绕过泛型，通过反射把 String 添加到 List < Integer > 中

public class ArrayListDemo {

public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
    List<Integer> list = new ArrayList<Integer>();

    list.add(1);
    // list.add("hello");不能添加
  
    Class clzz = list.getClass();
    Method method = clzz.getMethod("add",Object.class);
    method.invoke(list,"hello");

    System.out.println(list);
}

}