Is there any performance reason to declare method parameters final in Java?

The only benefit to a final parameter is that it can be used in anonymous nested classes. If a parameter is never changed, the compiler will already detect that as part of its normal operation even without the final modifier. It's pretty rare that bugs are caused by a parameter being unexpectedly assigned - if your methods are big enough to need this level of engineering, make them smaller - methods you call can't change your parameters.