SCJP題庫第046題

10. public class Pizza{

11.   ArrayList toppings;

12.

13.   public final void addTopping(String topping){

14.     toppings.add(topping);

15.   }

16.

17.   public void removeTopping(String topping){

18.     toppings.remove(topping);

19.   }

20. }

And:

30. class PepperoniPizza extends Pizza{

31.   public void addTopping(String topping){

32.     System.out.println("Cannot add Toppings");

33.   }

34.

35.   public void removeTopping(String topping){

36.     System.out.println("Cannot remove pepperoni");

37.   }

38. }

And:

50. Pizza pizza = new PepperoniPizza();

51. pizza.addTopping("Mushrooms");

52. pizza.removeTopping("Pepperoni");

What is the result?

A. Compilation fails.

B. Cannot add Toppings

C. The code runs with no output.

D. A NullPointerException is thrown in Line 4.

Ans:A

解說:

第13行，public final void addTopping，方法宣告成final表示子類別不能對這個方法進行覆載(overriding)