https://fgchen.com/wiki/index.php?action=history&feed=atom&title=SCJP_1.6%E7%89%88%E8%80%83%E9%A1%8C_199SCJP 1.6版考題 199 - 修訂歷史2026-05-04T18:42:07Z本 Wiki 上此頁面的修訂歷史MediaWiki 1.29.0https://fgchen.com/wiki/index.php?title=SCJP_1.6%E7%89%88%E8%80%83%E9%A1%8C_199&diff=1213&oldid=prevIkk：新頁面: Given: 10. interface A{void x();} 11. class B implements A{public void x(){} public void y(){}} 12. class C extends B{public void x(){}} And: 20. java.util.List<A> list = new jav...2013-03-30T00:13:56Z<p>新頁面: Given: 10. interface A{void x();} 11. class B implements A{public void x(){} public void y(){}} 12. class C extends B{public void x(){}} And: 20. java.util.List<A> list = new jav...</p>
<p><b>新頁面</b></p><div> Given:<br />
10. interface A{void x();}<br />
11. class B implements A{public void x(){} public void y(){}}<br />
12. class C extends B{public void x(){}}<br />
And:<br />
20. java.util.List<A> list = new java.util.ArrayList<A>();<br />
21. list.add(new B());<br />
22. list.add(new C());<br />
23. for(A a : list){<br />
24. a.x();<br />
25. a.y();<br />
26. }<br />
<br />
What is the result?<br />
<br />
A. The code runs with no output.<br />
B. An exception is thrown at runtime.<br />
C. Compilation fails because of an error in line 20.<br />
D. Compilation fails because of an error in line 21.<br />
E. Compilation fails because of an error in line 23.<br />
F. Compilation fails because of an error in line 25.<br />
<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: F </span><br />
<br />
<span style="font-size:medium;"> 解說:<br />
<BR><br />
25行出錯是因為取出來的a是A型態，A型態沒有y方法，無法通過編譯器檢查，改法如下：<br />
interface A{void x(); void y(); }<br />
class B implements A{public void x(){} public void y(){}}<br />
class C extends B{public void x(){}}<br />
class test {<br />
public static void main(String[] args){<br />
java.util.List<A> list = new java.util.ArrayList<A>();<br />
list.add(new B());<br />
list.add(new C()); <br />
for(A a : list){<br />
a.x();<br />
a.y();<br />
}<br />
}<br />
}<br />
<br />
</span> <br />
</div></div><br />
{{SCJP 1.6版考題講解}}</div>Ikk