Netbeans указывает на ошибку в классе ConferenceSchedulingConstraintProvider.java int ht метод:
private Constraint talkPrerequisiteTalks(ConstraintFactory factory) {
return factory.from(Talk.class)
.join(Talk`enter code here`.class,
containing(Talk::getPrerequisiteTalkSet, Function.identity()),
lessThan(talk1 -> talk1.getTimeslot().getStartDateTime(),
talk2 -> talk2.getTimeslot().getEndDateTime()))
.penalizeConfigurable(TALK_PREREQUISITE_TALKS,
Talk::combinedDurationInMinutes);
}