[PATCH] 8178117: Add public state constructors for Int/Long/DoubleSummaryStatistics

[Chris Dennis]

Hi Paul (et al)

Like all things API there are wrinkles here when it comes to implementing.

This patch isn’t final, there appears to be no existing test coverage for these classes beyond testing the compensating summation used in the double implementation, and I left off adding any until it was decided how much parameter validation we want (since that’s the only testing that can really occur here).

The wrinkles relate to the issues around instances that have suffered overflow in count and/or sum which the existing implementation doesn’t defend against:

 * I chose to ignore all parameters if 'count == 0’ and just leave the instance empty. I held off from validating min, max and count however. This obviously 'breaks things’ (beyond how broken they would already be) if count == 0 only due to overflow.
 * I chose to fail if count is negative.
 * I chose to enforce that max and min are logically consistent with count and sum, this can break the moment either one of the overflows as well (I’m also pretty sure that the FPU logic is going to suffer here too - there might be some magic I can do with a pessimistic bit of rounding on the FPU multiplication result).

I intentionally went with the most aggressive parameter validation here to establish one end of what could be implemented.  There are arguments for this and also arguments for the other extreme (no validation at all).  Personally I’m in favor of the current version where the creation will fail if the inputs are only possible through overflow (modulo fixing the FPU precision issues above) even though it’s at odds with approach of the existing implementation.

Would appreciate thoughts/feedback.  Thanks.

Chris


P.S. I presume tests would be required for the parameter checking (once it is finalized)?