code: public static boolean isAlphabetic(String s) {
          if (isEmpty(s)) return defaultEmptyOK;
  
          // Search through string's characters one by one
          // until we find a non-alphabetic character.
          // When we do, return false; if we don't, return true.
          for (int i = 0; i < s.length(); i++) {
              // Check that current character is letter.
              char c = s.charAt(i);
  
              if (!isLetter(c))
                  return false;
          }
  
          // All characters are letters.
          return true;
      }
docs: Returns true if string s is letters only.
  
  NOTE: This should handle i18n version to support European characters, etc.
  since it now uses Character.isLetter()