檢視 SCJP 1.6版考題 228 的原始碼

<br>&nbsp;Which three will compile and run without exception? (Choose three.) &nbsp;&nbsp; 

&nbsp; &nbsp;A. private synchronized Object o; 
<br>&nbsp; &nbsp;B. void go(){ <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; synchronized(){/* code here */} 
<br>&nbsp; C. public synchronized void go(){/* code here */} <br>&nbsp; D. private synchronized(this) void go(){/* code here */} 
<br>&nbsp; E. void go(){ <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; synchronized(Object.class){/* code here */} 
<br>&nbsp; F. void go(){ <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Object o = new Object(); <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; synchronized(o){/* code here */} 
 

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

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

<span style="font-size:medium;"> 解說:
此題問那三個將會編繹與無例外的執行？同步關鍵字synchronized可以對整個方法做同步， 
&nbsp; &nbsp; &nbsp; &nbsp; 如C，也可以對一個區塊的程式做同步， 
&nbsp; &nbsp; &nbsp; &nbsp;如E/F (要指定要取得的那個物件的lock) <br> 
<br>註：E應該是錯的，在Object類別中並沒有class這個變數，有可能這題在流傳時，出了一些問題，但，回答時還是以給的答案回。 

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{{SCJP 1.6版考題講解}}