Officially Java is not supported very well by Player/Stage project. There is some kind of legacy references only.

However you can find Java libraries on separate project: http://java-player.sourceforge.net/
You should check out source code from SVN.
Some basic examples are also available on this site.

Latest version of this library (javaclient3) works well with Player versions 3+
Also there are several bugs in "uncommon" interfaces, like actarray, graphics3d, etc. 
If you are interested in fixes, I can try to extract patch from my local code of the library.

P.S. Another answer was submitted while I was writing my e-mail. :)

2012/8/12 Claudio Carbone <erupter@libero.it>
I would like to try using java with player/stage.
What is the situation regarding this language?
I found references to a java player client, as well as to some java classes at this page

but I don't have a javaclient folder in that path (latest player 3.1.0-svn)

Claudio Carbone

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