Issue with 'Writing Your First SmartApp'

So I’m (obviously) just starting writing some simple smartapps. I’m having an issue with the walkthrough here:

http://docs.smartthings.com/en/latest/getting-started/first-smartapp.html

Any time I try to run the simulator, and hit the Play button to ‘activate motion’, I get the following Java error:

java.lang.ArrayIndexOutOfBoundsException

What the heck am I missing? It’s basically a C&P!

So even using the ‘Big Turn OFF’ template I get this error.

edit: So it seems the simulator just doesn’t work. Google seems to tell me that problem is quite common.