Thumb of a rule:

Thumb of a rule:
- don't set default values, let it fail with an NPE if not taken correctly care of.
- if a default value is set, the mistake of careless will be spotted very much later  (e.g. when the data is already persisted).
- if no default value is set (in this case it makes sense not set ...) an NPE is likely be thrown which might be spotted much earlier.
- this is good as bugs/bad data are detected (prevented in the end) earlier, too.