檢視 SCJP 1.6版考題 209 的原始碼

Given: 
<br>1. &nbsp; import java.util.*; 
<br>2. &nbsp; public class TestSet{ 
<br>3. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; enum Example{ONE, TWO, THREE} 
<br>4. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; public static void main(String[] args){ 
<br>5. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Collection coll = new ArrayList(); 
<br>6. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;coll.add(Example.THREE); <br>7. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;coll.add(Example.THREE); <br>8. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;coll.add(Example.THREE); <br>9. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;coll.add(Example.TWO); <br>10. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;coll.add(Example.TWO); 
<br>11. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;coll.add(Example.ONE) 
<br>12. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Set set = new HashSet(coll); <br>13. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;} <br>14. &nbsp; } 
<br>Which statement is true about the set variable on line 12? 那一個敘述對於第12行的set變數為正確？ 
<br> <br>&nbsp; A. The set variable contains all six elements from the coll collection, and the order is guaranteed to be preserved. 
<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;set變數包含6個從coll來的元素，且保證其排序的特性。 

<br>&nbsp; B. The set variable contains only three elements from the coll collection, and the order is guaranteed to be preserved. <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;set變數包含3個從coll來的元素，且保證其排序的特性。 

<br>&nbsp; C. The set variable contains all six elements from the coll collection, but the order is NOT guaranteed to be preserved. <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; set變數包含6個從coll來的元素，但不保證其排序的特性。 <br> <br>&nbsp; D. The set variable contains only three elements from the coll collection, but the order is NOT guaranteed to be preserved. <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;set變數僅包含從coll集合中的三個元素(物件)，但不保證其排序的特性。 <br> 

<div class="toccolours mw-collapsible mw-collapsed">
<span style="font-size:medium;">解答</span>

----
<div class="mw-collapsible-content">
<span style="font-size: medium;">Ans: D   </span>

<span style="font-size:medium;"> 解說:
ArrayList集合物件可以加入重複的物件(無排序性質)，此題的coll集合物件包含6個元素， 
<BR>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;但是將此coll集合物件做為HashSet集合物件的建立時，由於HashSet是不重複且不排序的性質， 
<BR>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;因此coll集合中的重覆元素不會被加到set這個集合物件中。 

<br>

</span>	
</div></div>
{{SCJP 1.6版考題講解}}