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SCJP 1.6版考題 058 - 修訂歷史
2026-05-01T02:24:10Z
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Ikk：新頁面: 10. interface Foo{} 11. class Alpha implements Foo{} 12. class Beta extends Alpha{} 13. class Delta extends Beta{ 14. public static void main(String[] args){ 15. Beta x = n...
2013-03-30T07:05:34Z
<p>新頁面: 10. interface Foo{} 11. class Alpha implements Foo{} 12. class Beta extends Alpha{} 13. class Delta extends Beta{ 14. public static void main(String[] args){ 15. Beta x = n...</p>
<p><b>新頁面</b></p><div> 10. interface Foo{}<br />
11. class Alpha implements Foo{}<br />
12. class Beta extends Alpha{}<br />
13. class Delta extends Beta{<br />
14. public static void main(String[] args){<br />
15. Beta x = new Beta();<br />
16. //insert code here<br />
17. }<br />
18. }<br />
<br />
<br />
Which code, inserted at line 16, will cause a java.lang.ClassCastException?<br />
A. Alpha a = x;<br />
B. Foo f = (Delta)x;<br />
C. Foo f = (Alpha)x;<br />
D. Beta b = (Beta)(Alpha)x;<br />
<br />
<div class="toccolours mw-collapsible mw-collapsed"><br />
<span style="font-size:medium;">解答</span><br />
<br />
----<br />
<div class="mw-collapsible-content"><br />
<span style="font-size: medium;">Ans: B </span><br />
<br />
<span style="font-size:medium;"> 解說:<br />
x物件是Beta型態，不能向下轉型為其子類別Delta型態。在執行時會發生java.lang.ClassCastException<br />
</span> <br />
</div></div><br />
{{SCJP 1.6版考題講解}}</div>
Ikk