[Java] SCJP 例題 032/例題 034 is-a/has-a

例題 032 

1. class Mammal{}
2.
3. class Raccoon extends Mammal {
4. Mammal m = new Mammal();
5. }
6.
7. class BabyRaccoon extends Mammal{}


Which four statements are true? (Choose four.)[1]

  A. Raccoon is-a Mammal.
  B. Raccoon has-a Mammal.
  C. BabyRaccoon is-a Mammal.
  D. BabyRaccoon is-a Raccoon.
  E. BabyRaccoon has-a Mammal.
  F. BabyRaccoon is-a BabyRaccoon.

[1] http://192.192.246.169/~wells/wiki/index.php/SCJP_1.6%E7%89%88%E8%80%83%E9%A1%8C_032 

這題我選 ABC (E),

看來繼承之後附類別的物件不能算式子類別的, not has-a, 

而自己也可以是自己, 雖然很怪.

之後看到在來更新一下XD

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例題 034 

 
Which four statements are true? (Choose four.)[2]
   A. Has-a relationships should never be encapsulated.
   B. Has-a relationships should be implemented using inheritance.
   C. Has-a relationships can be implemented using instance variables.
   D. Is-a relationships can be implemented using the extends keyword.
   E. Is-a relationships can be implemented using the implements keyword.
   F. The relationship between Movie and Actress is an example of an is-a relationship.
   G. An array or a collection can be used to implement a one-to-many has-a relationship. 

網站的中文說明

那四個敘述是正確的？
  A. Has-a 關係應該永遠不能被封裝
  B. Has-a 關係應該以繼承的方式實作
  C. Has-a 關係可以用物件變數的方式被實現出來
  D. Is-a關係可用extends關鍵字實現出來
  E. Is-a關係可用implements關鍵字實現出來
  F. 電影和女演員間的關係是一個Is-a關係的例子
  G. 一個陣列或一個集合可以被用來實作一對多的has-a關係 

[2] http://192.192.246.169/~wells/wiki/index.php/SCJP_1.6%E7%89%88%E8%80%83%E9%A1%8C_034

A. Has-a 可以被封裝.

B. Has-a 不可用繼承方式實做.

C. Has-a 可以用實做變數來實現.

D. Is-a  可以用繼承來實現.

E. Is-a  可以用implements實現.

F. 電影和女演員的關係是Has-a的關係.

G. 陣列和集合可被一對多的Has-a實現.