Do a google-search for Java and your platform and find a tarfile distribution compatible with your system Download the tarfile, untar and follow the installation instructions.

You might try www.sun.com or java.sun.com for starters

Also, here is a version of Java EJB for AIX:

http://www.evidian.com/jonas/

Here is more AIX freeware:

http://freeware.bull.net/