Just a few comments on Gentoo and Java. Of course, Gentoo includes many Java packages. For the most part, installing a Java application works the same way as installing a native application, using the “emerge” tool. The source code for the application is downloaded, compiled using the appropriate settings, and installed, along with any dependent packages. For example, installing the Eclipse IDE and the Tomcat application server, both of which depend on many other Java packages, was a snap (well, maybe not exactly a snap due to the lengthy compilation cycle, but easy nevertheless).
At first, I was slightly surprised that Gentoo decided to compile all Java programs from scratch. After all, all significant Java optimizations occur at runtime, rather than compile time. But it really fits better into the Gentoo philosophy. The following page on the Gentoo Wiki explains some of the reaons for building Java code from source.
The Wiki also contains a page on Java on Gentoo, as well as a nice Gentoo Java roadmap.
As I mainly work with Java, I’m glad to see that it is an important consideration for Gentoo.