我如何从 java 7 中的 .txt 文件中提取主机名和主机请求的出现？

Question

How can I find the host name and the number of requests from the same host using regex and hashmap for the below input text file:

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 

desired output:

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

Answer 1

Why not using a regex ?

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);  
    }
}

Answer 2

you can try this (for Java 8 and beyond):

public static void main(String[] params) throws IOException {

    try (Stream<String> lines = Files.lines(Paths.get("src/main/resources/input.txt"))) {

        Map<String, Integer> occurrences = new HashMap<>();
        lines.map( line -> line.split(" ") )
             .forEach( splitted -> {
                 occurrences.merge(splitted[0], 1, Integer::sum);
             } );

        System.out.print( occurrences );
    }

}

just be careful for path of your txt file