檢視 SCJP 1.6版考題 099 的原始碼

 3. interface Animal{void makeNoise();}
 4. class Horse implements Animal{
 5.   Long weight = 1200L;
 6.   public void makeNoise(){System.out.println("whinny");}
 7. }
 8. public class lcelandic extends Horse{
 9.   public void makeNoise(){System.out.println("vinny");}
 10. public static void main(String[] args) {
 11.   Icelandic i1 = new lcelandic();
 12.   Icelandic i2 = new lcelandic();
 13.   Icelandic i3 = new lcelandic();
 14.   i3 = i1; i1 = i2; i2 = null; i3 = i1;
 15. }
 16.}
 
 
 When line 14 is reached, how many objects are eligible for the garbage collector?
   A. 0
   B. 1
   C. 2
   D. 3
   E. 4
   F. 6

<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: C   </span>

<span style="font-size:medium;"> 解說:
 i3=i1，i3原本指向的物件可回收，i1=i2， 
 i1原本指向的物件因被i3參考不能被回收，i2=null，
 i2指向的物件被i1參考不能回收，i3=i1，i3指向的物件可回收
 可以畫圖來看比較清楚。

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