How can I normalize the EOL character in Java?

I have a linux server and many clients with many operating systems. The server takes an input file from clients. Linux has end of line char LF, while Mac has end of line char CR, and Windows has end of line char CR+LF

The server needs as end of line char LF. Using java, I want to ensure that the file will always use the linux eol char LF. How can I achieve it?

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Combining the two answers (by Visage & eumiro):

EDIT: After reading the comment. line. System.getProperty("line.separator") has no use then.
Before sending the file to server, open it replace all the EOLs and writeback
Make sure to use DataStreams to do so, and write in binary

String fileString;
//..
//read from the file
//..
//for windows
fileString = fileString.replaceAll("rn", "n");
fileString = fileString.replaceAll("r", "n");
//..
//write to file in binary mode.. something like:
DataOutputStream os = new DataOutputStream(new FileOutputStream("fname.txt"));
os.write(fileString.getBytes());
//..
//send file
//..

the replaceAll method has two arguments, the first one is the string to replace and the second one is the replacement. But, the first one is treated as a regular expression, so, '' is interpreted that way. So:

"rn" is converted to "rn" by Regex
"rn" is converted to CR+LR by java

---

你可以试试吗？

content.replaceAll("rn?", "n")

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Had to do this for a recent project. The method below will normalize the line endings in the given file to the line ending specified by the OS the JVM is running on. So if you JVM is running on Linux, this will normalize all line endings to LF (n).

Also works on very large files due to the use of buffered streams.

public static void normalizeFile(File f) {      
    File temp = null;
    BufferedReader bufferIn = null;
    BufferedWriter bufferOut = null;        

    try {           
        if(f.exists()) {
            // Create a new temp file to write to
            temp = new File(f.getAbsolutePath() + ".normalized");
            temp.createNewFile();

            // Get a stream to read from the file un-normalized file
            FileInputStream fileIn = new FileInputStream(f);
            DataInputStream dataIn = new DataInputStream(fileIn);
            bufferIn = new BufferedReader(new InputStreamReader(dataIn));

            // Get a stream to write to the normalized file
            FileOutputStream fileOut = new FileOutputStream(temp);
            DataOutputStream dataOut = new DataOutputStream(fileOut);
            bufferOut = new BufferedWriter(new OutputStreamWriter(dataOut));

            // For each line in the un-normalized file
            String line;
            while ((line = bufferIn.readLine()) != null) {
                // Write the original line plus the operating-system dependent newline
                bufferOut.write(line);
                bufferOut.newLine();                                
            }

            bufferIn.close();
            bufferOut.close();

            // Remove the original file
            f.delete();

            // And rename the original file to the new one
            temp.renameTo(f);
        } else {
            // If the file doesn't exist...
            log.warn("Could not find file to open: " + f.getAbsolutePath());
        }
    } catch (Exception e) {
        log.warn(e.getMessage(), e);
    } finally {
        // Clean up, temp should never exist
        FileUtils.deleteQuietly(temp);
        IOUtils.closeQuietly(bufferIn);
        IOUtils.closeQuietly(bufferOut);
    }
}

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