Why I can't print the content of this StringBuffer object after that I have append into it the lines of a readed file?

Question

I have the following problem. I have create a method that read a very big textual file starting by its path.

The file is read line by line and each line is appended into a StringBuffer.

This is my code:

public void run(Vector parametri) {

    if (parametri != null && (parametri.isEmpty() == false)) {
        gvParam = (Vector) parametri.clone();
    } else {
        TraceLog.scrivi("Test Esistenza Parametri", "Parametri mancanti", false, TraceLog.lowConsole + TraceLog.highTrace + TraceLog.highLog);
        target.azione("Parametri mancanti !!");
        return;
    }

    String fattureXml = gvParam.get(0).toString();

    // READ THE FILE:   
    StringBuffer fileContent = new StringBuffer();

    try {
        // Creazione del reader per leggere il file:
        BufferedReader br = new BufferedReader(new FileReader(fattureXml));

        String line = null;

        while ((line = br.readLine()) != null) {
              //System.out.println(line);

              fileContent.append(line);
        } 

        System.out.println(fileContent.toString());


    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }   

}

The reading section begin after the comment // READ THE FILE:

The file read seems work fine because I used this line (actually commented)

System.out.println(line);

to check the readed line and it read it correctly.

As you can see now I am adding this line to a StringBuffer (to obtain a big String representing the content of the readed file), by:

fileContent.append(line);

The problem is that, after the loop, I am trying to print in the console the content of the fileContent StringBuffer, by:

System.out.println(fileContent.toString());

but nothing is printed.

Why? What am I missing? What exactly contains the fileContent StringBuffer? Is it something like a big String containing the lines of the readed file or what?

(1) You could use a debugger and inspect the variables in the loop to see what's going on. (2) Vector and StringBuffer are osbolete (3) You should use generic instead of raw types (`Vector` instead of just `Vector`) (4) it may be a problem with your console not being able to print such a large string at once.... — assylias, Jun 09 '15 at 15:04
@assylias I am working on a very very old legacy application (welcome back in the 90s...) and I can't change it :-( — AndreaNobili, Jun 09 '15 at 15:06

score 4 · Accepted Answer · edited May 23 '17 at 12:14

Here's my guess: Since you're discarding all new-line characters, you end up with a single enormously long line, which your console is having troubles handling. (I've experienced this myself in the Eclipse console.)

Try changing

fileContent.append(line);

to

fileContent.append(line).append('\n');

As @assylias points out you also might want to drop Vector (and use for instance an ArrayList instead). Also, have a look at this question: Difference between StringBuilder and StringBuffer.

For future reference, the "modern" way of doing this would be

String content = new String(Files.readAllBytes(Paths.get(fileName)));

Wild but reasonable guess :-) – assylias Jun 09 '15 at 15:06 — assylias, Jun 09 '15 at 15:06

Why I can't print the content of this StringBuffer object after that I have append into it the lines of a readed file?

1 Answers1