NotYetImplementedError [Was: NYIException]

[Etienne Gagnon]

Hi all,

I personally think that a Java application should not try to discover 
the JVM/library version through an akward usage of exceptions/errors.

If an application wants to adapt to some version of the above, it should 
use System.getProperty() and test for a specific jvm/class-library 
version.  If an application fails to do so, and if this application 
calls an unimplemented method, I think that the best course of action is 
for an error to be thrown, so that execution fails with a beautiful 
stack trace, informing the application developer of the problem.

So, my proposal is:
(1) Throw NotYetImplementedError extends Error (or LinkageError?)
(2) Document clearly that users of Classpath SHOULD NOT catch this 
exception, but use System.getProperty("gnu.classpath.version") instead.
(3) Document, in the VM interface, that such property should be set, of 
course.

Etienne


David Holmes wrote:
> Per Bothner wrote:
>
> > The latter is true, but the former does not follow.  I
> > think creating
> > a new non-portable sub-class is solving a non-existent problem.
>
>
> Ah I see where you are coming from. If an application wants to run
> under a variety of VM's and also wants to deal with Classpath's
> limitations, it is not going to be able to compile against a host VM
> that doesn't have this Classpath specific exception type. If the
> application uses the RuntimeException type in its catch clause then it
> will catch genuine RuntimeExceptions too and will have to try and
> distinguish them (which means reflectively querying its type for the
> Classpath specific exception type).
>
> Using any existing exception type that could never normally be thrown
> by these methods when they are implemented, solves this problem. And
> UnsupportedOperationException is as semantically close as you'll get
> to the right kind of exception.
>
> Note that an optional method that is not yet implemented (how could
> you tell? :) ) should always throw UnsupportedOperationException, not
> NYIException.
>
> David Holmes
>
>
>
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--
Etienne M. Gagnon, Ph.D.             http://www.info.uqam.ca/~egagnon/
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