static Type getSuperclassTypeParameter(Class<?> subclass)

{
    Type superclass = subclass.getGenericSuperclass();
    if (superclass instanceof Class)
    {
        throw new RuntimeException("Missing type parameter.");
    }
    ParameterizedType parameterized = (ParameterizedType) superclass;
    return $Gson$Types.canonicalize(parameterized.getActualTypeArguments()[0]);
}

这里if (superclass instanceof Class)是什么意思？