dl at cs.oswego.edu
Sun Sep 23 06:58:31 PDT 2012
On 09/23/12 09:54, Tim Peierls wrote:
> People shouldn't be mapping to null in the first place, any more than they
> should be mapping to NaN.
Yes. (This has been my stance for about 25 years straight :-)
> But the issues make it impossible to write some generic
> Map utilities because the need to recheck forces non-atomicity.
> For findAny etc, the issue is even harder:
> if (!...findAny(...).isPresent())
> // somehow recheck?
> And the need for recheck is even less obvious.
> So unobvious that I still don't see it. As long as you aren't treating null as
> an acceptable value in Streams or as the contents of an Optional, why do you
> need to re-check?
Suppose there are two elements that match predicate, one null, one
nonnull. And suppose the findAny implementation finds the null one
first and so reports an absent Optional.
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