You need to import the serial library before you can use functions/objects from it.  You can do this by adding the line

Thanks!

Hey,
i think you try to run an arduino-program in processing. That won't work. You have to upload this programm to your arduino-board with the arduino-software (which looks very similiar).
Then, if you want to read the data with processing, you will need to run a sepreate sketch in processing.

Good catch! I didn't read past the setup()...