[rules-users] BEST_FIT Null Pointer Exception

I am currently using final 6.0 and I used <constructionHeuristicType>BEST_FIT</constructionHeuristicType> but after I have run it propmts java.lang.NullPointerException pointing to my PlanningVariableStrengComparator. Did I miss something? My planning variable comparator by the way is : public class MyVariableStrengthComparator implements Comparator<MyVariable>, Serializable { public int compare(MyVariable a, MyVariable b) { return new CompareToBuilder() .append(a.getId(), b.getId()) .toComparison(); } } -- View this message in context: http://drools.46999.n3.nabble.com/BEST-FIT-Null-Pointer-Exception-tp40269... Sent from the Drools: User forum mailing list archive at Nabble.com.