You are modifying the set while you are iterating over it. This has nothing
to do with multi-threading.
Try something like...
Set<WidgetTask> tasks = widgetTaskSet.getAllTasks();
for(WidgetTask task: tasks) {
task.execute();
}
tasks.clear();
There are plenty more options too. Just don't modify the collection while
iterating over it.
Jason
On Mon, Jul 13, 2009 at 3:12 PM, Paul Sabou <paul.sa...@gmail.com> wrote:
>
> Hi,
>
> While running in hosted mode with GWT 1.6.4 I receive the following
> error :
>
> [ERROR] Uncaught exception escaped
> java.util.ConcurrentModificationException: null
> at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
> at java.util.HashMap$ValueIterator.next(HashMap.java:822)
> .......
>
>
> I tracked down the "offending block" :
> ---- BEGIN CODE ----
>
> Iterator<WidgetTask> taskIterator =
> widgetTaskSet
> .getAllTasks().iterator();
>
> // Execute Each Task
> while (taskIterator.hasNext()) {
> WidgetTask dwt = taskIterator.next();
> // Delete the task
> widgetTaskSet.deleteTask(dwt);
>
> // Execute the task goes here
>
> }
>
>
> ---- END CODE ----
>
> It seems that this block of code is executed somehow "in paralel" in
> hosted mode so that while some "thread" iterates over the structure,
> another one adds or deletes things from it. This behaviour is somewhat
> natural in any event driven app (including my own).
>
> I know that browsers are not multi-threaded, but the above scenario is
> also possible in a browser because my application does asyncronuous
> requests to the server.
>
> Is there any way to syncronise the block/data structure so that this
> doesn't happen anymore?
>
> >
>
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