SCJP 1.6版考題 109

Given:
5. class Payload{
6.     private int weight;
7.     public Payload (int w){weight = w;}
8.     public void setWeight(int w){weight = w;}
9.     public String toString(){return Integer.toString(weight);}
10. }
11. public class TestPayload{
12. static void changePayload(Payload p){/* insert code */}
13. public static void main(String[] args){
14.   Payload p = new Payload(200);
15.   p.setWeight(1024);
16.   changePayload(p);
17.   System.out.println("p is " + p);
18. }}


Which code fragment, inserted at the end of line 12, produces the output p is 420?
  A. p.setWeight(420);
  B. p.changePayload(420);
  C. p = new Payload(420);
  D. Payload.setWeight(420);
  E. p = Payload.setWeight(420);

解答

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Ans: A

解說:

 此題P物件以字串的表現請看第15行的toString方法，此方法輸出物件中的屬性weight，
 因此，為了要使P輸出420，第20行中必須用setWeight方法設定weight值為420