Interesting you approach FP with Java examples, functional language examples would have come handy too (can be cleaner of Java lib calls).
I know a bit of Scala and sure the code it's cleaner and there is a lot of awesome resource that JAVA doesn't have, but I learn functional in a project that 'require JAVA' because the client force that decision and there is so many projects that have to use this language for some reasons so we find VAVR and I think is good to show this can of alternatives.
I see your case, and it makes sense. VAVR creators specifically say they offer data structurures, not all for functional purity (eg IO monads): github.com/vavr-io/vavr/issues/20#.... If I was on Java path, I'd say I use some of elements of fucntional programming, but not the full stack.
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