第38題

1. class One{
2. public One foo(){return this;}
3. }
4. class Two extends One{
5. public One foo(){return this;}
6. }
7. class Three extends Two{
8. //insert method here
9. }
Which two methods, inserted individually, correctly complete the Three class? (Choose two.)
A. public void foo(){}
B. public int foo(){return 3;}
C. public Two foo(){return this;}
D. public One foo(){return this;}
E. public Object foo(){return this;}

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答案：CD
參考：6-5 繼承
繼承及改寫的觀念
A. public void foo(){} //試圖改寫第5行但回傳是錯的
B. public int foo(){return 3;} //試圖改寫第5行但回傳是錯的
C. public Two foo(){return this;}
D. public One foo(){return this;}
E. public Object foo(){return this;} //試圖改寫第5行但回傳是錯的