code: public void checkIfProblemFactsExist() {
          if (problemFactCollectionMemberAccessorMap.isEmpty() && problemFactMemberAccessorMap.isEmpty()) {
              throw new IllegalStateException("The solutionClass (" + solutionClass
                      + ") must have at least 1 member with a "
                      + ProblemFactCollectionProperty.class.getSimpleName() + " annotation or a "
                      + ProblemFactProperty.class.getSimpleName() + " annotation"
                      + " when used with Drools score calculation.");
          }
      }
docs: Only called if Drools score calculation is used.