API and implementation is not separated entirely in conventional Object-Oriented system. The degree of coupling between API and user program is high,so the maintenance and upgrade of the system will become difficult.

• 传统的面向对象系统应用编程接口与实现分离不彻底,接口类的部分实现细节仍然与用户程序过紧地耦合在一起,使系统的维护和升级变得困难。