By default, we use a Groovy script that looks for a class with a `main` method and executes it for running Java programs. For this setup to work correctly, we need to set the `JAVA_HOME` environment variable and make sure that `$JAVA_HOME/jre/lib/amd64/jvm.cfg` is accessible from the isolate sandbox (the file can be a link to a file in a folder in `/etc`, which also needs to be bound to the sandbox).