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Kevin Dean · Guest

The "Reset" button is a hard reset; it shuts down the JVM unconditionally,
so your hook won't get called. It's basically there as a last resort in
case the application won't exit normally.

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"alan jeeves" <fake (AT) fake (DOT) com> wrote

alan jeeves · Guest

Thanks but how can i shut it down nicely? Ctrl-C doesnt work and its not a
GUI application

"Kevin Dean" <NkOdSePaAnM (AT) datadevelopment (DOT) com> wrote

Kevin Dean · Guest

The slightly-less-than-brute-force way is to call System.exit(0). More
correctly, an application terminates when all user threads terminate.

The main thread (the one with the "public static void main(String[] args)"
entry point) is a user thread. If your code falls through to the end of the
main() method, that thread terminates. If there are no other user threads,
your application will terminate. To try it, create a simple class as
follows:

public class TestClass {
public static void main(String[] args) {
System.out.println("Hello, world");
}
}

If you run that class, it will print the message in JBuilder's message pane
and exit immediately.

If, on the other hand, your main() method spawns other threads (e.g. to
listen for network connections) the application will linger indefinitely
because those threads likely never terminate. Those threads are more
correctly called daemon threads: they are background processes that do no
real application work until a request comes in, at which point they should
spawn another thread to handle the request and listen for the next one. In
summary:

- the entry point thread is a user thread;
- the listener thread spawned by the entry point thread is a daemon thread;
and
- the request processor threads spawned by the listener thread are user
threads.

Naturally, if the listener thread is just sitting there doing nothing, you
would like it to shut down when the application shuts down. You can
accomplish this by calling listenerThread.setDaemon(true) before starting
the thread.

Things work slightly differently for GUI applications. The GUI event thread
terminates when all windows are disposed of. To accomplish this, make sure
that every frame has its default close operation set to DISPOSE_ON_CLOSE:

myFrame1.setDefaultCloseOperation(DISPOSE_ON_CLOSE);

You can also set the main frame to exit the application on close:

myMainFrame1.setDefaultCloseOperation(EXIT_ON_CLOSE);

but that has the unfortunately consequence of terminating any user threads
that may still be running and isn't quite as clean.
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"alan jeeves" <fake (AT) fake (DOT) com> wrote

alan jeeves · Guest

thanks for that.

The app is indeed a server like app (how did you know? Smile

and it does wait
for connections from clients.

The app closes clean (enough for me) when I run it on the command line and
press Ctrl+C but within JBuilder (like you've said) it closes the app badly.
Without me changing my code, is there anyway to config jbuilder to close it
in a similar manor as pressing Ctrl+C does?

Thanks
Alan

"Kevin Dean" <NkOdSePaAnM (AT) datadevelopment (DOT) com> wrote

Kevin Dean · Guest

Not that I'm aware of, no. When spawning your background listener thread,
just call setDaemon(true) on the thread before starting it. You will, of
course, have to ensure that there is at least one thread (e.g. a graphical
status monitor) that is non-daemon.

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"alan jeeves" <fake (AT) fake (DOT) com> wrote