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From Gary Gregory <garydgreg...@gmail.com>
Subject Re: [lang]
Date Tue, 13 May 2014 22:46:04 GMT
+1

Gary

<div>-------- Original message --------</div><div>From: Oliver Heger <oliver.heger@oliver-heger.de>
</div><div>Date:05/13/2014  15:33  (GMT-05:00) </div><div>To: Commons
Developers List <dev@commons.apache.org> </div><div>Subject: Re: [lang]
</div><div>
</div>I remembered this discussion just today at work when I was faced with
the following situation: a method is passed parameters which must not be
null and must otherwise be compliant to some validity rules.

So what would authorities recommend: Throw NPE in case of a null
argument and IAE in case of other contract violations? This seems
confusing to me. Therefore, I am in favor of IAE.

Oliver

Am 13.05.2014 20:15, schrieb Roger Whitcomb:
> Just wanted to mention that the Apache Pivot project (Java GUI framework) uses IAE for
most/all cases of null or invalid input arguments (that is, cases where we check the input
arguments), reserving NPE for basically the JVM to throw.
> 
> ~Roger Whitcomb
> 
> -----Original Message-----
> From: Ralph Goers [mailto:ralph.goers@dslextreme.com] 
> Sent: Wednesday, May 07, 2014 9:25 PM
> To: Commons Developers List
> Subject: Re: [lang]
> 
> I have to say that if you look at the JDK for examples of how to code Java correctly
you will be disappointed.  There are lots and lots of classes that are really bad.
> 
> Ralph
> 
> 
> On May 6, 2014, at 2:54 PM, Paul Benedict <pbenedict@apache.org> wrote:
> 
>> This is not a matter of law. If Oracle/Sun set a direction on how to 
>> use NPE, it's a really good idea to follow them -- even if you don't 
>> agree, do it for the sake of consistency. I don't think using IAE is somehow "better"
>> Java than what they are doing. And I give weight to what Joshua said 
>> because he's a former architect of that company. Lang3 was designed to 
>> throw NPE on invalid null arguments because that's what the gurus, 
>> like he, in our industry who publish "best practices" say it should. 
>> If your opinion bears greater weight than those set forth the best 
>> practices, then you win, but I don't advocate going back to IAE for nulls for the
reasons stated.
>>
>>
>>
>>
>> Cheers,
>> Paul
>>
>>
>> On Tue, May 6, 2014 at 4:40 PM, Duncan Jones <duncan@wortharead.com> wrote:
>>
>>> On 6 May 2014 22:27, "Michael Osipov" <1983-01-06@gmx.net> wrote:
>>>>
>>>> Am 2014-05-06 15:27, schrieb Benedikt Ritter:
>>>>
>>>>> Hi Thiago,
>>>>>
>>>>>
>>>>> 2014-05-06 14:53 GMT+02:00 Thiago Andrade <thiagoh@gmail.com>:
>>>>>
>>>>>> Hello people,
>>>>>>
>>>>>> Analizing the JIRA issue
>>> https://issues.apache.org/jira/browse/LANG-1008the
>>>>>> contributors noticed that NumberUtils.max/min methods all have the

>>>>>> same
>>>>>> problem:
>>>>>> They all throw an IllegalArgumentException when according to the
>>> official
>>>>>> documentation (Oracle|Sun) says that a NullPointerException must

>>>>>> be
>>> thrown
>>>>>> when an argument must not be null.
>>>>>>
>>>>>
>>>>> This is not a problem imho. It is a question of API design. I don't 
>>>>> now
>>> an
>>>>> offical documentation that say when IAE or NPE _must_ be thrown.
>>> Sun/Oracle
>>>>> at some point decided to throw NPE when ever a null reference is 
>>>>> passed
>>> to
>>>>> a method that doesn't accept null inputs. I don't feel this is 
>>>>> right,
>>> since
>>>>> a null input is also an illegal argument. Why make a differenciation?
>>> IMHO
>>>>> NPE should be reserved to the JVM, when a method is called on a 
>>>>> null reference, but that's just my opinion.
>>>>
>>>>
>>>> It *is* a problem because NullPointerException and
>>> IllegalArgumentException have concrete semantics layed out in the 
>>> JDK's Javadocs. If you see how both are used in the JDK, you see that 
>>> NPE and IAE are used properly and there is no such restriction to the 
>>> JDK only. If you aread Effective Java, you'll see that you *have to* 
>>> use NPE if a null argument is passed. One might remember the 
>>> NullArgumentException back in Lang 2, it was removed because it is imperative
to use NPE instead.
>>>
>>> Effective Java is a great book, but don't confuse Joshua's advice with law.
>>>
>>>>
>>>> Moreover, the Lang 3 package includes a great class, Validate, which 
>>>> does
>>> things right and now I can ask, why the hell is that not used 
>>> throughout the entire library?
>>>
>>> +1 to this. We should update all of lang to use Validate once we've 
>>> +nailed
>>> this issue.
>>>
>>> Duncan
>>>
>>>>
>>>>
>>>>>> However according to Apache Commons Lang Developer Guide, these 
>>>>>> methods
>>> are
>>>>>> all correct. This guide says that "When throwing an exception to
>>> indicate a
>>>>>> bad argument, always try to throw IllegalArgumentException, even

>>>>>> if the argument was null. Do not throw NullPointerException.".
>>>>
>>>>
>>>> Correct to the dev guide only -- not Java.
>>>>
>>>>
>>>>> Since [lang] is currently designed this way, I'd rather deal with 
>>>>> this issue for 4.0. We can then revisit our initial decision to 
>>>>> only throw
>>> IAE
>>>>> an maybe align it to what the JDK now does. If you want to file an
>>> issue,
>>>>> my opinion is, that it should be fix version 4.0. Changing the
>>> exceptions
>>>>> that are thrown now may break clients (although I think there are 
>>>>> very
>>> few
>>>>> use cases where one should catch IAE or NPE).
>>>>
>>>>
>>>> 4.0 has to use Validate throughout the entire package. NPE and IAE
>>> indicate a programming error in the client not adhering to the 
>>> contract depicted by the Javadocs, so it is the client's problem to deal with
them.
>>> With proper programming, you should not have to catch those exception 
>>> at all.
>>>>
>>>>
>>>>>> This mail was sent in order to discuss around and make decisions

>>>>>> to
>>> solve
>>>>>> this dilemma where the Java official specification says X and the
>>> Apache
>>>>>> official specification says Y.
>>>>>>
>>>>>
>>>>> Can you please provide a lnk to the official specification you're
>>> refering
>>>>> to? ;-)
>>>>
>>>>
>>>> Read Effective Java on exceptions. Thiago provided a URL in the JIRA
>>> issue.
>>>>
>>>> Further good resources:
>>>>
>>>> 1.
>>>
>>> http://docs.oracle.com/javase/7/docs/api/java/lang/NullPointerExcepti
>>> on.html
>>>> 2.
>>> http://docs.oracle.com/javase/tutorial/essential/exceptions/runtime.html:
>>> "One case where it is common practice to throw a RuntimeException is 
>>> when the user calls a method incorrectly. For example, a method can 
>>> check if one of its arguments is incorrectly null. If an argument is 
>>> null, the method might throw a NullPointerException, which is an unchecked exception."
>>>>
>>>> Michael
>>>>
>>>>
>>>>
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>>>>
>>>
> 
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