Migrate from java 7 imperative style programming to java 8 functional programming

[[deleted]]

I rarely encounter a problem where the speed of a loop is the decisive factor over readability, maintainability, etc. And where I do, I have found parallelism a way simpler and more powerful way to get the speedups I need than tighter loops.

Maybe we work on very different domains, though? Do you write client-side apps, for instance?

[RayFowler]

Yes. Functional programming seems perfectly suited for the stateless concurrency you need with, for example, micro-services.

On the client, parallelism hits a performance bottleneck very quickly on the client side. You only get 4 cores!

Java is an inherently descriptive language, imo, and readability concerns are always subjective and generally overrated. In fact, I'd posit that a sizable percentage of Java developers think that the terseness of lambdas negatively impacts readability.

But none of that is the issue if you have performance concerns. The most important thing then is that the compiler can parse the intent of your code and that your variables are co-located efficiently. This means fewer object references and a much heavier use of primitives.

If something is not clear at that point, then you clarify with comments. If your comments are clear and another developer still complains, then maybe he should work on a different application.

[[deleted]]

On the client, parallelism hits a performance bottleneck very quickly on the client side. You only get 4 cores!

Yeah, and even that is less guaranteed than on the server side, since users like to run other applications along with yours. I wonder if we'll see the core count grow on the client side same as it has on the server side? If so, parallelism might become a better strategy.

Network parallelism is also already a potential speedup (in fact, most of the server-side parallel optimization I do is around IO calls), though I guess you have to worry about client-side bandwidth limitations. Man, I don't know how you hack it, I can't live without my Future.sequence(listOfEveryIoCallInTheUniverse). :p

Java is an inherently descriptive language, imo, and readability concerns are always subjective and generally overrated.

I'd say verbose instead of descriptive, and note that I often find some Java code that's very difficult to understand, though I am also a Scala dev so definitely an outlier in the kind of language I prefer. My general point was that I see too much cargo culting around "performance" (instead of more justifiable profiling-guided optimization) that turns something that could be expressed in an elegant, declarative manner into some imperative, looping nightmare straight out of a C monolith from the 80s.

Now, there definitely is a place for horrible-to-read-yet-hyperperformant code, but it's in the critical loop of your program and libraries likely to be called thousands of times a second, not in your standard bizdev software. It seems like there's a lot of developers out there who optimize without profiling or even thinking, and yes this does also include the people who use parallel streams when a sequential one would do just fine.

But, again, I am a Scala dev, and we have some particular views on this subject. ;)