1、LOOKAHEAD()
https://blog.csdn.net/qingmengwuhen1/article/details/83313303
https://blog.csdn.net/zyb243380456/article/details/7242796
IF-ELSE语句的翻译中选择冲突解决：https://www.cnblogs.com/orlion/p/7157909.html
2、JavaCC语法规则
https://wenku.baidu.com/view/f9df457f4431b90d6d85c731.html