CopyOnWriteArrayList

CopyOnWriteArrayList

ArrayList是多线程不安全的，建议使用CopyOnWriteArrayList

package com.example.juc;

import java.util.List;
import java.util.UUID;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * ArrayList多线程不安全，解决方法
 * 1.Vector 效率不高，Vector.add底层是用synchronized实现的
 * 2.Collections.synchronizedList 顾名思义，底层也是用synchronized实现的
 * 3.CopyOnWriteArrayList 写入时复制，底层是用Lock实现的
 */
public class TestList {
    public static void main(String[] args) {
//        List<String> list = new ArrayList<>();
//        List<String> list = new Vector<>();
//        List<String> list = Collections.synchronizedList(new ArrayList<>());
        List<String> list = new CopyOnWriteArrayList<>();
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                list.add(UUID.randomUUID().toString().substring(0, 5));
                System.out.println(list);
            }, "" + i).start();

        }
    }
}