Strings written to file do not preserve line breaks

By | July 12, 2018
Questions:

I am trying to write a String(lengthy but wrapped), which is from JTextArea. When the string printed to console, formatting is same as it was in Text Area, but when I write them to file using BufferedWriter, it is writing that String in single line.

Following snippet can reproduce it:

public class BufferedWriterTest {
    public static void main(String[] args) throws IOException {
        String string = "This is lengthy string that contains many words. So\nI am wrapping it.";
        System.out.println(string);
        File file = new File("C:/Users/User/Desktop/text.txt");
        FileWriter fileWriter = new FileWriter(file);
        BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
        bufferedWriter.write(string);
        bufferedWriter.close();
    }
}

What went wrong? How to resolve this? Thanks for any help!

Answers:

Text from a JTextArea will have \n characters for newlines, regardless of the platform it is running on. You will want to replace those characters with the platform-specific newline as you write it to the file (for Windows, this is \r\n, as others have mentioned).

I think the best way to do that is to wrap the text into a BufferedReader, which can be used to iterate over the lines, and then use a PrintWriter to write each line out to a file using the platform-specific newline. There is a shorter solution involving string.replace(...) (see comment by Unbeli), but it is slower and requires more memory.

Here is my solution – now made even simpler thanks to new features in Java 8:

public static void main(String[] args) throws IOException {
    String string = "This is lengthy string that contains many words. So\nI am wrapping it.";
    System.out.println(string);
    File file = new File("C:/Users/User/Desktop/text.txt");

    writeToFile(string, file);
}

private static void writeToFile(String string, File file) throws IOException {
    try (
        BufferedReader reader = new BufferedReader(new StringReader(string));
        PrintWriter writer = new PrintWriter(new FileWriter(file));
    ) {
        reader.lines().forEach(line -> writer.println(line));
    }
}

Questions:
Answers:

Please see the following question on how to appropriately handle newlines.

How do I get a platform-dependent new line character?

Basically you want to use

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

and then use the newLineChar instead of “\n”

Questions:
Answers:

I just ran your program, and adding a carriage return (\r) before your newline (\n) did the trick for me.

If you want to get a system independent line separator, one can be found in the system propery line.separator

String separator = System.getProperty("line.separator");
String string = "This is lengthy string that contains many words. So" + separator
            + "I am wrapping it.";

Questions:
Answers:

If you are using a BufferedWriter, you could also use the .newline() method to re-add the newline based on your platform.

See this related question: Strings written to file do not preserve line breaks

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