唯有在存取集合之前，将所有执行绪都锁定物件，同步处理才会有效。

Synchronization is effective only if all threads lock the object before accessing the collection.

youdao

此方法的默认实现需要由派生类重写，以便在清除集合之前执行某些操作。

The default implementation of this method is intended to be overridden by a derived class to perform some action before the collection is cleared.

youdao

在创建使用应用程序对象和资源集合的规则之前请记住这一点。

Keep this in mind before you create rules that use your application objects and resource collections.

youdao

And that does two things: bug one, it helps catch bugs in your code, and secondly it often converts it into a more efficient sequence of instructions before you actually go off and run it. All right?

这有两点好处：,第一是可以帮助你发现程序中的，第二是把你的代码,在运行之前,转换为更有效率的指令的集合，对不对？

麻省理工公开课 - 计算机科学及编程导论课程节选