Revisiting MayHoldCloseableResource

[Brian Goetz]

>> Observation: the need for Stream to have a close() method comes about
>> because of the desire to have static factory methods that will create
>> streams that encapsulate a resource that requires closing, when there is
>> no way to get access to that underlying resource.  Such as Files.walk(dir)
>> or Files.lines(path).
>> 
> 
> Or rather, no way provided in JDK. What if these methods were
> recast do so? That is, exposing some closeable thing.
> Maybe something like Files.directoryStream(dir).files().
> 
> A little less convenient, but avoids lots of problems.

This was my thinking at first too, but don't forget about cases like flatMap, where the stream is created inside a pipeline.  Let's say we do as you suggest for dirStream.  But what if you want "all the lines in all those files"?  You'd flatMap them to a stream of strings: 

try (dirStream = ...) {
  dirStream.stream()
                    .flatMap(path -> Files.lines(path))
                    ...
}

There's no place to put TWR around the lines() stream creation even if you expand it as you suggest.  

This (reasonable!) use case makes me hesitant to solve the problem simply by pretending it didn't occur to us to provide static methods here.