四、方法重载，多态，重写综合练习

public class Demo

{

publicstatic void main(String[] args)

{

A a1 = new A();

A a2 = new B();

B b = new B();

C c = new C();

D d = new D();

System.out.println(a1.show(b));//1

System.out.println(a1.show(c));//2

System.out.println(a1.show(d));//3

System.out.println(a2.show(b));//4

System.out.println(a2.show(c));//5

System.out.println(a2.show(d));//6

System.out.println(b.show(b));//7

System.out.println(b.show(c));//8

System.out.println(b.show(d));//9

}

}

class A

{

public String show(D obj)

{

return ("A and D");

}

public String show(A obj)

{

return ("A and A");

}

}

class B extends A

{

public String show(B obj)

{

return("B and B");

}

public String show(A obj)

{

return ("B and A");

}

}

class C extends B{}

class D extends B{}

答案：   关键点 调用的时候先去父类中找到方法，然后再去子类中找到子类重写的方法

①  A and A

②  A and A

③  A and D

④  B and A        //先去父类找这个参数对应的重载的方法，然后再去子类中找到重写的方法

⑤  B and A

⑥  A and D

⑦  B and B       //优先调用实参与形参的继承树近的方法

⑧  B and B

⑨  A and D