JAVA题目下面CE为什么不对~~求解释~~~10.abstractclassA{11.abstractvoida1();12.voida2(){}13.}14.classBextendsA{15.voida1(){}16.voida2(){}17.}18.classCextendsB{voidc1(){}}and:Ax=newB();Cy=newC();Az=newC()

Question

JAVA题目 下面CE为什么不对~~求解释~~~
10. abstract class A{
11. abstract void a1();
12. void a2(){}
13. }
14. class B extends A{
15. void a1(){}
16. void a2(){}
17. }
18. class C extends B{void c1(){}}
and:
A x = new B(); C y = new C(); A z = new C();
What are four valid examples of polymorphic method calls? (Choose four.)
A. x.a2();
B. z.a2();
C. z.c1();
D. z.a1();
E. y.c1();
F. x.a1();

Answer 1

C 因为z是 A A没有c1()方法。
E 应该是因为y.c1()不是个多态的方法。