SCJP題庫第195題
Given:
3. import java.util.*;
4. public class Mapit{
5. public static void main(String[] args){
6. Set<Integer> set = new HashSet<Integer>();
7. Integer i1 = 45;
8. Integer i2 = 46;
9. set.add(i1);
10. set.add(i1);
11. set.add(i2); System.out.print(set.size() + " ");
12. set.remove(i1); System.out.print(set.size() + " ");
13. i2 = 47;
14. set.remove(i2); System.out.print(set.size() + " ");
15. }
16.}
What is the result?
A. 2 1 0
B. 2 1 1
C. 3 2 1
D. 3 2 2
E. Compilation fails.
F. An exception is thrown at runtime.
Ans: B
解說:
HashSet湊雜集合，用物件的特徵值計算出雜湊值，此題用Integer物件計算雜湊值，只要Integer的數字一樣計算出的雜湊值就一樣，一樣的雜湊值物件不論加(add)幾次都不會重複加入雜湊集合中。移除物件也是依據雜湊值來找出對應的物件。
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