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From "Kish, Robert" <>
Subject RE: [lang]
Date Tue, 13 May 2014 19:17:24 GMT
What I haven't seen anyone mention yet is my point of view as a user. I
don't mind getting back NPE - I just want an error message in the
exception when that happens. If I get back null as the text, then that
usually tells me the error is a JVM one or an unexpected one in the
library I'm using. When I get back an exception message or an IAE, then
I know it's something I did.

What I don't want to see happen is throwing NPE with no text, in place
of IAE. That's the case where a user of the library might be confused as
to the cause of the exception.

-----Original Message-----
From: Roger Whitcomb [] 
Sent: Tuesday, May 13, 2014 02:16 PM
To: Commons Developers List
Subject: RE: [lang]

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 []
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.


On May 6, 2014, at 2:54 PM, Paul Benedict <> 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 <>
>> On 6 May 2014 22:27, "Michael Osipov" <> wrote:
>>> Am 2014-05-06 15:27, schrieb Benedikt Ritter:
>>>> Hi Thiago,
>>>> 2014-05-06 14:53 GMT+02:00 Thiago Andrade <>:
>>>>> Hello people,
>>>>> Analizing the JIRA issue
>>>>> 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
>>>> 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.
>> on.html
>>> 2.
>> "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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