infinite loop through a list, enumeration

Question

So im building an application in swing that will ping a url or a list of urls to show the machines status. So if a machine disconnects it will show up as disconnected. I have a list of machines but I need it to loop over forever in intervals so I can know the status of the machine. I know you cant reset the enumeration count so im stuck on a workaround for it.

Currently the part of the code that does the pinging and enumeration is below:

class WorkerThread extends Thread { 
DefaultListModel model;

public WorkerThread(DefaultListModel aModel) { 
    model = aModel; 
} 

public void run() { 
Pinging ping = new Pinging();
int num ;
Enumeration<String> e;


for ( e= model.elements(), num=0; e.hasMoreElements(); num ++){
    String element = e.nextElement();
    for (int i = 0; i<5; i++){
    ping.reachUrl(element);
      //ping.timer(5, e.nextElement()); 
        final int pos = num;
        EventQueue.invokeLater(new Runnable() { 
            public void run() { 
                //ping.reachUrl(e.nextElement());
                String name = ping.getName();
                String addr = ping.getAddr();
                boolean reach = ping.getReach();
                int time = ping.getTime();
                model.set(pos, name+"  " + addr+"  " + reach + "  " + time);
                //model.add(pos, name+"  " + addr+"  " + reach + "  " + time);
                //model.set(pos, "Hello");

            } 
        }); 

        yield(); 
    }



}

} 

}

Answer 1

Use a List rather than an Enumeration .

Maintain an int that records your place in the list, and when you get to the end of the list, start again at the beginning.

But really you want a separate thread for each URL that you're watching. And you certainly don't want to be doing the ping calls on the event thread. Use a SwingWorker , so that it can run in the background and still update the GUI using the done() method when it's finished.