Ikk：新頁面: 11. class Alpha{ 12. public void foo(){System.out.print("Afoo ");} 13. } 14. public class Beta extends Alpha{ 15. public void foo(){System.out.print("Bfoo ");} 16. public s...

2013-03-30T06:06:59Z

新頁面: 11. class Alpha{ 12. public void foo(){System.out.print("Afoo ");} 13. } 14. public class Beta extends Alpha{ 15. public void foo(){System.out.print("Bfoo ");} 16. public s...

新頁面

11. class Alpha{
12. public void foo(){System.out.print("Afoo ");}
13. }
14. public class Beta extends Alpha{
15. public void foo(){System.out.print("Bfoo ");}
16. public static void main(String[] args){
17. Alpha a = new Beta();
18. Beta b = (Beta)a;
19. a.foo();
20. b.foo();
21. }
22. }

What is the result?
A. Afoo Afoo
B. Afoo Bfoo
C. Bfoo Afoo
D. Bfoo Bfoo
E. Compilation fails.
F. An exception is thrown at runtime.

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<span style="font-size:medium;">解答</span>

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<span style="font-size: medium;">Ans: D </span>

<span style="font-size:medium;"> 解說:
a和b皆指向同一個Beta型態的物件，以方法的多形來看都是叫用Beta中的foo方法
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{{SCJP 1.6版考題講解}}

SCJP 1.6版考題 084 - 修訂歷史

Ikk：新頁面: 11. class Alpha{ 12. public void foo(){System.out.print("Afoo ");} 13. } 14. public class Beta extends Alpha{ 15. public void foo(){System.out.print("Bfoo ");} 16. public s...