I uploaded a bot in Java, the build failed without any feedback in the logs, so I tried the reference Java bot which had the same result. (failed without any logging)
We have looked at your java uploads. It seems like the pom is missing. The pom.xml file should be in the root directory of your java bot alongside the bot.json file. I realize it is frustrating that the error logs are not populated in this scenario - sorry about that. I have added a ticket to our backlog to look into improving the output.