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.
--Scott E. Hudson and Ian Smith
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