The Liskov Substitution Principle is a fundamental concept in object-oriented programming, stating that objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program.

解释：乌鸦聚集在一起，虽然看上去很和好，实际上并不亲密；不慎重地结交朋友，虽似牢固，终必破裂。

痛苦是暂时的，但音乐是永恒的。