How to write new line characters into a file in Java after converting a Byte Array into a String

Question

I want to read a text file, convert it into a byte array, process the byte array and then write it into another file. To do so I don't want to lose any newline characters so that new lines shall also be written into the new file created in the previous step. This is what I have done so far:

StringBuilder line=null;
            try (BufferedReader in = new BufferedReader(new FileReader(filePath))) {
                line = new StringBuilder();
                String tempLine=null;
                fileSelect=true;
                while ((tempLine=in.readLine()) != null) {                      
                    line.append(tempLine+System.lineSeparator());
                }
            }

          byte[] plaintext =String.valueOf(line).getBytes("UTF-8");

    // Encrypt the data
          byte[] encrypted = cipher.doFinal(plaintext);
          //String enc=new String(encrypted);

          try (FileOutputStream out = new FileOutputStream(fileName)) {
                out.write(encrypted);
            }

Take filePath and fileName as valid identifiers in the above code snippet.

Do you want to encrypt every line in the file seperatly, except newline characters? — Chriss
– Chriss, Commented Mar 28, 2014 at 8:44

Harmlezz · Accepted Answer · 2014-03-28 08:49:24Z

2

I do not understand why you do convert the string, composed using the StringBuilder, into a byte array, but nevertheless, try this code:

String text = "hallo!\n" + "How do\n" + "you do?\n";
System.out.println("Before conversion:");
System.out.print(text);
ByteArrayInputStream is = new ByteArrayInputStream(text.getBytes(Charset.forName("UTF-8")));
StringBuilder builder = new StringBuilder();
try (BufferedReader in = new BufferedReader(new InputStreamReader(is))) {
    String line;
    while ((line = in.readLine()) != null) builder.append(line + lineSeparator());
}
byte[] bytes = builder.toString().getBytes(Charset.forName("UTF-8"));
System.out.println("After conversion:");
System.out.print(new String(bytes, "UTF-8"));

OUTPUT:

Before conversion:
hallo!
How do
you do?

After conversion:
hallo!
How do
you do?

answered Mar 28, 2014 at 8:49

Harmlezz

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3 Comments

DecodingLife Over a year ago

I want to write that into a file and not just print it on the console. In your case, I want 'line' to be written into a text file(say) with all the new lines on their appropriate positions. @harmlezz

Harmlezz Over a year ago

my code is an example how to do it. I use the console but you may do exactly the same for your file. Just use the proper encoding as I did in each step. Shouldn't be to hard for you now, right?

DecodingLife Over a year ago

yeah, hope so. But I am getting problem only with writing onto the file. Will turn up if I still face the same problem using ByteArrayOutputStream for writing into the file. - @harmlezz

Michele Mariotti · Accepted Answer · 2014-03-28 09:24:08Z

0

it makes no sense write encrypted lines directly as bytes and use CRLF as separator, because CRLF is a legit byte sequence for encrypted data.

you also need to encode every single encrypted line in a compatible format, such as Base64:

public static void main(String[] args) throws IOException
{
    File source = new File("path/to/source/file");
    File target = new File("path/to/target/file");

    List<String> lines = FileUtils.readLines(source, "UTF-8");

    for(String line : lines)
    {
        byte[] encrypted = someEncryptionMethod(line.getBytes("UTF-8"));

        String base64 = Base64.encodeBase64String(encrypted);

        FileUtils.write(target, base64 + "\r\n", true);
    }

}

UPDATE

based only on what you are asking, this is what you should expect:

File source = new File("path/to/source/file");
File target = new File("path/to/target/file");

byte[] bytes = FileUtils.readFileToByteArray(source);

byte[] bytes2 = process(bytes);

FileUtils.writeByteArrayToFile(target, bytes2);

edited Mar 28, 2014 at 9:24

answered Mar 28, 2014 at 8:49

Michele Mariotti

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8 Comments

DecodingLife Over a year ago

I am implementing CBC in Java and in CBC you need to have entire plaintext message and then fed them to appropriate library function to process for encryption. @michele

Michele Mariotti Over a year ago

-1, this is not what your question states. Correct your question and i'll remove downvote, and try to answer if i can.

DecodingLife Over a year ago

My question is just about file handling and nothing more or less than that. I am not talking about encryption or any thing whatsoever. -@michele

Michele Mariotti Over a year ago

ok edited my answer (edit your question anyway because i can't remove downvote otherwise)

DecodingLife Over a year ago

I dont understand why you sticking with the encryption thing. Encryption doesn't matters at all here, why should I edit my question? My question says what I want to do. I don't want anybody here to care for what encryption/decryption I use. -@michele

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