I've tried a few libraries and the best one seems to be themidibus

There is a callback function called rawMidi(byte[] data)

First byte contains status so type of message - it will be different for note ons and offs on different channels. The third one will contain velocity which you can ignore if you don't want it, and the second one will contain your note so by typing

1. void rawMidi(byte[] data) {
2.  if (byte[0]==144)                     // looking for note on - channel one
3.            println(" note nr "+byte[1]+" has been triggered with velocity "+byte[2]);
4. }

you can solve your problem