code: public static String encode(String password, String algorithm) {
      byte[] unencodedPassword = password.getBytes();
      MessageDigest md = null;
      try {
        // first create an instance, given the provider
        md = MessageDigest.getInstance(algorithm);
      } catch (Exception e) {
        logger.error("Exception:{}", e);
        return password;
      }
  
      md.reset();
      // call the update method one or more times
      // (useful when you don't know the size of your data, eg. stream)
      md.update(unencodedPassword);
      // now calculate the hash
      byte[] encodedPassword = md.digest();
      StringBuilder buf = new StringBuilder();
      for (int i = 0; i < encodedPassword.length; i++) {
        if ((encodedPassword[i] & 0xff) < 0x10) buf.append("0");
        buf.append(Long.toString(encodedPassword[i] & 0xff, 16));
      }
      return buf.toString();
    }
docs: Encode a string using algorithm specified in web.xml and return the
  resulting encrypted password. If exception, the plain credentials string
  is returned
  
  @param password passord string
  @param algorithm Algorithm used to do the digest
  @return encypted password based on the algorithm.