檢視 SCJP 1.6版考題 212 的原始碼

Given: 
<br>3. &nbsp;import java.util.*; 
<br>4. &nbsp; public class Hancock{ 
<br>5. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;//insert code here 
<br>6. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;list.add("foo"); 
<br>7. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } <br>8. &nbsp;} 

<br>Which two code fragments, inserted independently at line 5, will compile without warnings? (Choose two.) <br>&nbsp; A. public void addStrings(List list){ 
<br>&nbsp; B. public void addStrings(List&lt;String&gt; list){ 
<br>&nbsp; C. public void addStrings(List&lt;? super String&gt; list){ 
<br>&nbsp; D. public void addStrings(List&lt;? extends String&gt; list){ &nbsp;
 

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

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

<span style="font-size:medium;"> 解說:
&nbsp;List的add方法參數是Object型態 &nbsp;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;可以是Object型態以下各種型態 <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;只要是泛型操作，都要指定型態，A就不行 <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;D限定String及其子類別型態不符合可以代入Object(任何型態)的宣告 
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