4、Animal是一个抽象类,有两个子类Dog和Cat继承Animal针对实现的编程是: Cat c = new Cat(); c.meow(); //猫叫的方式 Dog d = new Dog(); d.bark(); //狗叫的方式针对接口的编程是: Animal a = new Dog(); a.makeSound(); //makeSound中会调用bark(); Animal a = new Cat(); a.makeSound(); //makeSound中会调用meow(); 3.多用组合,少用继承根据读headfirst策略模式做的c#