code: public static long refSizeOf(Class<?> clz) {
      if (PrimitiveTypeUtil.isPrimitive(clz)) {
        return PrimitiveTypeUtil.sizeOf(clz);
      } else {
        return refSize();
      }
    }
docs: Get the size of reference.(considered UseCompressedOops)<br>
  If the class is primitive type, return it's actual size.
  
  @param clz
  @return