集合和Map线程安全问题解决

1.ArrayList线程不安全（没有加可重入锁）
解决方法 Vector(synchronized)  Collections(synchronized) CopyOnWriteArrayList(ReentrantLock)

2.HashSet——》CopyOnWriteArraySet

3.HashMapt——》ConcurrentHashMap

package juc.two;

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

/**
 * ArrayList线程不安全（没有加可重入锁）
 * 解决方法 Vector(synchronized)  Collections(synchronized) CopyOnWriteArrayList(ReentrantLock)
 */

public class ThreadDemo4 {
    public static void main(String[] args) {
        //创建ArrayList集合
        //List<String> list = new ArrayList<>();
        //Vector解决
        //List<String> list = new Vector<>();
        //Collections解决
        //List<String> list = Collections.synchronizedList(new ArrayList<>());
        //CopyOnWriteArrayList解决
        //List<String> list = new CopyOnWriteArrayList<>();

        /*for(int i = 0; i<30; i++){
            new Thread(()->{
                //向集合添加内容
                list.add(UUID.randomUUID().toString().substring(0,8));
                //从集合获取内容
                System.out.println(list);
            },String.valueOf(i)).start();
        }*/

        //演示HashSet
        //Set<String> set = new HashSet<>();

        //Set<String> set = new CopyOnWriteArraySet<>();

        /*for(int i = 0; i<30; i++){
            new Thread(()->{
                //向集合添加内容
                set.add(UUID.randomUUID().toString().substring(0,8));
                //从集合获取内容
                System.out.println(set);
            },String.valueOf(i)).start();
        }*/

        //演示HashMap
        //Map<String,String> map = new HashMap<>();

        Map<String,String> map = new ConcurrentHashMap<>();

        for(int i = 0; i<30; i++){
            String key = String.valueOf(i);
            new Thread(()->{
                //向集合添加内容
                map.put(key,UUID.randomUUID().toString().substring(0,8));
                //从集合获取内容
                System.out.println(map);
            },String.valueOf(i)).start();
        }
    }
}