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    public static void main(String[] args) {

        List<String> stringList = Arrays.asList("A", "B");
        List<Integer> integerList = Arrays.asList(1, 2);

        List<? extends List<? extends Serializable>> listList = Arrays.asList(stringList, integerList);

        List<?> list = listList.get(0);

        Type type = ((ParameterizedType) list.getClass().getGenericSuperclass()).getActualTypeArguments()[0];
        Class clazz = (Class) type;

    }