Write different lines to file

Question

I have this method that writes to a file every time it's called:

public void writeToFile(String ins) {
    FileWriter fw = new FileWriter(f);
    BufferedWriter bw = new BufferedWriter(fw);

    bw.write(ins);
    bw.newLine();

    bw.close();
    fw.close();
}

But it only writes on the very first line of the file.

So, if I called it once with "Hello" and then again with "World", the file would contain "World", but the result I'm looking for is:

Hello

World

I tried using BufferedWriter.newLine() before and after writing the string but the result is the same?

Did you check the documentation for `FileWriter`? Check out the second argument to the constructor: https://docs.oracle.com/javase/7/docs/api/java/io/FileWriter.html#FileWriter(java.io.File,%20boolean) (In other words, you want to `append` to a file, not write/overwrite it) — domsson, May 08 '17 at 13:38
Possible duplicate of [How to append text to an existing file in Java](http://stackoverflow.com/questions/1625234/how-to-append-text-to-an-existing-file-in-java) — Tom, May 08 '17 at 13:39
http://stackoverflow.com/questions/1625234/how-to-append-text-to-an-existing-file-in-java — AppX, May 08 '17 at 13:40
Beyond that: you got various answers by now; please pick one to accept. — GhostCat, May 09 '17 at 06:49

score 3 · Answer 1 · answered May 08 '17 at 13:39

read the documentation of FileWriter:

FileWriter(File file, boolean append) Constructs a FileWriter object given a file name with a boolean indicating whether or not to append the data written.

and you see, that you need to set the append value to true:

FileWriter fw = new FileWriter(f, true);

score 3 · Accepted Answer · answered May 08 '17 at 13:40

3

You have to use FileWriter(String fileName, boolean append)

FileWriter fw = new FileWriter(f, true);

answered May 08 '17 at 13:40

Youcef LAIDANI

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GhostCat · Answer 3 · 2017-05-08T13:45:35.273

2

The point is: your code does what it is supposed to do - it uses a FileWriter, which by default will create a new, empty file; it writes one string; and closes the FileWriter.

If you want to write more than one line; you either have to

use the FileWriter in APPEND mode when doing later writes (by using that second, boolean argument for the FileWriter constructor with true)
change your method to take a list of strings, and write all of them at once

edited May 08 '17 at 13:45

answered May 08 '17 at 13:40

GhostCat

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I like that statement : "your code does what it is supposed to do" It is usually true, but the dev don't code what it is supposed to be done ;) – AxelH May 08 '17 at 13:51

score 2 · Answer 4 · answered May 08 '17 at 13:50

you can use a escape character:

\b Insert a backspace in the text at this point.
\n Insert a newline in the text at this point.
\r Insert a carriage return in the text at this point.

I recommend you to use resource try to allow java to close the file when it will necessary

public void writeToFile(String ins) {

    String fileName= "file.txt";

    try (FileWriter fileWritter = new FileWriter(fileName, true)) {

        fileWritter.write(ins + "\r\n");

    } catch (IOException ex) {

    }
}

give to this method a empty string "" to insert in the file a "Enter"

Write different lines to file

4 Answers4