I was trying out my little Java VoIP application with a friend of mine who owned a Macintosh, and it didn't quite work right. Besides the whole dubious Java 5.0 support for the Macintosh, I couldn't open a TargetDataLine at 8000 kHz.
On PCs, you can record and playback audio at arbitrary sample rates. That's not the case on the Macintosh. After getting another friend to do some probing, I found that the Java sound system on Macintoshes can playback at arbitrary sample rates, but can only record at 44100 Hz. You can record at 8/16-bit depths, with (un)signed types, and at different endianness though, I think.