Writing to file is flawless -- reading works but returns nothing.

Question

This was a homework assignment for my 2nd Java course, and I'm not posting here for the easy way out I DO want to learn this, I'm just stuck.
Program simply -- Create/write a file with a vector inside of it, which contains an object. Allow the user to insert as many objects as they want into the vector. Once the file is created, display the contents.
Simple enough, I managed to create what I thought would work flawlessly, but when I try to read the contents of the file, the program exits code 0, without displaying the object variables I asked of it. Here is the attached code (I've left out the Person class simply to save space, but it it contained two variables (name and yob), as well as proper setters and getters):
public class homework1 {
    static Scanner keyb = new Scanner(System.in);
    public static void main(String[] args) {
        Person x = new Person();
        //I prefer flagging here
        Vector<Person> allPersons = new Vector<Person>();
        int flag = 1;
        System.out.println("Please type 'add' to add a Person to the list.");
        System.out.println("Please type 'view' to view the current list.");
        String s = keyb.next();
        if (s.equalsIgnoreCase("add")) {
            System.out.println();
            while (flag == 1) {
                System.out.print("Enter person's name: ");
                String u = keyb.next();
                x.setName(u);
                System.out.print("Enter person's year of birth: ");
                int t = keyb.nextInt();
                x.setYob(t);
                allPersons.addElement(x);
                try {
                    FileOutputStream f =
                        new FileOutputStream("C:/Documents and Settings/Constantine/Desktop/test.dat");
                    ObjectOutputStream b = new ObjectOutputStream(f);
                    b.writeObject(allPersons);
                    f.close();
                } catch (IOException e) {
                    e.toString();
                System.out.print("Add another student? (y/n): ");
                String v = keyb.next();
                if (v.equalsIgnoreCase("y")) {
                    System.out.print("Enter new student details");
                    System.out.println();
                } else {
                    System.out.println("Finished updating student list.");
                    flag--;
            if (s.equalsIgnoreCase("view")) {
                System.out.println();
                try {
                    FileInputStream f =
                        new FileInputStream("C:/Documents and Settings/Constantine/Desktop/test.dat");
                    ObjectInputStream b = new ObjectInputStream(f);
                    try{
                    allPersons = (Vector<Person>)b.readObject();
                        for(int i=0; i<allPersons.size(); i++) {
                            System.out.print(allPersons.get(i).getName());
                            System.out.print(allPersons.get(i).getYob());
                    } catch (ClassNotFoundException e) {
                        e.toString();}
                        f.close();
                        } catch (IOException e) {
                            e.toString();
        }If someone can point my in the right direction as to why my vector's object's variables aren't being displayed I'd appreciate it!
/cheers

Answer 1

OK, I added the printStackTrace() and got this returned, maybe it will mean more to you than I can understand haha
java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: Person
     at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1309)
     at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1634)
     at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
     at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1908)
     at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1832)
     at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1719)
     at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1305)
     at java.io.ObjectInputStream.readObject(ObjectInputStream.java:348)
     at homework1.main(homework1.java:107)
Caused by: java.io.NotSerializableException: Person
     at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1081)
     at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1251)
     at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1075)
     at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1375)
     at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:391)
     at java.util.Vector.writeObject(Vector.java:1018)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:585)
     at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:917)
     at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1339)
     at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1290)
     at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1079)
     at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:302)
     at homework1.main(homework1.java:68)