes, the easier way is to have the task itself update the progress bar when at the end of its execution.

Another way is to use an ExecutorCompletionService, which can be notified (thanks to a blocking queue) when each task has finished.

Also, consider posting actual, compiling code, and respecting Java naming conventions: variables start with a lower-case letter.