Hi Bruce,
Functional programming techniques will improve any kind of programming by making programs safer and easier to
test and to reuse. This said, it might not help so much when interacting with libraries that are not functional themselves. In such case, one has to wrap the non functional library into a functional wrapper. For example, if a library throws exceptions as a mean to communicate about exceptional conditions, you have to translate these exceptions into a functional representation.
Another problem is that functional IO is one of the trickiest part of functional programming in Java because Java lack the necessary elements for this, so you have to develop you own IO functional library. Programs that are constantly performing IO over time are the most difficult to make functional, and it might not be worth it. But only you can decide, and for this, you have to learn how to do it!
To summarize, probably not all functional techniques will be beneficial in your case. But the main problem is that it is practically impossible to evaluate the benefits without understanding how it works. So you have to check for yourself. What I would suggest is reading the first chapter (available as a free download), and see if looks promising.
