Posts
Tags
Friends
About
Guestbook 
package com.yanxizhu;

import java.util.*;

/**
 * @description: synchronizedList遍历错误
 * @date: 2022/3/19 11:30
 * @version: 1.0
 */
public class ConCurrentHashMapTest {

    public static void main(String[] args) {
        conCurrentDemo conCurrentDemo = new conCurrentDemo();
        for(int i=0;i<5;i++){
            new Thread(conCurrentDemo).start();
        }

    }

    public static class conCurrentDemo implements Runnable{

        //并发线程安全，修改报错
        private static List<String> list = Collections.synchronizedList(new ArrayList<>());

        static {
            list.add("apple");
            list.add("xiaomi");
            list.add("huawei");
        }

        @Override
        public void run() {
            Iterator<String> iterator = list.iterator();
            while(iterator.hasNext()){
                System.out.println(iterator.next());
                list.add("iphone");
            }
        }
    }
}

ThreadSafetyError：

Exception in thread "Thread-0" Exception in thread "Thread-3" Exception in thread "Thread-4" Exception in thread "Thread-2" Exception in thread "Thread-1" java.util.ConcurrentModificationException
	at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1043)
	at java.base/java.util.ArrayList$Itr.next(ArrayList.java:997)
	at com.yanxizhu.ConCurrentHashMapTest$conCurrentDemo.run(ConCurrentHashMapTest.java:35)
	at java.base/java.lang.Thread.run(Thread.java:834)
java.util.ConcurrentModificationException
	at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1043)
	at java.base/java.util.ArrayList$Itr.next(ArrayList.java:997)
	at com.yanxizhu.ConCurrentHashMapTest$conCurrentDemo.run(ConCurrentHashMapTest.java:35)
	at java.base/java.lang.Thread.run(Thread.java:834)

通过用CopyOnWriteArrayList修改：

package com.yanxizhu;

import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * @description: CopyOnWriteArrayList遍历集合
 * @date: 2022/3/19 11:30
 * @version: 1.0
 */
public class ConCurrentHashMapTest {

    public static void main(String[] args) {
        conCurrentDemo conCurrentDemo = new conCurrentDemo();
        for(int i=0;i<5;i++){
            new Thread(conCurrentDemo).start();
        }

    }

    public static class conCurrentDemo implements Runnable{

        //并发线程安全，修改报错
//        private static List<String> list = Collections.synchronizedList(new ArrayList<>());

        private static CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<>();

        static {
            list.add("apple");
            list.add("xiaomi");
            list.add("huawei");
        }

        @Override
        public void run() {
            Iterator<String> iterator = list.iterator();
            while(iterator.hasNext()){
                System.out.println(iterator.next());
                //CopyOnWriteArrayList，每次会重新复制一个新的，添加。
                list.add("iphone");
            }
        }
    }
}