Replace RowOperation.initialValue() and rowAggregator() by collect(Collector)

[Douglas Surber]

Correct. Per the JavaDoc, the default value for rowAggregator is (p,r) -> null.

Douglas 
> On Oct 25, 2017, at 8:47 AM, Lukas Eder <lukas.eder at gmail.com> wrote:
> 
> But what is submit supposed to do when there is no collect() call (or in the current API, no initialValue() call)? The only reasonable types to return from submit() and then toCompletableFuture() would be Void or ?, no? What am I missing?
> 
> 2017-10-25 18:43 GMT+03:00 Douglas Surber <douglas.surber at oracle.com <mailto:douglas.surber at oracle.com>>:
> 
>> On Oct 25, 2017, at 8:40 AM, Lukas Eder <lukas.eder at gmail.com <mailto:lukas.eder at gmail.com>> wrote:
>> 
>> In my suggestion, I assumed that OperationGroup.rowOperation could return a RowOperation<?>, and only calling the RowOperation.collect() method would make the type parameter more concrete, thus collect() would have to be a generic method. All the other methods on RowOperation currently do not rely on its type parameter.
>> 
> 
> submit does and by transitivity toCompletableFuture, which is where the real problems show up.
> 
> Douglas
>