code: public static final String base64Decode(String str) {
          if (str == null) {
              return null;
          } else {
              byte data[] = getBytes(str);
              return toString(base64Decode(data));
          }
      }
docs: Converts a base64 encoded String to a decoded String.
  
  @param str String, may be {@code null}.
  @return base64 encoded String {@code null} if the str was null.