試題詳解

11. public class Key{ 

12. private long id1, 

13. private long id2；

 14. 

15. //class Key methods

 16. }

 A programmer is developing a class Key, that will be used as a key in a standard java.util.HashMap. Which two methods should be overridden to assure that Key works correctly as a key? (Choose two.)
(A) public int hashCode()
(B) public void hashCode()
(C) public int compareTo(Object o)
(D) public boolean equals(Object o)
(E)public boolean compareTo(Key k)