java - 如何从Java 7中的.txt文件提取主机名和主机请求的出现？

Question

如何使用正则表达式和哈希映射为以下输入文本文件查找主机名和来自同一主机的请求数：

input.txt

     unicomp6.unicompt.net - - [01/JUL/1995:00:00:06 - 0400] "GET /shuttle/countdown/ HTTP/1.0" 200 3985     
     burger.letters.com - - [01/JUL/1995:00:00:12 - 0400] "GET /shuttle/countdown/ HTTP/1.0" 200 0
     d104.aa.net - - [01/JUL/1995:00:00:13 - 0400] "GET /shuttle/countdown/ HTTP/1.0" 200 3985 
     unicomp6.unicompt.net - - [01/JUL/1995:00:00:14 - 0400] "GET /shuttle/countdown/ HTTP/1.0" 200 40310
     d104.aa.net - - [01/JUL/1995:00:00:15 - 0400] "GET /shuttle/countdown/ HTTP/1.0" 200 40310 
     d104.aa.net - - [01/JUL/1995:00:00:15 - 0400] "GET /images/NASA-logosmall.gif HTTP/1.0" 200 786
     unicomp6.unicompt.net - - [01/JUL/1995:00:00:14 - 0400] "GET /shuttle/countdown/ HTTP/1.0" 200 786 
     unicomp6.unicompt.net - - [01/JUL/1995:00:00:14 - 0400] "GET /shuttle/countdown/ HTTP/1.0" 200 1204 

所需的输出：

   unicomp6.unicompt.net 4
   burger.letters.com 1
   d104.aa.net 3

Answer 1

为什么不使用正则表达式？

public static void main(String[] args) {
    Pattern pattern = Pattern.compile("\\w+\\.\\w+\\.\\w+", Pattern.DOTALL);
    String input = "unicomp6.unicompt.net - - [01/JUL/1995:00:00:06 - 0400]"+
                    "burger.letters.com - - [01/JUL/1995:00:00:12 - 0400] .... etc";

    Matcher m = pattern.matcher(input);
    while (m.find()) {
      String s = m.group();
      System.out.println(s);  
    }
}