List
     
       list =new ArrayList
      
       ();        list.add("boss");        list.add("good");        list.add("No");        list.add("Fine");        System.out.println(list);//[boss, good, No, Fine]        Collections.sort(list);        System.out.println(list);//[Fine, No, boss, good]        list.add("我们");        list.add("你就是");        list.add("他很调");        list.add("明天见");        int i=0;        while(true){                for (String dwonCountCmd : list) {                            if (i<30) {                    System.out.println(dwonCountCmd+i);                    i++;                } else{//在循环中把集合的一个元素移除了，如果此时不break的话，就会报错                    list.remove(dwonCountCmd);                    System.out.println(list.toString());                    break;                }            }        }
      
     

 

 

会报这种错

Exception in thread "main" java.util.ConcurrentModificationException    at java.util.AbstractList$Itr.checkForComodification(Unknown Source)    at java.util.AbstractList$Itr.next(Unknown Source)    at Test2.main(Test2.java:47)