code: public static <T> Class<T> unwrap(Class<T> type) {
          if (type == null) {
              throw new IllegalArgumentException();
          }
  
          Class<T> unwrapped = (Class<T>) WRAP_TO_PRIMITIVE.get(type);
          return (unwrapped == null) ? type : unwrapped;
      }
docs: Guava unwrap alternative.
  
  @param type type
  @return unwrapped result