SCJP 1.6版考題 026

10. interface Jumper{public void jump();}
...
20. class Animal{}
...
30. class Dog extends Animal{
31.   Tail tail;
32. }
...
40. class Beagle extends Dog implements Jumper{
41.   public void jump(){}
42. }
...
50. class Cat implements Jumper{
51.   public void jump(){}
52. }


Which three are true? (Choose three.) 

   A. Cat is-a Animal
   B. Cat is-a Jumper
   C. Dog is-a Animal
   D. Dog is-a Jumper
   E. Cat has-a Animal
   F. Beagle has-a Tail
   G. Beagle has-a Jumper

解答

---

Ans: B C F

解說:

extends擴充，即是繼承後擴充的意思 (C)
implements是實作介面，也是另一種繼承，只是將介面中所制定的各種規格一一實作出來，具備介面制定的能力！(B)
Beagle 繼承Dog，而Dog類別has-a Tail，因此Beagle 也有Tail (F)