code: public static void main(String[] args) throws Exception {
  
          // httpd.conf has this next line:
          //       LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
          String logFormat = "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"";
  
          // Developer suggestion:
          // This is what you do to find out what the possible fields are:
          List<String> possibleFields = ApacheHttpdLogfileInputFormat
                  .listPossibleFields(logFormat, null, null);
          System.out.println("----------------------------------------");
          System.out.println("All possible fields are:");
          for (String field : possibleFields) {
              System.out.println(field);
          }
          System.out.println("----------------------------------------");
  
          System.exit(ToolRunner.run(new Configuration(), new Wordcount(logFormat), args));
      }
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