read/write a file and '\n' problem

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  • mickey0
    New Member
    • Jan 2008
    • 142
    #1

    read/write a file and '\n' problem

    Hi,
    I have one problem; I must read a html like this;
    Code:
    <html>
<body>
Hello
</body>
</html>
    I read this in a string (correct?) and after I have to do some changes to it and write it on disk but in this way:
    Code:
    <html>\n<body>\nhello\n</body>\n</body>
    There, there's the '\n' because in the original file <body> was in another line of <html>
    How can I do this? This my code for read and write:
    Code:
          File fin = new File(FILE_NAME);    
                  FileReader in = new FileReader(fin);           
                  istream =  new BufferedReader( in );                                               
                  String line = null;                 
                  while ( (line = istream.readLine()) != null  ) {
                      //System.out.println(line);
                      sb.append(line);
                  }
                              // here do changes on the sb
                              String text = sb.toString();
                  FileWriter fw = new FileWriter(new File ("out.txt") ); 
                  out = new PrintWriter(fw); 
                  out.println(text);
    Thanks
    Tags: None
    • JosAH
      Recognized Expert MVP
      • Mar 2007
      • 11453
      #2
      The readLine() method returns a String without the terminating end of line character
      sequence so you have to append that sequence yourself after you have appended
      the line String to your StringBuffer (or StringBuilder). Look at the system properties
      for the correct value of the end of line character sequence.

      kind regards,

      Jos

        Comment

        • mickey0
          New Member
          • Jan 2008
          • 142
          #3
          is there any other "read" method that don't get out '\n' ???

            Comment

            • JosAH
              Recognized Expert MVP
              • Mar 2007
              • 11453
              #4
              Originally posted by mickey0
              is there any other "read" method that don't get out '\n' ???
              Sure, you can read parts (or all) of the file directly into a char[] of CharBuffer if
              you want. Read the API documentation for details. Note though that an end of
              line character sequence need not be a single \n character so don't anticipate
              on that.

              kind regards,

              Jos

                Comment

                • mickey0
                  New Member
                  • Jan 2008
                  • 142
                  #5
                  to be sincer, for me it's not important to read the file line by line; how can I put the entire file into a String in a hit?

                    Comment

                    • JosAH
                      Recognized Expert MVP
                      • Mar 2007
                      • 11453
                      #6
                      Originally posted by mickey0
                      to be sincer, for me it's not important to read the file line by line; how can I put the entire file into a String in a hit?
                      Read the API documentation for the BufferedReader and Reader classes.
                      You'll find the read() methods you need.

                      kind regards,

                      Jos

                        Comment

                        • mickey0
                          New Member
                          • Jan 2008
                          • 142
                          #7
                          hello,
                          read() is ok; but as you can see I have ither problem because I'm a newbie to java; doesn't exist any function like c++ seekg() to seek at the end of my file and retrive the number of characters it has?
                          Code:
                          char buf[] = new char[100];
int num = istream.read(buf, 0, 100);
                          It's my code but I can't have a fixed dimesion for buf (I mean, 100)....
                          Can you suggest me more? thanks...

                            Comment

                            • drsmooth
                              New Member
                              • Oct 2007
                              • 112
                              #8
                              if you use readLine(), you can assume that there is a '\n' character after each call, im not sure how that fits into your program, but if you had a loop like:

                              Code:
                                                while ( (line = istream.readLine()) != null  ) {
                      //System.out.println(line);
                      sb.append(line);
                  }
                              you could use something like
                              Code:
                               line+= '\n' ;
                              prior to appending it to whatever you are doing.

                              im not sure if that helps, but i hope it did

                              good luck,
                              ken

                                Comment

                                • Nepomuk
                                  Recognized Expert Specialist
                                  • Aug 2007
                                  • 3111
                                  #9
                                  Originally posted by drsmooth
                                  if you use readLine(), you can assume that there is a '\n' character after each call...
                                  That is not 100% correct - there won't be a '\n' character after the last line. So you should use something like this:
                                  Code:
                                  read first line
while (there is a next line)
{
   add '\n' to your String
   read the next line and add it to the String
}
                                  or alternatively:
                                  Code:
                                  while(something)
{
   read next line
   if there's a next line, add '\n'
   else quit the loop
}
                                  Greetings,
                                  Nepomuk

                                    Comment

                                    • BigDaddyLH
                                      Recognized Expert Top Contributor
                                      • Dec 2007
                                      • 1216
                                      #10
                                      Originally posted by mickey0
                                      hello,
                                      read() is ok; but as you can see I have ither problem because I'm a newbie to java; doesn't exist any function like c++ seekg() to seek at the end of my file and retrive the number of characters it has?
                                      Don't forget that the number of bytes is not necessarily the number of chars -- for example, my favorite encoding for HTML, UTF-8.

                                        Comment

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