code: private String encryptPassword(String password)
              throws AuthenticationException {
          byte[] passwordBytes = password.getBytes();
  
          try {
              MessageDigest algorithm = MessageDigest.getInstance("MD5");
              algorithm.reset();
              algorithm.update(passwordBytes);
  
              byte messageDigest[] = algorithm.digest();
              BigInteger number = new BigInteger(1, messageDigest);
  
              password = number.toString(16);
              if (password.length() == 31) {
                  password = "0" + password;
              }
          } catch (Exception e) {
              throw new AuthenticationException(
                      "Internal password encryption failure: " + e.getMessage());
          }
          return password;
      }
docs: Password encryption method
  
  @param password Password to be encrypted
  @return encrypted password
  @throws AuthenticationException if fail to encrypt