I was able to fix the problem and I thought I it might be useful for future users if I comment what was happening.
Apparently what was happening is that I was trying to load the example from /usr/local/.../examples
which is the default installation directory. But in Unix based systems this directory is read-only. When I copied the directory to another location with read-write permissions, it was able to load the example.
I have two suggestions:
1) It might be a good idea to add explicitly this step to the documentation ( the step of copying the directory to another location with more permissions).
2) The error shown should be something more descriptive of the problem itself and not a java null pointer error.
I hope this helps someone :)