javax.sound.midi cant create devices. Use the IAC to create a new midi port and all your midi apps should be able to see it an communicate with it. Including your java app.
To create a new port with the IAC go to the finder and look for Audio MIDI Setup. In Audio MIDI Setup on the top menu click on "Window" and then on "Show MIDI Window". Double click on the "IAC Driver" icon and you can create the ports you need.