SCJP題庫第026題
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.)
Ans:B C F
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)
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