Re: invokeLater and weird race conditions in my swing app

Knute Johnson <>
Fri, 07 Sep 2007 11:40:12 -0700
<hWgEi.420012$wG2.270033@newsfe17.lga> wrote:


I have a swing app that needs to read from a database when building
some of its dialog windows and when updating rows in its JTable
components. My app seems to be suffering from race conditions.
Apparantly randomly it hangs when updating a data model for my JTable.
I have a trace stmt before and after the call to mode.insertRow. The
first trace gets executed, the second does not.

I have discussed this with a colleague who suggest that I use the
function invokeLater to send any swing work to the swing event
dispatching thread. I will look into this but I am puzzled. My app
does not start such a thread explicitly so I wonder how it does get
started. Also, why dont the swing functions do this work anyway? I am
an ex-Motif programmer and from my Motif days I remember that all the
Motif and X11 calls do not render directly - they write a message to
the X11 server which will do the rendering upon rcpt of the message. I
assumed that swing would have a similar design but done using threads
within the app (my main thread making the swing call which would send
the request to the swing event message processing thread). So I
suppose it doesnt work like that then.

Since some of the work my app is doing is database-related this bit
can be slow so maybe this is why things get into a mess. Can any swing
gurus comment on this please?


Andrew Marlow

There is no telling what will happen if one calls Swing GUI methods
outside of the EDT. Blocking the EDT with time consuming tasks will
cause odd things to happen as well. None of the methods of JTable are
marked as thread safe so they must all be called from the EDT.

If you clear up all of the above and are still having hang problems you
might try writing a simple test program to see if you can duplicate the
problem. It is always possible that you found some weird bug but not
likely :-).


Knute Johnson
email s/nospam/knute/

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