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From Paulex Yang <paulex.y...@gmail.com>
Subject Re: NullPointerException
Date Mon, 20 Mar 2006 08:41:28 GMT
Chris Gray wrote:
> On Friday 17 March 2006 08:47, Anton Avtamonov wrote:
>
>   
>> Actually null-processing and corresponding NPEs are very very often
>> omitted from the spec.
>> I would say that according to the guidelines Paulex proposed (and as I
>> understood we agreed on) we should be RI-compatible in this case.
>> Really, spec doesn't say anything regarding null-processing and
>> therefore throwing NPE in this case does *not* contradict to the spec.
>> Having NPE we will be better RI-compatible and stay on the same
>> position in the spec-compatibility (since it is silent).
>> Therefore I suggest to be RI-compatible by default in all cases when
>> spec keep silence. I believe it well suites Paulex guidelines (please
>> correct me if I wrong).
>>     
>
> +1
>
>   
>> Talking about how particulary we should throw NPE I'm not sure what to
>> advise: in many cases RI just produces them automatically when actual
>> call like null.someMehtod() occurs. To provide better notation we can
>> do that directly, i.e.
>> if (someVar == null) {
>>     throw NullPointerException("some valuable message")
>> }
>> I'm not really sure what is better and would like to know what others
>> think about.
>>     
>
> I prefer to let these things happen automatically whenever possible. 
> Introducing an explicit check adds extra bytecodes and probably extra CPU 
> cycles in the non-null case. On some VMs null.someMethod() might be slower in 
> the null case, but if the RI also throws NPE then these cases should be truly 
> exceptional in the sense that they indicate a programming error or a missing 
> resource. OTOH if the RI treats a null argument as a normal case then this 
> should be implemented using 'if (someVar == null)', not by catching a NPE(!).
>   
My opinion is:
either is fine, the only principle is the exception order must be 
compliant with RI, if it can be happen automatically, great. if can not, 
then the explicit check is necessary, while the performance should be 
the second consideration.
> Chris
>
>   
>> Btw, when we will work on documentation (javadoc) I think we should
>> append references to the standard Sun API in the methods javadoc with
>> the direct info about null-processing and NPE if a method can produce
>> it (when it is missing from the original spec of course).
>>
>> --
>> Anton Avtamonov,
>> Intel Middleware Products Division
>>     
>
>   


-- 
Paulex Yang
China Software Development Lab
IBM



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