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From "Bill Barker" <>
Subject Re: [Math] Usage of "NullPointerException"
Date Thu, 05 Aug 2010 01:23:08 GMT

From: "Gilles Sadowski" <>
Sent: Wednesday, August 04, 2010 2:27 PM
To: <>
Subject: Re: [Math] Usage of "NullPointerException"

>> > A simpler policy would be to not check for "null" and let the JVM do 
>> > it. As
>> > the JVM will do it anyway, it's a redundant check when the reference is 
>> > not
>> > null, i.e. most of time (in legitimate usage).
>> This simpler policy seems fine to me.
>> However, it is an important change from previous behaviour.
> In practice it is not that important: there are currently only 29
> occurrences of messages referring to "null"; among those only 6 raise a
> NullPointerException (the others throw an IllegalArgumentException).
>> > When the usage is wrong, the error is obvious and always the same 
>> > ("null
>> > reference") and the "NullPointerException" fully identify the problem. 
>> > I
>> > don't see why we should have a localized version of it. Yes, again, 
>> > there
>> > are detailed messages saying:
>> >  "the covariance matrix cannot be null"
>> >  "the function cannot be null"
>> >  "the denominator cannot be null"
>> >  etc.
>> > But since any reference can potentially be "null", do you really intend 
>> > to
>> > have a specific meesage for every object?
>> For these very low level errors, I would be happy with the single
>> message from JVM.

I would be happy with a single message from the JVM.  Especially since we 
are now inconsistent about when we use the localized version vs. the JVM 
version of NPE.

> So, shall I remove all checks for "null" (and those items in
> "LocalizedFormats" that are used for reporting it)?
> Should I open a JIRA issue?
It looks like we'll need a JIRA for this.  Since we have places that 
document that it throws IAE on a null parameter, that would be an 
incompatible change for 2.2.  So they would have to wait for 3.0.

If you want to change the places where we throw a localized NPE, that would 
be fine for 2.2 IMHO (my quick spot check only shows BigFraction).  Knock 
yourself out.

> Gilles
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