Java ConcurrentModificationException異常原因和解決方法

對Vector、ArrayList在迭代的時候如果同時對其進行增刪操作就會拋出java.util.ConcurrentModificationException異常

一、異常原因

代碼示例

public class ConcurrentModificationException {
    public static void main(String[] args) {
        function2();
        function1();
    }

    static void function1() {

        Person person1 = new Person();
        person1.setName("aa");
        person1.setAddress("AAA");
        Person person2 = new Person();
        person2.setName("bb");
        person2.setAddress("BBB");
        ArrayList<Person> persons = new ArrayList<>();
        persons.add(person1);
        persons.add(person2);
        System.out.println(persons.size());
        for (Person person : persons) {
            if ("AAA".equals(person.getAddress())) {
                persons.add(new Person("cc", "CCC"));
            }
            persons.remove(1);
        }
        System.out.println(persons.size());

    }

    static void function2() {

        ArrayList<Integer> list = new ArrayList<Integer>();
        list.add(2);
        list.add(3);
        System.out.println(list.size());
        Iterator<Integer> iterator = list.iterator();
        while (iterator.hasNext()) {
            Integer integer = iterator.next();
            if (integer == 2)
                list.remove(integer);
        }
        System.out.println(list.size());
    }
}

出現此異常的原因在於ArrayList的索引發生變化

二、解決

將ArrayList換成CopyOnWriteArrayList

    static void function2() {

        Person person1 = new Person();
        person1.setName("aa");
        person1.setAddress("AAA");
        Person person2 = new Person();
        person2.setName("bb");
        person2.setAddress("BBB");
        CopyOnWriteArrayList<Person> persons = new CopyOnWriteArrayList<>();
        persons.add(person1);
        persons.add(person2);
        System.out.println(persons.size());
        for (Person person : persons) {
            if ("AAA".equals(person.getAddress())) {
                persons.add(new Person("cc", "CCC"));
            }
            persons.remove(1);
        }
        System.out.println(persons.size());

    }

學習參考：https://www.cnblogs.com/dolphin0520/p/3933551.html