Unwanted code

Question

Hi,
Please run my simple program below and save the mac key in a named file you like where you will see the mac key with some weird code in the beginning. If I print the mac key directly to screen, it will be fine. Please help.
import java.io.*;
import java.security.*;
import javax.crypto.*;
public class GenMacKey {
static String MAC_TYPE = "HmacMD5";
public static void main(String[] args) throws Exception {
if (args.length != 1) {
throw (new IllegalArgumentException("md5: md5 <string>"));
try {
// Generate secret key for HMAC-MD5
KeyGenerator kg = KeyGenerator.getInstance(MAC_TYPE);
SecretKey sk = kg.generateKey();
// Get instance of Mac object implementing HMAC-MD5, and
// initialize it with the above secret key
Mac mac = Mac.getInstance(MAC_TYPE);
mac.init(sk);
//System.out.println(bytesToHexString(mac.doFinal()));
ObjectOutputStream oos = new ObjectOutputStream(
     new FileOutputStream(args[0]));
oos.writeObject(bytesToHexString(mac.doFinal()));
oos.close();
catch (NoSuchAlgorithmException e) {
e.printStackTrace();
catch (InvalidKeyException e) {
e.printStackTrace();
public static String bytesToHexString(byte[] buf){
StringBuffer sb= new StringBuffer(buf.length *2);
for (int i=0; i < buf.length; i++){
int v = buf[i] & 0xff;
if (v<16){
sb.append('0');
sb.append(Integer.toHexString(v));
return sb.toString().toLowerCase();
}

Answer 1

Thanks for that and any suggestion ?
I have tried writeByte or writeBytes but in failure.Why are you writing an object? All you need is a FileWriter then you can use the Writer.write(String str) method!