Start a Java process at low priority using Runtime.exec / ProcessBuilder.start?

I'm trying to start an external process via Java using the ProcessBuilder class, and that much works. Currently running using the command:

new ProcessBuilder("java", "-jar", jarfile, args);

What I would like to do is just this, but to start the process with low priority. My program is currently only running on Windows, so a window-specific solution is fine by me. Some research suggests I use the "start" command, but when I try doing this from Java it gives an exception saying it is an unrecognized command (the same command works from cmd.exe).

Does anyone know how to launch a process from Java (Windows-specific if need be), with belownormal priority?