Re: NotYetImplementedError [Was: NYIException]

[Etienne Gagnon]

David Holmes wrote:
> I'm not so sure this is about actual version information but more
> about not yet implemented methods in a VM/library that purports to
> support the version of the API that includes that method. Classpath is
> in the unfortunate state of supporting different versions of API's
> depending on which class you are looking at, so what version
> information would the system property return?

It should report Classpath's version (e.g. 0.06).

I do really think that an application should not use the exception 
mechanism to discover the class library version (of course, classpath 
0.06 != specific sun jdk version, but this is still a version).

Throwing a error seems to be the right thing to do.

Many applications (including SableCC, I think) do things like:

try ...
catch(Exception e)
{...}

In such context, a missing method is definitely *not* an exception.

If a programmer knows that his application will be running on an 
incomplete/inconsistent class library, he should definitely use a system 
property to make the appropriate control-flow choices.  In the *worst* 
ugly hack case, he could do a catch(NotYetImplementedError e), but this 
should definitely be avoided.

Throwing an error and aborting the application is the right thing to do 
for 99,9% of Java applications.  If an application was coded expecting 
some method to be present, then an error should happen.  This is already 
the case with Sun's JDK, e.g.:

An application is written for JDK 1.4.  Application is run on JDK 1.1. 
A 1.4-specific method is called  =>  LinkageError is thrown.


Etienne

--
Etienne M. Gagnon, Ph.D.             http://www.info.uqam.ca/~egagnon/
SableVM:                                       http://www.sablevm.org/
SableCC:                                       http://www.sablecc.org/