Using Hashtable Class

Question

Hi, I try to insert two different objects into a hashtable. I want the second
one to replace the first one. I override the equals() and hashCode() methods
explicitly so that they are equal and have the same hashcodes.
But it doesn't work. Anybody can help me how I can do it ?
Thanks a lot.
Lisa
import java.util.*;
class Test {
public static void main (String[] argv){
Book b1 = new Book("aaa");
Book b2 = new Book("bbb");
Hashtable hs = new Hashtable(10);
hs.put((Book)b1, "1");
System.out.println(hs.size());
hs.put((Book)b2, "2");
System.out.println(hs.size());
public class Book {
public String name;
public Book(String name){
this.name = name;
public int hashCode(){
return 3;
public boolean equals(Book b){
return true;

Answer 1

Hello,
public boolean equals(Object b)and not
public boolean equals(Book b)One must override the function.
I hope it helps.