线程不安全的ArrayList

最新推荐文章于 2025-09-05 20:08:02 发布

原创最新推荐文章于 2025-09-05 20:08:02 发布 · 1.7k 阅读

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文章标签：

#arraylist #线程 #线程安全

本文通过示例代码展示了当多个线程同时对java.util.ArrayList进行读写操作时，可能会抛出java.util.ConcurrentModificationException异常。文章提供了具体的实现代码并解释了如何复现此问题。

概述

java.util.ArrayList不是线程安全的，当有多个线程并发读写ArrayList的时候，ArrayList会抛出如下异常

java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819)
    at java.util.ArrayList$Itr.next(ArrayList.java:791)

代码演示

import java.util.List;

public class ReadThread implements Runnable{
    private List<String> list ;
    public ReadThread(List<String> list) {
        this.list = list;
    }

    @Override
    public void run() {
      for(String ele : list) {
          System.out.println(ele);
      }
    }
}

import java.util.List;

public class WriteThread implements Runnable{
    private List<String> list ;
    public WriteThread(List<String> list) {
        this.list = list;
    }

    @Override
    public void run() {
      this.list.add("11");
    }
}

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ArrayListConCurrentWriteReadTest {

    private void test() {
        //1、准备数据
        List<String> list = new ArrayList<>();
        list.add("1");
        list.add("2");
        list.add("3");
        list.add("4");
        list.add("5");

        //2、模拟多线程对list进行读和写
        ExecutorService executorService = Executors.newFixedThreadPool(5);
        for (int i = 0; i < 5; i++) {
            executorService.execute(new ReadThread(list));
            executorService.execute(new WriteThread(list));
        }
    }


    public static void main(String[] args) {
        new ArrayListConCurrentWriteReadTest().test();
    }
}