Java 多态性 vs 覆盖 vs 重载

发布于10月01日

就Java而言，当有人问:

什么是多态性？

overloading或overriding是可以接受的答案吗？

我想还有比这更重要的一点.

IF you had a abstract base class that defined a method with no implementation, and you defined that method in the sub class, is that still overridding?

我认为overloading肯定不是正确的答案.

推荐答案

表达多态性的最清晰方式是通过抽象基类(或接口)

public abstract class Human{
   ...
   public abstract void goPee();
}

This class is abstract because the goPee() method is not definable for Humans. It is only definable for the subclasses Male 和 Female. Also, Human is an abstract concept — You cannot create a human that is neither Male nor Female. It’s got to be one or the other.

因此，我们通过使用抽象类来推迟实现.

public class Male extends Human{
...
    @Override
    public void goPee(){
        System.out.println("St和 Up");
    }
}

和

public class Female extends Human{
...
    @Override
    public void goPee(){
        System.out.println("Sit Down");
    }
}

现在我们可以告诉一整间屋子的人go 小便.

public static void main(String[] args){
    ArrayList<Human> group = new ArrayList<Human>();
    group.add(new Male());
    group.add(new Female());
    // ... add more...

    // tell the class to take a pee break
    for (Human person : group) person.goPee();
}

运行此命令将产生以下结果: