Behavior of allMatch, anyMatch and noneMatch for empty Stream

[Remi Forax]

On 12/12/2012 07:10 PM, Peter Levart wrote:
>
> But isn't checking for null going to defeat any possible future 
> optimizations that could optimize the object away?
>

no, the VM tracks if a reference is effectively null or not.

> Peter
>

Rémi

> On Dec 12, 2012 5:51 PM, "Remi Forax" <forax at univ-mlv.fr 
> <mailto:forax at univ-mlv.fr>> wrote:
>
>     On 12/12/2012 03:22 PM, Vitaly Davidovich wrote:
>     > Brian,
>     >
>     > I think NPE should be thrown when predicate is null irrespective
>     of stream
>     > length for consistency sake.
>     >
>     > Thanks
>
>     yes, it this should be true for any parameters that are typed by a
>     functional interface at least in java.util and java.util.stream.
>     We don't want user to send null as a lambda exactly like we don't want
>     user to send a null enum.
>
>     Rémi
>
>     >
>     > Sent from my phone
>     > On Dec 12, 2012 9:16 AM, "Brian Goetz" <brian.goetz at oracle.com
>     <mailto:brian.goetz at oracle.com>> wrote:
>     >
>     >> These values are correct.
>     >>
>     >> All/None match correspond to universal quantification, which can be
>     >> vacuously satisfied; Any match corresponds to existential
>     >> quantification, which cannot.
>     >>
>     >> On 12/12/2012 6:26 AM, elena votchennikova wrote:
>     >>> Hi,
>     >>>
>     >>> please clarify behavior of allMatch(Predicate),
>     anyMatch(Predicate) and
>     >>> noneMatch(Predicate) methods for empty Stream.
>     >>>
>     >>> 1) Please look at the next code:
>     >>> System.out.println(Streams.emptyStream().allMatch(o -> true));
>     >>> System.out.println(Streams.emptyStream().anyMatch(o -> true));
>     >>> System.out.println(Streams.emptyStream().noneMatch(o -> true));
>     >>>
>     >>> The result output will be:
>     >>> true
>     >>> false
>     >>> true
>     >>>
>     >>>
>     >>> Is it OK? And will such behavior be specified?
>     >>>
>     >>> 2) Methods allMatch, anyMatch and noneMatch throw
>     NullPointerException
>     >>> if Predicate is null, for example:
>     >>> Stream notEmptyStream = Arrays.stream(new Object[] {new
>     Object()});
>     >>> notEmptyStream.allMatch(null);
>     >>>
>     >>> But if Stream is empty methods will not throw NPE.
>     >>> So, next code will print same result as in point 1)
>     >>> System.out.println(Streams.emptyStream().allMatch(null));
>     >>> System.out.println(Streams.emptyStream().anyMatch(null));
>     >>> System.out.println(Streams.emptyStream().noneMatch(null));
>     >>>
>     >>> Is it OK or calling these methods with null-Predicate should
>     throws NPE?
>     >>>
>     >>>
>     >>>
>     >>> Best regards,
>     >>> Elena
>     >>>
>     >>
>
>