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.