Which two methods should be overridden to assure that Key works correctly as a key? (Choose two.)

Given:

public class Key {
private long id1;
private long id2;

// class Key methods
}

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 boolean equals(Key k)

C.
public int compareTo(Object o)

D.
public boolean equals(Object o)

E.
public boolean compareTo(Key k)

Explanation: