List.iterator() 是线程安全的吗?
在 Java 中:List.iterator() 是线程安全的，即返回的迭代器是否反映了列表在任何时候的当前状态，或者只是列表在其时的状态创作?
In Java: Is List.iterator() thread-safe, i.e. does the returned iterator reflect the current state of the list at any time or just the state of the list at the time of its creation?
推荐答案
List.iterator() 的行为未定义或与不同的 List 实现一致.
The behaviour of List.iterator() is not defined or consistent with different List implementations.
对于 ArrayList、LinkedList，如果在迭代列表时修改了列表，则可能会得到 ConcurrentModificationException.(不能保证)避免此问题的方法是使用 synchronizedList() 并在迭代列表时锁定列表.
For ArrayList, LinkedList, you can get a ConcurrentModificationException if the list is modified when you are iterating over it. (This is not guaranteed) The way to avoid this issue is to use a synchronizedList() and lock the list while iterating over it.
对于 Vector，集合是同步的，但迭代器不是线程安全的.
For Vector, the collection is synchronized, but the iterator is not thread safe.
对于 CopyOnWriteArrayList，您在调用 iterator() 时会获得列表中元素的快照，此迭代器是线程安全的，您不需要使用任何锁定.注意:元素的内容可以改变.
For CopyOnWriteArrayList, you get a snapshot of the elements in the list at the time you call iterator(), This iterator is thread safe, and you don't need to use any locking. Note: the contents of the elements can change.
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