使用 BufferReader '\\n' 读取后不会被接受为换行符，如何解决？

Question

I have a large text file I want to format. Say the input file is called inputFile and output file is called outputFile .

This is my code for using BufferedReader and BufferedWriter Here is my code

 public static void readAndWrite(String fileNameToRead, String fileNameToWrite) {
        try{
            BufferedReader fr = new BufferedReader(
                    new FileReader(String.format("%s.txt", fileNameToRead)));
            BufferedWriter out = new BufferedWriter(
                    new FileWriter(String.format("%s.txt", fileNameToWrite), true));
            String currentTmp = "";
            String tmp = "";

            String test = "work \nwork";
            out.append(test);


            while((tmp = fr.readLine()) != null) {
                tmp = tmp.trim();
                if(tmp.isEmpty()) {
                    currentTmp = currentTmp.trim();
                    out.append(currentTmp);
                    out.newLine();
                    out.newLine();
                    currentTmp = "";
                } else {
                    currentTmp = currentTmp.concat(" ").concat(tmp);
                }
            }
            if(!currentTmp.equals("")) {
                out.write(currentTmp);
            }
            fr.close();
            out.close();
        } catch (IOException e) {
            System.out.println("exception occoured" + e);
        }

    }

    public static void main(String[] args) {
        String readFile = "inPutFile";
        String writeFile = "outPutFile";
        readAndWrite(readFile, writeFile);
    }

The problem is that the test string inside the code which have '\\n' can we converted to a new line with BufferedWriter . But if I put the same string in the text file it would not perform the same.

In a more easy way to see is that I want my input file have this

work\n
work

and output as

work 
work

I am using mac, so the separator should be '\\n'

Answer 1

work\n 

if you see the "\\n" in your file, it is not a new line character. It is just two characters.

The trim() method will not remove those characters.

Instead you might have something like:

if (tmp.endsWith("\n")
    tmp = tmp.substring(0, tmp.length() - 2);

I am using mac, so the separator should be '\\n'

You should use the newline character for the platform. So when writing to your file the code should be:

} else {
    currentTmp = currentTmp.concat(" ").concat(tmp);
    out.append( currentTmp );
    out.newLine();
}

The newline() method will use the appropriate new line String for the platform.

Edit:

You need to understand what an escape character is in Java. When you use:

String text = "test\n"

and write the string to a file, only 5 characters are written to the file, not 6. The "\\n" is an escape sequence which will cause the ascii value for the new line character to be added to the file. This character is not displayable so you can't see it in the file.

Answer 2

After @camickr answer, I think I realized the problem. Some how if I have a text in the file like this

work \nwork

The \\n won't be treated as a single char ('\\n'), rather it has been treated as two chars. I think thats why when the BufferWriter writes the input string it won't treat it as a new line.