将新行添加到BufferedWriter

Question

I'm trying to write to a text file with each successive call to writeMore() writing to a new line if true is passed as the last argument. However, the writer keeps writing to the end of the same first line. I don't understand what the problem is.

package FileIO;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

public class Buffered_Writer {

    public static void main(String[] args) throws IOException{

        String fileName = "myFile.txt";
        String message = "I'm written into the file.";

        File myFile = new File("C:\\Users\\User\\Desktop\\" + fileName);
        try {
            myFile.createNewFile();
        } catch (Exception e) {
            System.out.println("Could not create file!");
        }


        BufferedWriter writer = new BufferedWriter(new FileWriter(myFile, true));
        writer.write(message);

        writeMore("This much more has been written.", myFile, true);

        writer.close();
    }

    public static void writeMore(String message, File file, boolean newLine) throws IOException{

        BufferedWriter writer = new BufferedWriter(new FileWriter(file, true));
        if (newLine) {
            writer.append(" \n");
            writer.append(message);
        }
        else {
            writer.append(" " + message);
        }
        writer.close();
    }
}

Answer 1

Why not use the proper method

https://docs.oracle.com/javase/7/docs/api/java/io/BufferedWriter.html#newLine()

As per the javadocs

Writes a line separator. The line separator string is defined by the system property line.separator, and is not necessarily a single newline ('\\n') character.

Answer 2

Given

File myFile = new File("C:\\Users\\User\\Desktop\\" + fileName);

I can deduce you are on Windows. The Windows line separator is not \\n (it is \\r\\n but don't hardcode that). Use System.lineSeparator() instead. Change

writer.append(" \n");

to

writer.append(System.lineSeparator());

Answer 3

The best solution is to use BufferedWriter.newLine() method. Additionnaly, do BufferedWriter should be closed properly (using try with resources ):

public static void writeMore(String message, File file, boolean newLine) throws IOException {
    try (BufferedWriter writer = new BufferedWriter(new FileWriter(file, true))) {
        if (newLine) {
            writer.newLine();
            writer.append(message);
        } else
            writer.append(" ").append(message);
    }
}