I've seen a lot of discussions on NPE versus IAE, and in the end they
all condense down to what Matt stated here: Those who favor NPE cite the
JDK classes as a pattern to follow, and those who favor IAE say it is a
better description of the problem. From my perspective, both are valid
viewpoints, and a project simply needs to choose one. In the end, the
choice is neither "right" nor "wrong" - it is just a choice.
-Adrian
On 8/30/2013 8:07 AM, Matt Benson wrote:
Let me stir the pot:
At a fundamental level I agree that a required *argument* should throw an
IllegalArgumentException when null is supplied. However, ISTR the decision
to do otherwise in [lang] having been discussed on-list in the
not-so-distant past, and the result of that discussion being that NPE is
usually the result in the core JDK classes. So I wouldn't characterize the
situation as "[lang] *just happens* to throw NPE." Now, [lang] is in a
slightly unique situation as its stated mission is to complement Java SE,
so it could be argued that [lang] is under greater pressure to conform for
that reason. But my personal preference, in light of the standing decision
with [lang], would be for consistency throughout Commons components
*despite* the fact that at a purely semantic level I agree with the
arguments in favor of IllegalArgumentException.
To summarize, +1 for NullPointerException from me.
Matt
On Fri, Aug 30, 2013 at 9:36 AM, Benedikt Ritter <brit...@apache.org> wrote:
2013/8/30 sebb <seb...@gmail.com>
On 30 August 2013 15:19, Benedikt Ritter <brit...@apache.org> wrote:
I've removed the generics in r1518974, thanks for spotting that sebb.
Regarding the exception to throw I'm indifferent. The important thing
is
to
fail early.
... and with a helpful message.
I personally thing that NPE should be reserved for signaling that some
code
tried to invoke a method on a null reference.
+1
In our case null is illegal because we know that some code later on
would
break if we accept a null reference. So IllegalStateException makes
sense.
s/IllegalStateException /IllegalArgumentException/
+1
Sorry, I meant IAE of corse.
Imaging having a method that accepts an int and only positive ints are
valid. You would throw an IllegalArgumentException if a negative int is
passed to that method and not a NegativeIntegerException (or what
ever).
But James has a point. If [LANG] uses NPE maybe we should stick to
this.
I don't think we have to do the same as LANG, so long as the Javadoc is
clear.
Feel free to change it. I'll leave it for now since there doesn't seem
to
be consensus?!
Unless there are other reasons than "LANG happens to use NPE" I think
we should stick with IAE, as it more clearly indicates the the problem
is not within the method throwing it.
The problem with using NPE to flag parameter errors is that it
confuses the user as to the likely cause.
Leave NPEs to the runtime system.
agreed.
Benedikt
2013/8/30 James Carman <ja...@carmanconsulting.com>
Well, the problem with using NPE is that we as Java developers have
learned through the years that NPE typically is an "oh crap"
situation, where something is terribly wrong (we hate seeing those).
Thus, our users may have knee-jerk reactions and not even know to
inspect the message for the real cause. IAE is less alarming, IMHO.
Just my $0.02, but we've been doing it that way for a long time in
[lang], so be it.
On Fri, Aug 30, 2013 at 9:01 AM, sebb <seb...@gmail.com> wrote:
AFAIK "accidental" NPEs don't have a message associated with them.
So provided that the assertion generates the NPE with a suitable
message (e.g.as currently done for the IAE) then it *should* be
possible for the end user to distinguish the two cases.
I am slightly in favour of retaining IAE as the cause is obvious
with
needing to look at the NPE message.
==
Horrible hack: - if you want to use NPE, you could wrap an IAE in
the
NPE:
npe = new NPE(msg);
npe.initCause(new IAE(msg));
throw npe;
Or vice-vera, of course!
Not sure that gains anything, but it does make the stack trace look
more impressive!
On 30 August 2013 13:42, James Carman <ja...@carmanconsulting.com>
wrote:
Commons Lang's Validate.notNull() throws NPEs. I don't know that
I've
necessarily agreed with that, but at some point a decision was made
that null constraint violations should throw NPEs. Food for
thought.
On Fri, Aug 30, 2013 at 8:32 AM, Gary Gregory <
garydgreg...@gmail.com>
wrote:
On Fri, Aug 30, 2013 at 8:25 AM, Emmanuel Bourg <
ebo...@apache.org>
wrote:
+ if (parameter == null) {
+ throw new IllegalArgumentException("Parameter '"
+
parameterName + "' must not be null!");
+ }
+ }
+}
Isn't a null value supposed to throw a NPE ?
Not always IMO. When I see an NPE I assume something is very wrong
and
that
it could be a bug in the impl OR a call site, somewhere on the
code
path.
With an IAE, I know for sure it's a problem in the call site
(which
could
be a bug of course).
I does not help that the JRE/JDK is inconsistent, so it's hard to
find
examples.
Gary
Emmanuel Bourg
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