Ikk：新頁面: Given: 1. public class Target{ 2. private int i = 0; 3. public int addOne(){ 4. return ++i; 5. } 6. } And: 1. public class Client{ 2. public static void main(Stri...

2013-03-30T01:55:37Z

新頁面: Given: 1. public class Target{ 2. private int i = 0; 3. public int addOne(){ 4. return ++i; 5. } 6. } And: 1. public class Client{ 2. public static void main(Stri...

新頁面

Given:
1. public class Target{
2. private int i = 0;
3. public int addOne(){
4. return ++i;
5. }
6. }
And:
1. public class Client{
2. public static void main(String[] args){
3. System.out.println(new Target().addOne());
4. }
5. }

Which change can you make to Target without affecting Client?
A. Line 4 of class Target can be changed to return i++;
B. Line 2 of class Target can be changed to private int i = 1;
C. Line 3 of class Target can be changed to private int addOne(){
D. Line 2 of class Target can be changed to private Integer i = 0;

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

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

<span style="font-size:medium;"> 解說:
此題問那一個對Target進行改變而不影響Client？ (Client不用跟著改)

A 先i++再回傳值改成先回傳值再i++，二種方式的回傳值會差1，Client必須處理這個不同的值
B 將i的初值設為1，與原先的初值0不同，Client必須處理這個不同的初值
C addOne方法改成私有後，影響Client無法存取該方法
D Integer是int的包裝類別，在JDK 1.5之後，Java會對基本資料型態的int與int的包裝類別“自動地“進行基本資料的封箱(auto-boxing)
與基本資料的包裝類別拆箱動作(auto-unboxing)，所以換寫成Integer不會造成任何的影響。

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{{SCJP 1.6版考題講解}}

SCJP 1.6版考題 178 - 修訂歷史

Ikk：新頁面: Given: 1. public class Target{ 2. private int i = 0; 3. public int addOne(){ 4. return ++i; 5. } 6. } And: 1. public class Client{ 2. public static void main(Stri...