Stream reuse in superclass (original) (raw)

Jose jgetino at telefonica.net
Thu Apr 4 23:59:18 PDT 2013

Well, the first step in introducing streams in my existing code was to use conversions 

   Collection--> Stream -->Collection

inside the body of existing methods, to take advantage of the stream operations. This step leaded to a significant simplification of many procedures.

Next step was to wonder, do really I need these collections?. Then I found methods in my code that would admit replacing collections with streams in their signature, leading again to a simplification of the code, because it saved many conversions.

This procedure is what I mean for adapting old code to the streams framework. I found it a natural way to experiment with streams, because you already has the code and knows how it is expected to perform.

And it was a smooth path until the case that generated this thread. The rule that I submited to your consideration would correspond to the second step of this path: refactoring method signatures.

-----Mensaje original----- De: David Holmes [mailto:david.holmes at oracle.com] Enviado el: viernes, 05 de abril de 2013 7:30 Para: Jose CC: lambda-dev at openjdk.java.net Asunto: Re: Stream reuse in superclass

On 5/04/2013 3:22 PM, Jose wrote:

So, if I understood you, a rule to adapt old code based on Collections to the new paradigm would be something like:

"try to produce streams instead of collections when possible, but keep on consuming collections"

I'm not sure what that means.

The Stream-based API is a completely different mindset to operating directly on Collections. I'm not sure there is a "rule" to "adapt".

David

-----Mensaje original----- De: David Holmes [mailto:david.holmes at oracle.com] Enviado el: viernes, 05 de abril de 2013 3:31 Para: Jose CC: lambda-dev at openjdk.java.net Asunto: Re: Stream reuse in superclass On 5/04/2013 6:59 AM, Jose wrote: I have a class that contains a method that consumes a Stream (previously was a Collection) And that is your problem. You can not think of operations on a stream the way you would a collection, as a stream is not a collection. Your class that operated on the elements of the collection would now become an operation to be passed to a suitable stream method to be applied to each element. David Class Foo{ bar(Stream s){ ......... } }

This method is overriden in a subclass, that first consumes the stream and then calls super Class PowerFoo extends Foo{ bar(Stream s){ doImportantThingsWidth(s); //now the stream is consumed :-( super.bar(s) } } What is the recomended way to handle situations like this?. Curently I'm collecting the stream into a list and getting two streams from it.

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