Help Needed: Serialization Problem

Question

I've got a problem with serialization, which is better illustrated with an example (slightly modified version of example in Tech Tips, February 29, 2000, Serialization in the Real World. The problem is that comparing serialized static final fields doesn't return correct result. Any help on how to fix this problem would be greatly appreciated. Thanks in advance. Here is the code:
====================
import java.io.*;
class Gender implements Serializable {
String val;
private Gender(String v) {
val = v;
public static final Gender male = new Gender("male");
public static final Gender female = new Gender("female");
public String toString() {
return val;
public class Person implements Serializable {
public String firstName;
public String lastName;
private String password;
transient Thread worker;
public Gender gender;
public Person(String firstName,
String lastName,
String password,
Gender gender) {
this.firstName = firstName;
this.lastName = lastName;
this.password = password;
this.gender = gender;
public boolean isMale() {
return gender == Gender.male;
public boolean isFemale() {
return gender == Gender.female;
public String toString() {
return new String(firstName + " " + lastName);
public static void main(String [] args) {
Person p = new Person("Fred", "Wesley", "cantguessthis", Gender.male);
//-NOTE: there ia no problem with this check
if (p.isMale()) {
System.out.println("a male: " + p);
} else if (p.isFemale()) {
System.out.println("a female: " + p);
} else System.out.println("strange");
class WritePerson {
public static void main(String [] args) {
Person p = new Person("Fred", "Wesley", "cantguessthis", Gender.male);
ObjectOutputStream oos = null;
try {
oos = new ObjectOutputStream(
new FileOutputStream(
"Person.ser"));
oos.writeObject(p);
catch (Exception e) {
e.printStackTrace();
finally {
if (oos != null) {
try {oos.flush();}
catch (IOException ioe) {}
try {oos.close();}
catch (IOException ioe) {}
class ReadPerson {
public static void main(String [] args) {
ObjectInputStream ois = null;
try {
ois = new ObjectInputStream(
new FileInputStream(
"Person.ser"));
Person p = (Person)ois.readObject();
//-NOTE: this is the problem: the check returns false
if (p.isMale()) {
System.out.println("a male: " + p);
} else if (p.isFemale()) {
System.out.println("a female " + p);
} else System.out.println("strange");
catch (Exception e) {
e.printStackTrace();
finally {
if (ois != null) {
try {ois.close();}
catch (IOException ioe) {}
}

Answer 1

The Gender class implements a type-safe enumeration, but its implementation needs to be improved to ensure that re-creating a Gender object via deserialization doesn't create new objects but uses the existing objects. See this article for details on how that's done:
http://developer.java.sun.com/developer/Books/shiftintojava/page1.html