1.　　使用DFA实现词法分析器的设计；

2.　　实现对Java源程序中注释的过滤；

3.　　利用两对半缓冲区从文件中逐一读取单词；

4.　　词法分析结果属性字流存放在独立文件(文件名：scanner_output)中；

5.　　统计源程序每行单词的个数和整个源文件单词个数；

6.　　具有报告词法错误和出错位置（源程序行号和该行字符）的功能；-1. Using DFA realize the design of the lexical analyzer　2. To realize the Java source code in the comment filter　3. Use of two pairs of semi-buffer from the file one by one to read the words　4. Lexical analysis of word attributes stored in a separate stream file (file name: scanner_output) in　5. Statistics source the number of words per line and the source file number word　6. a report lexical errors and error location (source code line number and character of the line) functions