有关高并发下List的问题以及高并发下如何使用List

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.UUID;
import java.util.concurrent.CopyOnWriteArrayList;
/**
 * @author :yanjun.hou
 * @description :
 * @create :2022-04-17 20:23:00
 */
public class ListTest {
    //普通list---会产生多线程操作的时候大小不是设想的 可能会减少
    static List<String> nomalList = new ArrayList<>();
    //使用集合工具类 转换list
    static List<String> colList = Collections.synchronizedList(new ArrayList<>());
    //可读写的list  推荐使用
    static List<String> copyOnWriteList = new CopyOnWriteArrayList<>();
    /**
     * 测试高并发下 List使用
     */
    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(new TestList());
        Thread t2 = new Thread(new TestList());
        
        t1.start();
        t2.start();
        
        t1.join();
        t2.join();
        
        System.out.println("【nomalList】:"+nomalList.size());
        System.out.println("【colList】:"+colList.size());
        System.out.println("【copyOnWriteList】:"+copyOnWriteList.size());
    }
    public static class TestList implements Runnable {
        @Override
        public void run() {
            for (int i = 0; i < 3000; i++) {
                nomalList.add(UUID.randomUUID().toString().substring(0, 5));
                colList.add(UUID.randomUUID().toString().substring(0, 5));
                copyOnWriteList.add(UUID.randomUUID().toString().substring(0, 5));
            }
        }
    }
}

可以看出，普通List在多线程的情况下，会出现大小小与预期的情况。