Question

I have a 2 processes to perform in my swing application, one to fill a list, and one to do operations on each element on the list. I’ve just moved the 2 processes into Swingworker threads to stop the GUI locking up while the tasks are performed, and because I will need to do this set of operations to several lists, so concurrency wouldn’t be a bad idea in the first place. However, when I just ran

fillList.execute();
doStuffToList.execute();

the doStuffToList thread to ran on the empty list (duh…). How do I tell the second process to wait until the first one is done? I suppose I could just nest the second process at the end of the first one, but i dunno, it seems like bad practice.

Answer 1

Something like this would do it, I think?

boolean listIsFull=false;
class FillListWorker extends SwingWorker<Foo,Bar>
{
    ...
    protected void done()
    {
        synchronized (listYouveBeenFilling)
        {
            listIsFull=true;
            listYouveBeenFilling.notifyAll();
        }
    }
    ...
}

class DoStuffToListListWorker extends SwingWorker<Foo,Bar>
{
    ...
    protected Foo doInBackground()
    {
        synchronized (listYouveBeenFilling)
        {
            while (!listIsFull)
            {
                try
                {
                    listYouveBeenFilling.wait();
                }
                catch (InterruptedException ie)
                {
                    // Don't worry, we'll just wait again
                }
            }
        }
    }
    ...
}