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From Tim Ellison <t.p.elli...@gmail.com>
Subject Re: NullPointerException
Date Fri, 17 Mar 2006 09:08:04 GMT
Anton Avtamonov wrote:
> On 3/17/06, Karan Malhi <karan.malhi@gmail.com> wrote:
>> Hi,
>> Some of the methods/constructors in the API throw a NullPointerException
>> when a null is passed in as an argument. The spec doesnt say anything that
>> the method/constructor should throw a NullPointerException, neither does it
>> say anything about how the method/constructor should behave when a null is
>> passed in.
>> What should be the approach in that case?
>> 1. Could we check for null within a method and handle it so that the method
>> does not unneccessarily throw an NPE (this would differ from how the spec
>> would behave) or
>> 2. should we allow the method to throw an NPE if the spec method also throws
>> it?
> Hi,
> 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).

I agree.

> 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 think either is fine.  We have tended to let NPE be thrown 'naturally'
and only tested for it if we need to get the order of exceptions right
wrt the RI.

> 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


Tim Ellison (t.p.ellison@gmail.com)
IBM Java technology centre, UK.

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