RFR: 8274412: Add a method to Stream API to consume and close the stream without using try-with-resources

[Brian Goetz]

I am not really sure we’ve gotten the right idiom here yet.  I’d like to slow down a bit before making an API decision.  

What id suggest is capturing the proposed api and spec on list, and let’s let this sit and bake for a bit longer.  My sense is that something better may well emerge if we do. 

Sent from my MacBook Wheel

> On Oct 9, 2021, at 5:41 AM, Tagir F.Valeev <tvaleev at openjdk.java.net> wrote:
> 
> On Sun, 3 Oct 2021 11:00:25 GMT, Tagir F. Valeev <tvaleev at openjdk.org> wrote:
> 
>> Currently, when the stream holds a resource, it's necessary to wrap it with try-with-resources. This undermines the compact and fluent style of stream API calls. For example, if we want to get the `List` of files inside the directory and timely close the underlying filehandle, we should use something like this:
>> 
>> 
>> List<Path> paths;
>> try (Stream<Path> stream = Files.list(Path.of("/etc"))) {
>>    paths = stream.toList();
>> }
>> // use paths
>> 
>> 
>> I suggest to add a new default method to Stream interface named `consumeAndClose`, which allows performing terminal stream operation and closing the stream at the same time. It may look like this:
>> 
>> 
>>    default <R> R consumeAndClose(Function<? super Stream<T>, ? extends R> function) {
>>        Objects.requireNonNull(function);
>>        try(this) {
>>            return function.apply(this);
>>        }
>>    }
>> 
>> 
>> Now, it will be possible to get the list of the files in the fluent manner:
>> 
>> 
>> List<Path> list = Files.list(Path.of("/etc")).consumeAndClose(Stream::toList);
> 
> CSR is [posted](https://bugs.openjdk.java.net/browse/JDK-8274994), please review!
> 
> -------------
> 
> PR: https://git.openjdk.java.net/jdk/pull/5796