第56題

5. class Building{}
6. public class Barn extends Building{
7. public static void main(String[] args){
8. Building build1 = new Building();
9. Barn barn1 = new Barn();
10. Barn barn2 = (Barn)build1;
11. Object obj1 = (Object)build1;
12. String str1 = (String)build1;
13. Building build2 = (Building)barn1;
14. }
15. }
Which is true?
A. if line 10 is removed, the compilation succeeds.
B. if line 11 is removed, the compilation succeeds.
C. if line 12 is removed, the compilation succeeds.
D. if line 13 is removed, the compilation succeeds.
E. More than one line must be removed for compilation to succeed.
答案：C
參考：7-8 物件的轉型
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8. Building build1 = new Building();
12. String str1 = (String)build1;
//build1 和String 沒有任何繼承關係...