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

A simple approach would be to check how many digits are output by Integer.toHexString() and add a leading zero to each byte if needed. Something like this:

public static String toHexString(byte[] bytes) {     StringBuilder hexString = new StringBuilder();      for (int i = 0; i < bytes.length; i++) {         String hex = Integer.toHexString(0xFF & bytes[i]);         if (hex.length() == 1) {             hexString.append('0');         }         hexString.append(hex);     }      return hexString.toString(); }