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

於 2013年3月16日 (六) 05:37 的修訂


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=609"