Java MD5 function: can someone explain me this code?

Question

I've found this java function that encrypt a string in MD5, but I fail to understand how it works:

public static String makeMD5(String text){
    MessageDigest md;
    try {
        md = MessageDigest.getInstance("MD5");

        md.update(text.getBytes());
        byte byteData[] = md.digest();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < byteData.length; i++)
            sb.append(Integer.toString((byteData[i] & 0xff) + 0x100, 16).substring(1));

        text = sb.toString();
        return text;
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
        return null;
    }
}

I don't understand the line just after the for loop..

Thanks a lot!

`text = sb.toString();` converts `StringBuffer` object to its `String` representation. — PM 77-1, Nov 17 '15 at 21:35
For more info go to [link](http://docs.oracle.com/javase/7/docs/api/java/lang/StringBuffer.html) — Abdelhak, Nov 17 '15 at 21:35

score 0 · Accepted Answer · edited May 23 '17 at 10:28

The line after the for loop is a frankly overcomplicated way to convert a byte array into hexadecimal. An equivalent, simpler approach might be

sb.append(String.format("%02x", b & 0xff));

though if you can use third-party libraries there are even simpler solutions. How to convert a byte array to a hex string in Java? has a number of suggestions.

(If third party libraries are available, Guava will let you do this whole method in the one line Hashing.md5().hashString(text, Charset.defaultCharset()).toString().)

Java MD5 function: can someone explain me this code?

1 Answers1