RadioStation is a small but functional streaming MP3 server written in pure Java. In other words, it lets you broadcast high-quality MPEG audio across the Internet or a LAN, whatever operating system you're running.
It is provided by Apple Computer as MRJ sample code, to provide developers with a (hopefully) clearly-written example of a multithreaded networked server application, of some nontrivial producer/consumer synchronization, and of how to use Java file I/O to parse complex data formats like MPEG and ID3. The source code is provided, and you may use and modify it as you wish (see my note on the license.)
RadioStation was also developed to test MRJ's stability. An iMac in the MRJ team's lab has been running it since November. Almost the only downtime has been as necessary to upgrade the application, the MRJ version, or the OS. Listening to music has been a very pleasant way to test MRJ!
When I began development, there were no streaming MP3 servers for platforms other than Windows and Unix. (There is now a native Mac MP3 server called iStream.) In classic hacker fashion, I wrote RadioStation to "scratch an itch": I wanted to broadcast ambient and techno music from my Mac for the amusement of my co-workers. RadioStation should also work on BeOS, OS/2, AmigaOS, etc. as well as the usual Windows and Unix, although it hasn't yet been tested on anything but Mac OS. If you can graft enough mass storage onto a Java ring, it might even work there!