java编写的上下文无关文法分析程序，图形界面，JBuilder运行环境，Eclipse也可，可以选择文件读取也可以自己输入。判断是否为空。形式语言与自动机的课程作业。-context-free grammar written in java parser, graphical interface, JBuilder runtime environment, Eclipse is also possible to select the file you can read their input.