#Troubleshooting
I had a lot of problems getting Processing to successfully communicate over Serial.
First I had a version mismatch which gave me this error:
WARNING: RXTX Version mismatch Jar version = RXTX-2.2pre1 native lib Version = RXTX-2.2pre2
I found the solution [https://groups.google.com/forum/?fromgroups#!topic/makerbot/fPI_saNgsbM|here] which required installing the new version of RXTX for Java. After that was installed, I got a cryptic PortInUseException on my Mac when running the sketch. I found the solution [http://jgrasstechtips.blogspot.com/2008/04/rxtx-and-funky-portinuseexcep...|here]; I needed to add a folder "/var/lock/" which did not exist on my machine and then change the file permissions for that folder. After opening Terminal, this is what I typed to fix the problem:
cd /var sudo mkdir lock [enter your password] sudo chmod 777 lock [enter your password if prompted]