大家都搜：
并发异常
1、It implements List and is thread-safe, but its iterators will not throw ConcurrentModificationException and do not require any additional locking during traversal.───它实现了List，而且是线程安全的，但是它的迭代器不会抛出ConcurrentModificationException，遍历期间也不要求额外的锁定。