SCJP 1.6版考題 122

Given:
11. public void genNumbers(){
12.   ArrayList numbers = new ArrayList();
13.   for(int i=0; i<10; i++){
14.     int value = i * ((int)Math.random());
15.     Integer intObj = new Integer(value);
16.     numbers.add(intObj);
17.   }
18.   System.out.println(numbers);
19. }


Which line of code marks the earliest point 
that an object referenced by intObj becomes a candidate for garbage collection?
 A. Line 16
 B. Line 17
 C. Line 18
 D. Line 19
 E. The object is NOT a candidate for garbage collection.

解答

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Ans: D

解說:

intObj是宣告在for迴圈裏，這個迴圈結束之後(intObj消失)，看起來15行所建的物件都要能回收，
但是這些物件被加到numbers的ArrayList(集合物件)裏，這些物件可以透過numbers被參考到，
直到numbers這個參考變數消失，也就是genNumbers方法結束。