In Java, how do I convert a byte array to a string of hex digits while keeping leading zeros?

Question

I'm working with some example java code for making md5 hashes. One part converts the results from bytes to a string of hex digits:

byte messageDigest[] = algorithm.digest();     
StringBuffer hexString = new StringBuffer();
for (int i=0;i<messageDigest.length;i++) {
    hexString.append(Integer.toHexString(0xFF & messageDigest[i]));
    }

However, it doesn't quite work since toHexString apparently drops off leading zeros. So, what's the simplest way to go from byte array to hex string that maintains the leading zeros?

Answer 1

Check out Hex.encodeHexString from Apache Commons Codec.

import org.apache.commons.codec.binary.Hex;

String hex = Hex.encodeHexString(bytes);