OS.1.2. ReverseByteStream

//OS_HW01_2 161514 17/18

import java.io.*;

public class OS_HW01_2 {
    public static void main(String[] args) throws IOException {
//        File dir = new File(System.getProperty("user.dir"));
        String pathRead = "src/texts/source.txt";
        String pathWrite = "src/texts/destination.txt";
//        File source = new File(pathRead);
//        source.mkdirs();      //this makes a dir, not a txt file
//        File destination = new File(pathWrite);
//        destination.mkdirs(); //this makes a dir, not a txt file

        BufferedInputStream in = new BufferedInputStream(new FileInputStream(pathRead));
        PrintStream out = new PrintStream(new BufferedOutputStream(new FileOutputStream(pathWrite)));

        copyStreamReversed(in, out);
    }
    public static void copyStreamReversed(InputStream in, OutputStream out)
            throws IOException {
        try {
//            int c;
            byte[] buffer = new byte[100];
//            while ((c = in.read()) != -1)
//                ;
            in.read(buffer);
            reverse(buffer);
            out.write(buffer);  //ask why?
        } finally {
            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
        }
    }
    public static void reverse(byte[] arr) {
        if (arr == null) {
            return;
        }
        int i = 0;
        int j = arr.length - 1;
        byte tmp;
        while (j > i) {
            tmp = arr[j];
            arr[j] = arr[i];
            arr[i] = tmp;
            j--;
            i++;
        }
    }
}