reading a file by lines

[Guadalupe Ortiz]

I works a lot with java, but I still have not clear anything about files. Can anybody send me a few lines describing how to read a text file by lines and how could I delete any of the lines or change it content or add a new line?

Thank-you very much
Gobellot

[Vicken Karaoghlanian]

I wrote this a long time ago, i hardly remember what it does, it needs a little bit modifications to suit your need, but it�ll help you to get started. Good Luck.

private void readWriteFileLine(String src, String dst) {
 
try {

FileWriter fw =  new FileWriter(dst);
BufferedWriter bw = new BufferedWriter(fw);

FileReader fr = new FileReader(src);
BufferedReader br = new BufferedReader(fr);
LineNumberReader lnr = new LineNumberReader(br);

String line = null;

while ( (line = lnr.readLine()) != null ) {

int lineNo = lnr.getLineNumber();

if ((line.length() != 0) && (line.charAt(0) == pageBreak)) {
lnr.setLineNumber(1);
}

if (lineNo >= 9 && lineNo != 15) {
line = modifyLine(line);
}


bw.write(line);
bw.newLine();
}

lnr.close();
br.close();
bw.close();

} catch (java.io.FileNotFoundException e) {
System.out.println("Error opening source file");

} catch (java.io.IOException e) {
System.out.println("Error writing to destination file");
}
}

[ May 15, 2004: Message edited by: Vicken Karaoghlanian ]

[Guadalupe Ortiz]

Thank-you very much. I have tried the code and now I know how to read a file by lines and how to append information to the end of a file, but I still have one doubt. I got a file and I desire to modify the content of a determinated file (simply delete that line in instead writting a new information at that line) �Is there anything similiar to the "lineNumberReader" for writting in a line number? If not, is there any other function for that?
thanks again for your help
Gobellot

[Vicken Karaoghlanian]

I don't think it is possible to modify the original file directly. You can however, read the input file line-by-line then write it back to another output file with your modified lines, afterwards you can simply overwrite the input file with the output file. This is the only approach i am aware of, and i am almost certain that it can't be done any other way.

Tip: If you are dealing with small sized files, you can read the entire file into memory, and do your entire modifications there; this will improve the performance of your application.

[Gregg Bolinger]

Moving this to I/O And Streams...