檢視 SCJP 1.6版考題 066 的原始碼

 5. class Thingy{ Meter m = new Meter(); }
 6. class Component {void go() { System.out.print("c");}}
 7. class Meter extends Component {void go() { System.out.print("m"); }}
 8.
 9. class DeluxeThingy extends Thingy {
 10.   public static void main(String[] args) {
 11.     DeluxeThingy dt = new DeluxeThingy();
 12.     dt.m.go();
 13.     Thingy t = new DeluxeThingy();
 14.     t.m.go();
 15.   }
 16. }
 
 
 Which two are true? (Choose two.)
   A. The output is mm.
   B. The output is mc.
   C. Component is-a Meter.
   D. Component has-a Meter.
   E. DeluxeThingy is-a Component.
   F. DeluxeThingy has-a Component.


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<span style="font-size:medium;">解答</span>

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<span style="font-size: medium;">Ans: A F    </span>

<span style="font-size:medium;"> 解說:
 Meter繼承Component
 DeluxeThingy 繼承Thingy ，Thingy 中有一個Meter物件(也是Component物件)，滿足F
 因多形原則，m物件屬於Meter，因此二個go方法皆為Meter的go，印出m
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{{SCJP 1.6版考題講解}}