code: public static String unpackString(Object obj) {
          Object value = unpack(obj);
          return value == null ? null : value.toString();
      }
docs: Unpacks the given object to its {@code String}
  value.  Same behavior as the other {@code unpack}
  method ending with a call to {@code toString()}.
  @param obj the value to unpack
  @return the unpacked string value
  @see ObjectUtil#unpack(Object)