Ikk：新頁面: Given: 3. import java.util.*; 4. public class G1{ 5. public void takeList(List list){ 6. //insert code here 7. } 8. } Which three code fragments, insert...

2013-03-30T00:22:54Z

新頁面: Given: 3. import java.util.*; 4. public class G1{ 5. public void takeList(List<? extends String> list){ 6. //insert code here 7. } 8. } Which three code fragments, insert...

新頁面

Given:
3. import java.util.*;
4. public class G1{
5. public void takeList(List<? extends String> list){
6. //insert code here
7. }
8. }

Which three code fragments, inserted independently at line 6, will compile? (Choose three.)
A. list.add("foo");
B. Object o = list;
C. String s = list.get(0);
D. list = new ArrayList<String>();
E. list = new ArrayList<Object>();

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

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

<span style="font-size:medium;"> 解說:
list是指向一個放置String與其子類別型態的集合物件
B是ok的，因此任何物件皆可用Object型態的參考存取
list.get(0)傳回集合物件中第0個位置的物件，其型態是String或其子類別
list = new ArrayList<String>(); list指向內存String物件的集合物件，符合list的型態宣告。

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{{SCJP 1.6版考題講解}}

SCJP 1.6版考題 192 - 修訂歷史

Ikk：新頁面: Given: 3. import java.util.*; 4. public class G1{ 5. public void takeList(List list){ 6. //insert code here 7. } 8. } Which three code fragments, insert...