Developers' Forum

I'm personally happy with the current way that warnings are handled. I haven't taught Java for many years, but in my C course I always required students to submit code that compiled without warnings. Any warnings meant zero marks. I even added the -Wall option for even more warnings! But penalties for resubmission were fairly low so students could resubmit warning-free code without paying a high price. 

However, your situation may be different, so ...

As a starting point, to get a feel for what's possible, create a new write-a-program question of type 'multilanguage'. Customise it, and pull out all the non-Java-relevant code. Under Advanced Customisation, set the Ace language to Java rather than a comma-separated list of options. That will lock the question into Java only and the language-select dropdown will disappear.

Now it's over to you to decide exactly how you want the compile-and-run process to work in the presence of compiler warnings. One option might be to check for the presence of a .class file after the compile phase and proceed to run the code if it's present, rather than abort if the compiler gives a non-zero return code. But you'd still have the compiler warnings present in your got column, so the student would still fail the tests. To prevent that you'd have to change the script to capture the actual compiler output. The relevant line here is "return_code = subprocess.call(['javac', "-J-Xss64m", "-J-Xmx4g", filename])": change that to a more-generic subprocess.run (see documentation here) in which you capture the stdout and stderr output. You could filter the stderr output to remove lines beginning with 'Note:' and print the rest to stdout. That should, if I understand the Java compiler properly (which I don't) give you only genuine syntax errors rather than warnings. 

Once you've got it working the way you want, you could make it into a new question type (or several types, adding appropriate extra Java code for 'write-a-function', 'write-a-class', 'write-a-program' questions as appropriate). They could be question types like Java_program_allow_warnings, Java_class_allow_warnings etc. 

If you want to get real fancy, you could make it into a combinator template grader, and give fewer marks if students submit code that generates warnings :-) But that's much harder.

And after writing all that, I do still wonder why you'd want students to submit code that uses unsafe or unchecked operations! :-)