问题

package Demo;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Map;

import javax.sound.midi.Sequence;

public class Set {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Collection c = new ArrayList();
         c.add("hello");
        // c.add(new Integer("100"));
        c.add(new Name("a", "b"));
        System.out.println(c.hashCode());
        c.add(new Name("a", "b"));
        
        // c.remove("hello");
        // c.remove(new Integer("100"));
        System.out.println(c.remove(new Name("a", "b")));
        System.out.println(c);    
        
    }
}

class Name extends Object {
    private String firstname;
    private String lastname;

    public Name(String firstname, String lastname) {
        this.firstname = firstname;
        this.lastname = lastname;
    }

    public String getFirstname() {
        return firstname;
    }

    public String getLastname() {
        return lastname;
    }

    public String toString() {
        return "the firstname is " + firstname + " the last name is " + lastname;
    }

    public boolean equals(Name a) {
        return ((this.firstname.equals(a.firstname)) && (this.lastname.equals(a.lastname)));

    }
//     public boolean equals(Object obj) {
//     if (obj instanceof Name) {
//     Name d = (Name) obj;
//     return (this.firstname.equals(d.firstname)) &&
//     (this.lastname.equals(d.lastname));
//     } else
//     return super.equals(obj);
//     }

    public int hashCode() {
        return firstname.hashCode();
    }
}