Java 6 Copy files with readline

Question

I try to copy files with some mandatory parameters : inputEncoding, outputEncoding and outputLineSeparator.

But when I run my following code, my file with the CRLF final char is not well copy, this last CRLF char disapear.

I think readLine return null after line 3 because line 4 is empty...

My goal is to find the copyfile function that could strictly copy this two following files.
Is there a way to copy also this final empty line (the last newline char) ?

Thanks in advance for any help.

Input Files
File testInEndNL.txt(explicit char)

A<CRLF>
B<CRLF>
C<CRLF>

File testOutEndEOF.txt(explicit char)

A<CRLF>
B<CRLF>
C

Output Files
File testOutEndNL.txt(explicit char) KO for me

A<LF>
B<LF>
C

File testInEndEOF.txt(explicit char) OK for me

A<LF>
B<LF>
C

Code

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.nio.charset.Charset;


public class TestEncoding {

    public static void main(String[] args) {
        File src;
        File dst;
        Charset inputEncoding;
        Charset outputEncoding;
        String outputLineSeparator;

        inputEncoding = Charset.defaultCharset();
        outputEncoding = Charset.forName("UTF-16");
        outputLineSeparator = "\n";

        src = new File("C:\\Users\\Dam\\Desktop\\testFiles\\testInEndNL.txt");
        dst = new File("C:\\Users\\Dam\\Desktop\\testFiles\\testOutEndNL.txt");
        copyFile(src, dst, inputEncoding, outputEncoding, outputLineSeparator);

        src = new File("C:\\Users\\Dam\\Desktop\\testFiles\\testInEndEOF.txt");
        dst = new File("C:\\Users\\Dam\\Desktop\\testFiles\\testOutEndEOF.txt");
        copyFile(src, dst, inputEncoding, outputEncoding, outputLineSeparator);

    }

    private static void copyFile(File src, File dst, Charset inputEncoding, Charset outputEncoding, String outputLineSeparator) {
        try {
            String oldLineBreak = System.setProperty("line.separator", outputLineSeparator);
            BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(src), inputEncoding));
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(dst), outputEncoding));
            String line = reader.readLine();
            if(line != null) writer.write(line);
            while ((line = reader.readLine()) != null) {
                writer.newLine();
                writer.write(line);
            }
            reader.close();
            writer.close();
            System.setProperty("line.separator", oldLineBreak);
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }
}

Answer 1

The short answer is that you can't do it with .readLine(), because it strips off the end-of-line characters.

You will need to use .read() instead, which will read in character by character, and do your own EOL processing. This returns an int, but you can cast it to a char:

char c = (char)reader.read();

A CR/LF will come out as two separate characters, so you'll have to watch for that and process accordingly. If you know that your files will only have either CR/LF or just LF, then it's a little easier, because whenever you read a CR you know an LF is following straight behind.

The bytes you're reading won't vary. You'll be reading them as UTF-8 by default, which will always encode CR and LF as single byte characters. In int terms, they'll come out as 13 and 10 respectively.