关于iterator迭代器是fail-fast机制

没弄清楚到底是结构发生改变还是元素改变抛出异常
故做以下验证

public static void main(String[] args) {
     
        Person p1 = new Person(10, "xl");
        Person p2 = new Person(11, "xm");
        Person p3 = new Person(12, "xs");
        List<Person> personList = new LinkedList<>();
        personList.add(p1);
        personList.add(p2);
        personList.add(p3);
        Iterator<Person> iterator = personList.iterator();
        int i = 0;
        while (iterator.hasNext()){
     
            if (i==2){
     
                personList.get(i).age++;
            }
            System.out.println(iterator.next());
            i++;
        }
    }

    public static class Person{
     
        public int age;
        public String name;

        public Person(int age, String name) {
     
            this.age = age;
            this.name = name;
        }

        @Override
        public String toString() {
     
            return "Person{" +
                    "age=" + age +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

如上代码是可以成功跑出来的

但如果改成这样

则会抛出异常

所以证明了只有在结构改变的情况 下才会触发fail fast机制