> On 16 Jul 2016, at 07:08, John Zhuge <jzh...@cloudera.com> wrote:
>
> Hi all,
>
> What is the guideline to select which Java 8 features to use (e.g., Lambda,
> CompletableFuture, etc.) when developing for both trunk and old branches
> that do not support for Java 8? The goal is to leverage nice Java 8
> features while minimizing backporting effort.
>
> If we plan to use certain Java 8 features, do we recommend any idioms that
> facilitate easy backporting?
>
> Has anybody had experience in RetroLambda
> <https://github.com/orfjackal/retrolambda>?
>
If you are writing code for trunk with no plans to backport, I think you get to
use whatever bits of the language you want. That said: I'd recommend we all
start learning to use the language in tests; it's safer to play there. You can
also do some really fun stuff with closures in tests; something i've done in
Groovy in the past, and with scalatest's eventually() clause. you can do things
like define a probe to retry until it succeeds (or fails fast with some
specific exception).; scalatest eventually() even does exponential backoff.
Things like that deliver tangible improvement to any test which sleep+ waits
for things to happen.
I've also been doing stuff in scala closures related to metrics
-lambda-expressions which get evaluated for building metric values. This makes
it easy to write metrics which are evaluated on demand.
Otherwise:
1. I think we learn to use the various map/apply ops and the ability to add
stuff to traits
2. UGI.doAs looks like a very nice target for a lambda-expression variant,
something like
caller.doAs(() -> fs.delete("tmp"))
That'd be adding better java 8 features to core components, to make it easier
to use downstream.
If you want to target older branches and Java 7, it's best to code against
branch-2 and use that in your patch naming, so that yetus builds against java7.
Locally, I've gone to Java 8 JVMs, but with Java 7 language set.
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