The Gtk+ look and feel using openjdk

I just did some further experiments with my ruby-processing file chooser, and now I think the "Gtk+" look and feel might be the way to go on linux:-

However it is not that you should call the "Gtk+" look and feel, you should probably call "Metal", but specify system wide that the system and default look and feel is GTK (on archlinux you can do this in /etc/jre.sh in others you might use a flag or otherwise specify an environmental variable, be sure to set GTK fonts too).