ahem GOOGLE!
What is it: Maven is a build automation tool for java.
In simple terms: Source code and config file listing dependencies goes in, magic, then compiled code comes out.
Other fancy stuff is available like: * running unit tests to ensure bugs don't reappear in your code. * processing files before compiliation * bundling libraries into the final jar.
http://en.wikipedia.org/wiki/Apache_maven
It works with pretty much every OS that supports java.
Tutorials and instructions, see links above, google and youtube.