Perhaps, most of the time I have not created a general use data structure - just highly specialized ones. Extending would allow no references/indirection but it

Perhaps, most of the time I have not created a general use data structure - just highly specialized ones. Extending would allow no references/indirection but it's rather ugly and it has to provide another function to instantiate (I'd consider reflection, i.e. Class.newInstance() not to be a good way to handle the case).