RFR(m): 8140281 deprecate Optional.get()

[Alan Bateman]

On 29/04/2016 10:23, Andrej Golovnin wrote:
> :
>
> "There are many Java 8 developers using streams() and optionals
> with an imperative programming mindset still."
>
> And here is an example from JDK. Take look at the code
> http://cr.openjdk.java.net/~smarks/reviews/8140281/webrev.0.jdk/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/JlinkTask.java-.html
> :
>
>   397         cf.modules().forEach(m -> {
>   398             ModuleReference mref = m.reference();
>   399             map.put(mref.descriptor().name(), mref);
>   400         });
>   401
>   402         // set of modules that are observable
>   403         Set<ModuleReference> mrefs = new HashSet<>(map.values());
>   404
>   405         // add the other modules
>   406         for (String mod : otherMods) {
>   407             Optional<ModuleReference> omref = finder.find(mod);
>   408             if (omref.isPresent()) {
>   409                 ModuleReference mref = omref.get();
>   410                 map.putIfAbsent(mod, mref);
>   411                 mrefs.add(mref);
>   412             } else {
>   413                 // no need to fail
>   414             }
>   415         }
>
> It is a mix of imperative and functional programming.
> But you can rewrite it in a more functional style.
> The lines 397-400 can be rewritten as:
>
>        cf.modules()
>           .stream()
>           .map(ResolvedModule::reference)
>           .forEach(mref -> map.put(mref.descriptor().name(), mref));
>
>
which btw is exactly how it is implemented elsewhere. However it was not 
possible to write it this way before refactoring of the API a few weeks 
ago and it's just that the jlink code wasn't cleaned up much during the 
refactoring.

In general then we have lots of code in the JDK that could be refactored 
and cleaned up. Some of the new code (such as jlink) has had to go 
through many iterations and refactoring and very easy to end up with 
mixes of functional and imperative. I expect there will be a lot of 
churn in this code over the coming months (not features work and just 
improving and iterating on the current implementation) and hopefully in 
better shape then.

-Alan.