Customer loyalty is earned, never given.
过去从未死去,它甚至从未过去。
To understand a program you must become both the machine and the program.
The only way to do great work is to love what you do.
里氏替换原则是面向对象编程中的一个基本概念,它指出子类的对象应该能够替换超类的对象而不影响程序的正确性。