code: public void clear(String what) 
  	{ 
  		if (what.equals("blockers")) blockers.clear(); 
  		else if (what.equals("datasets")) datasets.clear(); 
  		else if (what.equals("learners")) learners.clear();
  		else if (what.equals("all")) {
  			clear("blockers"); clear("datasets"); clear("learners");
  		} else {
  			System.out.println("usage: clear blockers|datasets|learners|all");
  		}
  	}
docs: Clear datasets, blockers, or learners.