RFR 9: 8138963 : java.lang.Objects new method to default to non-null
Roger.Riggs at Oracle.com
Thu Oct 8 21:42:29 UTC 2015
Thanks for the insight, I hope it will help cut down on the thrashing.
Isn't there a 4th form that throws missing?
There was quite a bit of support for a version the never returned null
and threw an exception if the replacement was null.
On 10/8/2015 5:26 PM, John Rose wrote:
> On Oct 8, 2015, at 12:34 PM, forax at univ-mlv.fr
> <mailto:forax at univ-mlv.fr> wrote:
>> Anyway, in this case the problem is not just overloading, it is the
>> mix of overloading and type inference as you said.
> Add type erasure to this cocktail, and it's perfect.
> My antennae go up when the erased types overlap. When they do,
> there's usually a sad story (with puzzlers) waiting to appear.
> On 7 October 2015 at 23:24, Roger Riggs <Roger.Riggs at oracle.com
> <mailto:Roger.Riggs at oracle.com>> wrote:
>> Please consider and comment:
>> <T> T nonNullOf(T obj, T defaultObj);
>> <T> T nonNullOf(T, obj, Supplier<T> defaultSupplier);
>> Details are in the updated webrev:
> In this case, the erased types are Object(Object, Object) and
> Object(Object, Supplier).
> So the source language (usually) makes all needed distinctions, but
> the bytecodes are full of ambiguity. And nulls are wonderful carriers
> of ambiguity, at both source and bytecode levels.
> Please align this API point with the closely analogous points already
> found in java.util.Optional. In particular, a third throwing form
> looks right.
> Those are my substantive comments.
> Now for bikeshed comments.
> I don't like "Of" here, which doesn't appear in Optional, and seems to
> be used more frequently for factory methods.
> I suggest using Optional::orElse* method names, but kill leading noise
> word "or". "Non-null else foo" is good programmer talk for "non-null
> or else foo". (Speculation: The "or" is present in Optional mainly
> to avoid reserved word "else".)
> - nonNullElse(T,T) (cf. Optional::orElse)
> - nonNullElseGet(T,Supplier<T>) (cf. Optional::orElseGet)
> - nonNullElseThrow(T,Supplier<X>) (cf. Optional::orElseThrow)
> — John
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