集合类线程不安全

集合类不安全

1.ArrayList

import java.util.*; import java.util.concurrent.CopyOnWriteArrayList; //ConcurrentModificationException并发修改异常 public class ListTest { public static void main(String[] args) { //并发下ArrayList安全吗？ //List list=new Vector<>(); //List list= Collections.synchronizedList(new ArrayList<>()); List list=new CopyOnWriteArrayList<>(); for (int i = 0; i < 10; i++) { new Thread(()->{ list.add(UUID.randomUUID().toString().substring(0,5)); System.out.println(list); },String.valueOf(i)).start(); } } }

2.HashSet

import java.util.Collections; import java.util.HashSet; import java.util.Set; import java.util.UUID; import java.util.concurrent.CopyOnWriteArraySet; //ConcurrentModificationException:并发修改异常 public class HashSetTest { public static void main(String[] args) { //HashSet set = new HashSet<>(); Set set=new CopyOnWriteArraySet<>(); for (int i = 0; i < 30; i++) { new Thread(()->{ set.add(UUID.randomUUID().toString().substring(0,5)); System.out.println(set); },String.valueOf(i)).start(); } } }

3.HashMap

import java.util.HashMap; import java.util.Map; import java.util.UUID; import java.util.concurrent.ConcurrentHashMap; //ConcurrentModificationException:并发修改异常 public class HashMapTest { public static void main(String[] args) { //线程不安全 //Map map=new HashMap<>(); Map map= new ConcurrentHashMap<>(); for (int i = 0; i < 30; i++) { new Thread(()->{ map.put(Thread.currentThread().getName(), UUID.randomUUID().toString().substring(0,5)); System.out.println(map); },String.valueOf(i)).start(); } } }