TL;DR: The Java implementation doesn't have generated flatbuffers code under source control, and the code generation depends on an unofficially-maintained Maven artifact. Other language implementations do check in the generated code; would it make sense for this to be done for Java as well?
I'm currently focusing on Java development; I started building on Windows and got a failure under java/format, because I couldn't download the flatbuffers compiler (flatc) to generate Java source. The artifact for the flatc binary is provided "unofficially" (not by the flatbuffers project), and there was no Windows version, so I had to jump through hoops to build it and proceed. I wanted to document this procedure (see https://issues.apache.org/jira/browse/ARROW-12006) but I was curious to know this affects other implementations, and I found that these languages have generated flatbuffers code checked in: - C++ - JS - Rust - C# I would like to consider adding Java to the list; this would eliminate a hurdle for Java developers under Windows, and eliminate depending on the unofficial artifact provided for other platforms (which BTW, is at 1.9, behind the 1.12 version used by other languages). Let me know if this makes sense, or if I'm missing something.