Hello David,
testing the gatherer api, I also wanted a "window" operation as the one you are
describing.
My use cases is a text file with some sections containing items organized like
this
:section1
item1
item2
item3
:section2
item1
item2
...
For me the signature of such method, windowGroupBy??, should take a Predicate
(is a section, so the reverse of what you are suggesting) and a function that
take a value (for which the predicate is true) and return a Collector,
so I can write something like
record Section(String name, List<String> items) {}
String input = ...
List<Section> sections = input.lines()
.gather(Gatherers.windowGroupBy(line -> line.startsWith(":"), name ->
Collectors. collectingAndThen (Collectors.toList(), list -> new
Section(name.substring(1), list))))
.toList();
regards,
Rémi
> From: "David Alayachew" <[email protected]>
> To: "core-libs-dev" <[email protected]>
> Sent: Wednesday, January 10, 2024 7:19:26 AM
> Subject: Re: Gatherers -- conditionalWindowFixed?
> And this may also be better named as a split method instead of the long
> conditionalWindowFixed.
> On Wed, Jan 10, 2024 at 1:17 AM David Alayachew < [
> mailto:[email protected] | [email protected] ] > wrote:
>> Oh, I made a mistake. Let me try it again.
>> If the predicate is true, add the element to the current list (create list
>> prior
>> if needed). Else if the predicate is false, send the list down to the stream,
>> then add the element to a new list (the new current list, if you will).
>> On Wed, Jan 10, 2024 at 1:05 AM David Alayachew < [
>> mailto:[email protected] | [email protected] ] > wrote:
>>> Hello Core Libs Dev Team,
>>> I have been reading through JEP 461 ( [ https://openjdk.org/jeps/461 |
>>> https://openjdk.org/jeps/461 ] ) about Gatherers, and I'm really excited for
>>> what this will enable for us.
>>> By far, the most important functionality that this API facilitates is the
>>> ability to create windows. Anytime I needed a window, I was basically
>>> forced to
>>> use a for loop. Now, the 2 most common window cases are being handed to us
>>> for
>>> free. It is very much appreciated.
>>> Could we add one more method for a conditionalWindowFixed? We would need to
>>> pass
>>> in some Predicate<T>. If the predicate returns true, create a list (if it
>>> does
>>> not already exist) then add the element to it. If the predicate returns
>>> false
>>> while the list is empty, then just move along to the next. Else if the
>>> predicate returns false while the list is non empty, pass the list down into
>>> the stream. So, you end up with Stream<T> -----> Stream<List<T>>.
>>> The reason I think this is worth adding is because it facilitates a really
>>> common use case. We may not want all windows to be the same size.
>>> Is this something worth adding to the Gatherers API?
>>> Thank you for your time and help!
>>> David Alayachew
