G'day. Upon seeing some recent emails from this group expressing a somewhat philosophical tone about how the evolving landscape of paradigms in software development may be putting a strain on Java, I just wish to put some comments that others might find interesting down about how a specific Java feature, namely checked exceptions, can be improved so that again, Java perhaps can show how to do something well enough that other languages might try and copy it.
I say the following. Have an abstract checked exception class in the Java SE API. Call it, say, CheckedException. Descendents of this class behave like any other checked exception, with perhaps a few caveats explained in this email. The build script of a deployable artifact (an application or library, but in this case, probably a library explains the situation more clearly) somehow indicates that this deployable artifact (hereon referred to as a library) can declare that descendents of CheckedExceptions (never the CheckedException class itself) are: 1. thrown: A more specific descendent of a checked exception under this clause occurs in the throws clause of a method that is exposed to libraries that are dependent on this one. 2. caught: A more specific descendent of a checked exception under this clause occurs in the catch block of a method that calls a method from a library on which this one depends. 3. ignored: Neither of the above scenarios occurs. *However, methods in this library that call methods that throw a descendent of a checked exception under this clause do not themselves explicitly declare that they throw or catch and deal with the given checked exception*. If a library declares that it throws or ignores a descendent of a CheckedException, in its build script or other deployment descriptor, then any dependent library must either declare that that CheckedException is thrown, caught, or ignored. The emphasis above is used to underscore the utility that my suggestion is trying to convey. I think that with perhaps a few tweaks, this is a flexible suggestion. Although I do not (not yet perhaps... I just need a compelling reason to) know much about Java modules, this system of selectively dealing with checked exceptions appears as a very good candidate for expression there. These are just suggestions and I put them out there because someone with some clout in shaping the future of the Java SE API might think these suggestions are worth considering further. Happy to share and perhaps to talk about it here if others share a similar interest. Have a great day. :) Owen.
