Many Java-related questions have code blocks in Java properties file format. Right now, in order to ensure they're not improperly highlighted as Java code, the plain text
lang-none language code can be used.
That being said, highlight.js has support for the Java properties file format, even though Stack Exchange does not. It seems ideal if Stack Exchange would add support for the Java properties file format.
That all being said, I understand that the current implementation of language highlighting limits how many languages can be supported due to performance concerns.
Syntax highlighting happens on the client side currently. This means that if we add too many different languages, the size of the distributable gets very large and can make the site slower to load. While any one language might be a good addition, we get enough language requests that if we added them all, we'd have a long list and a big problem.
I'm sure that there are other languages with higher priority to the community than this one. That said, I'm creating this request to get it out there and on the radar so that when language support is optimized in the future, it will be a known desired language.