The idea of reworking your code to improve its maintainability without changing its observable behavior is not new.
修改代码使其易于维护，要求不能修改程序可观察的行为，这个思想并不是全新的理念。
The idea of reworking your code to improve its maintainability without changing its observable behavior is not new.
修改代码使其易于维护，要求不能修改程序可观察的行为，这个思想并不是全新的理念。
应用推荐