Netbeans 如何修复octaplanner类ConferenceSchedulingConstraintProvider.java中的错误？

Netbeans指向类ConferenceSchedulingConstraintProvider.java int ht方法中的错误：

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);
}

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您的语言级别可能未设置为至少

Java8

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打开项目设置并将其设置为java 8或更高版本。

错误在哪一行？什么类型的错误？请格式化您的代码，指定错误消息以及错误发生的位置。