It is our basic belief that extreme caution is warranted when
designing and building multi-threaded applications,
particularly those which have a GUI component. Use of
threads can be very deceptive. In many cases they appear to
greatly simplify programming by allowing design in terms of
simple autonomous entities focused on a single task. In fact in
some cases they do simplify design and coding. However, in
almost all cases they also make debugging, testing, and
maintenance vastly more difficult and sometimes impossible.
Neither the training, experience, or actual practices of most
programmers, nor the tools we have to help us, are designed
to cope with the non-determinism. For example, thorough
testing (which is always difficult) becomes nearly impossible
when bugs are timing dependent. This is particularly true in
Java where one program can run on many different types of
machines and OS platforms, and where each program must
work under both preemptive or non-preemptive scheduling.
As a result of these inherent difficulties, we urge you to think
twice about using threads in cases where they are not
absolutely necessary. However, in some cases threads are
necessary (or are imposed by other software packages) and
so subArctic provides a thread-safe access mechanism. This
section describes this mechanism and how to use it to safely
manipulate the interactor tree from an independent thread.
It is interesting to consider this strategy in the light of experience gained from occam. Whilst occam totally lacks the carefully designed library support of the JFC and the JDK, it does in principle allow straightforward multi-threaded GUI programming. Coping with non-determinism is a normal part of the occam design process, not the insurmountable issue faced by users of the JFC.
Perhaps a sensible approach is to use JavaPP channels to dissociate
Swing GUIs from the underlying core application.
Richard Beton B.Sc. C.Phys. M.Inst.P.
Roke Manor Research Limited
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Java: In a world without Fences, who needs Gates?