Edit 2017-04-27: I have been disappointed by the lack of forward momentum for jpm4j, and the lack of community-centric development. So I invented a new tool called jrun. I invite everyone to check it out. It has a narrower scope than tools like Python's pip, but it does let you execute Java code from remote Maven repositories in an easy-to-use manner.
Check out JPM4J. It is a project by Peter Kriens (of BND fame). He first proposed it last year, and as of this writing it has been around for a few months and is looking pretty impressive.
It was inspired by Node's npm, and like that tool, installation is a cinch:
OS X:
local $ curl http://www.jpm4j.org/install/local | sh
global $ curl http://www.jpm4j.org/install/global | sudo sh
Linux:
curl http://www.jpm4j.org/install/script | sh
And Windows has a clicky installer, of course.
Then you install stuff similarly to other command-line package manager tools. E.g.:
jpm install org.codehaus.groovy:groovy-all
The install command operates Maven coordinates. Basically, the JAR just needs a JPM-Command entry in its manifest, and jpm knows how to expose its main class as a command-line executable.
Personally I would really love to see the Java community get behind an effort like this. A really solid Java package manager is years overdue!
