Am 2014-05-06 15:27, schrieb Benedikt Ritter:
Hi Thiago,
2014-05-06 14:53 GMT+02:00 Thiago Andrade <thia...@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.
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?
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/NullPointerException.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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