Ikk：新頁面: Given: 1. public class GC{ 2. private Object o; 3. private void doSomethingElse(Object obj){o = obj;} 4. public void doSomething(){ 5. Object o = new Object(); 6. ...

2013-03-30T04:09:18Z

新頁面: Given: 1. public class GC{ 2. private Object o; 3. private void doSomethingElse(Object obj){o = obj;} 4. public void doSomething(){ 5. Object o = new Object(); 6. ...

新頁面

Given:
1. public class GC{
2. private Object o;
3. private void doSomethingElse(Object obj){o = obj;}
4. public void doSomething(){
5. Object o = new Object();
6. doSomethingElse(o);
7. o = new Object();
8. doSomethingElse(null);
9. o = null;
10. }
11.}
When the doSomething method is called,
after which line does the Object created in line 5 become available for garbage collection?
A. Line 5
B. Line 6
C. Line 7
D. Line 8
E. Line 9
F. Line 10

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

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

<span style="font-size:medium;"> 解說:
方法變數o指向第5建立的物件在第6行方法doSomethingElse執行時，被GC物件的o參考，
即使第8行方法變數o指向新的物件也還是被參考住而不是垃圾物件的候選，
直到再次呼叫doSomethingElse方法，將GC物件的o設為null，第5行建立的物件就沒有指向。

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{{SCJP 1.6版考題講解}}

SCJP 1.6版考題 120 - 修訂歷史

Ikk：新頁面: Given: 1. public class GC{ 2. private Object o; 3. private void doSomethingElse(Object obj){o = obj;} 4. public void doSomething(){ 5. Object o = new Object(); 6. ...