SCJP題庫第201題

Given:

1. import java.util.*;

2. class A{}

3. class B extends A{}

4. public class Test{

5.   public static void main(Strang[] args){

6.     List<A> listA = new LinkedList<A>();

7.     List<B> listB = new LinkedList<B>();

8.     List<Obect> listO = new LinkedList<Obect>();

9.     //insert code here

10. }

11. public static void m1(List<? extends A> list){}

12. public static void m2(List<A> list){}

Place a result onto each method call to indicate what would happen if the method call were inserted at line 9. Note: Results can be used more than once.

Ans:

解說: 

 m1限定代入的參數是內存類別A或其子類別的串列集合 

m2限定代入內存類別A的串列集合

listA是內存類別A的集合

listB是內存類別B的集合

listO是內存類別O的集合