"SCJP 1.6版考題 001" 修訂間的差異

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<BR>Given:
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<br>Given:  
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1. public class Threads4{  
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2. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;public static void main(String[] args){  
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<BR>1. public class Threads4{
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3. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; new Threads4.go();  
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<BR>2.   public static void main(String[] args){
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4. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }  
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<BR>3.     new Threads4.go();
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5. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;public void go(){  
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<BR>4.   }
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6. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Runnable r = new Runnable(){  
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<BR>5.   public void go(){
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7. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;public void run(){  
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<BR>6.     Runnable r = new Runnable(){
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8. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;  &nbsp;System.out.print("foo");
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<BR>7.       public void run(){
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9. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}  
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<BR>8.         System.out.print("foo");
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10. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;};  
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<BR>9.       }
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11. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Thread t = new Thread(r);  
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<BR>10.   };
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12. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; t.start();  
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<BR>11.   Thread t = new Thread(r);
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13. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; t.start();  
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<BR>12.     t.start();
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14. &nbsp; &nbsp; &nbsp; &nbsp; }  
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<BR>13.     t.start();
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15. &nbsp;}  
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<BR>14. }
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<br>  
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<BR>15.}
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What is the result?  
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<BR>
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    A. Compilation fails.  
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<BR>What is the result?
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    B. An exception is thrown at runtime.  
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<BR>A. Compilation fails.
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    C. The code executes normally and prints "foo";  
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<BR>B. An exception is thrown at runtime.
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    D. The code executes normally, but nothing is printed.
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<BR>C. The code executes normally and prints "foo";
 
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<BR>D. The code executes normally, but nothing is printed.
 
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於 2013年3月30日 (六) 09:13 的最新修訂


Given: 

1. public class Threads4{ 
2.          public static void main(String[] args){ 
3.                   new Threads4.go(); 
4.           } 
5.          public void go(){ 
6.                  Runnable r = new Runnable(){ 
7.                          public void run(){ 
8.                                   System.out.print("foo");  
9.                          } 
10.                }; 
11.               Thread t = new Thread(r); 
12.               t.start(); 
13.               t.start(); 
14.         } 
15.  } 

 
What is the result? 
   A. Compilation fails. 
   B. An exception is thrown at runtime. 
   C. The code executes normally and prints "foo"; 
   D. The code executes normally, but nothing is printed.

解答

Ans: E

解說: 一個執行緒只能啟動一次 (t.start()只能下一次)，執行緒是物件，物件相關的動作發生問題是在執行時期產生例外，而不是編譯的錯誤。

SCJP 1.6版考題講解清單
基本程式語言
物件類別與介面
繼承、覆載等
物件集合、泛型
垃圾收集
例外與斷言
多緒行緒
同步機制
其他(序別化、I/O等)
取自 "https://fgchen.com/wiki/index.php?title=SCJP_1.6版考題_001&oldid=1428"