I found something on http://docs.openhab.org/installation/index.html:
Make sure to use the 32-bit version of the JVM for ARM platforms, even on 64-bit operating systems. Serial connections won’t work with a 64-bit JVM, preventing bindings like Z-Wave from functioning.
The problem is that openhab is not fully working on 64bit java on arm. So the solution is to install the 32bit arm jre which can be found at oracle.
To make the 32bit binaries work some additional commands are needed:
sudo dpkg --add-architecture armhf
sudo apt-get update
sudo apt-get install libc6:armhf