在能源价格低廉的年代，房屋建筑商并不太担心未密封的裂缝。
Back in the days when energy was cheap, home builders didn't worry much about unsealed cracks.
描述未密封类的设计准则。
即使没有附加扩展性机制，未密封类在许多开发方案中也非常有用。
An unsealed class can be useful in many development scenarios, even without the additional extensibility mechanisms.
应用推荐