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();
            }
        }
    }