I'm a plugin developer and I want to know what version of Java most Bukkit servers are running on so that my plugins will be compatible. I've been compiling all of my plugins for Java 7 so far since that's what's installed on my development environment. However I'm aware that this is not backwards-compatible with Java 6, so I'm wondering if it's worth setting up a Java 6 build environment. If you don't know what version of Java you're on but you have access to your server's command line, try running "java -version" without the quotes. The response should contain a version number beginning with either "1.6" for Java 6 or "1.7" for Java 7. If your server is with a server host and you don't know what version of Java they run, answer "I don't know".