Ok, that’s a bit bizarre to choose an OS on it’s appearance without regard for the software available for it or the range of hardware it does or doesnt’ support. The graphical environment of a typical Unix would be an ‘X’ server X11 or Xorg, over the nuts and bolts of the unix / varient OS, then a window manager running on top of X, like Gnome, KDE. Fluxbox, Blackbox, Window Maker and so on.
If you want java and an old looking user interface what about a Linux distro like XUbuntu, you don’t have Gnome or KDE by default and you can choose an older window manager like Window Maker? You get a bang upto date OS, hardware support and flexibility, with an old style interface?
Then if you find Window Maker or Fluxbox is too limiting you can choose Gnome or KDE later and add them without having to do a reinstall of a different OS.
Java is available throughout. Doesn’t have to be Suns OS as well.