Question

I am trying to update a file using Java with new data. Let ‘s say I have a txt file where I have saved the following data:

id     grade
3498   8
2345   9
5444   7
2222   5

So I am trying to update the grade, depending the id the user has typed, but the new (updated) file has the type that follows:

id   grade3498   62345   95444   72222   5

and so on….

I can t find the reason why this is not working, I guessed it has something to do with not adding a new line while re-writing the data, but even if I add new line character (“\n”) in outobj.write(fileContent.toString()); nothing changes.

Here is a snippet of my code :

public String check(int num) throws RemoteException
{
    String textinLine;
    String texttoEdit;
    File file=new File ("c:\\students.txt");
    FileInputStream stream = null;
    DataInputStream in =null;
    BufferedReader br = null;
    try
        {
        stream = new FileInputStream(file);
        in =new DataInputStream(stream);
        br = new BufferedReader(new InputStreamReader(in));
        StringBuilder fileContent = new StringBuilder();
        if ((num>0) && (num<6001))
            {
            while ((textinLine=br.readLine())!=null)
                {
                texttoEdit=Integer.toString(num);
                    System.out.println(textinLine);
                    String[] parts = textinLine.split(" ");
                    if (parts.length>0)
                        {
                        if (parts[0].equals(texttoEdit))
                            {
                            int value =       Integer.parseInt(parts[1]);
                            value-=2;
                            String edit=Integer.toString(value);
                            String newLine = "\n"+parts[0]+"    "+edit+"\n";
                            msg="You can pass2";
                            fileContent.append(newLine);
fileContent.append("\n");               }
                        else
                            {
                            fileContent.append(textinLine);
fileContent.append("\n");
                            }
                        }
                }
            }
        in.close();
        FileWriter fstream = new FileWriter(file);
        BufferedWriter outobj = new BufferedWriter(fstream);
        outobj.write(fileContent.toString());
        outobj.close();
        }
    catch (FileNotFoundException e)
        {
        e.printStackTrace();
        }
    catch (IOException e)
        {
        e.printStackTrace();
        }

Finally, let me say that the new file is rightly edited, which means that if the user enters the id 3498, the grade value would change to 8-2=6, but the new file will be in a single line, as I explained before.

Answer 1

On some OS (typically Windows) you need to use \r\n for a new line. Even better, you can use:

String newLine = System.getProperty("line.separator");

for the line separator which will adjust depending on the platform it is run on.