Inheritance and Serialization

Question

Dear forum members:
I am facing some problem with one of my programs.
I have once abstract superclass name LibraryItem and 2 other sub-classes named Book and CD both of which extends LibraryItem class.
In the definition of all 3 classes I have mentioned 'implements serializable'
Now I have also designed one driver class to test objects of Book.The program is running smooth except at the last part where I am trying to write one objects of Book class in a file named "item.dat".Actually I can't write the objects in the file and I am getting the following error message -
java.io.NotSerializableException
Code for LibraryItem class
import cs1.*;
import java.io.*;
abstract public class LibraryItem implements Serializable{
protected String callNo;
protected String desc;
protected String author;
protected static int booksBorrowed = 0;
protected static int toBeShelved = 0;
protected static int onShelf = 0;
protected static int booksHold = 0;
protected boolean toShelf;
protected boolean borrowed;
protected boolean onHold;
public LibraryItem( String newCallNo, String newDesc, String newAuthor ) {
     callNo = newCallNo;
     desc = newDesc;
     author = newAuthor;
     borrowed = false;
onShelf++;
toShelf = false;     
onHold = false;
System.out.println("\n\nA new library item created!");
protected abstract String getCallNo();
protected abstract String getDesc();
protected abstract String getAuthor();
protected void setCallNo() {
     System.out.print("\nPlease enter the new call number - ");
     callNo = Keyboard.readString();
protected void setDesc() {
     System.out.print("\nPlease enter the new description for the item - ");
     desc = Keyboard.readString();
protected void setAuthor() {
     System.out.print("\nPlease enter the new author for the item - ");
     author = Keyboard.readString();
protected static int getBorrowed() {
     return booksBorrowed;
protected static int getToBeShelved() {
     return toBeShelved;
protected boolean getBorrowedStatus() {
     return borrowed;
protected static int getonShelf() {
     return onShelf;
protected static int getHold() {
return booksHold;     
protected boolean borrowed() {
boolean valid = false;
if( onHold == true ) {
if( borrowed == false && toShelf == true ) {
     borrowed = true;
     System.out.println("\nItem has been issued for the member");
booksBorrowed++;
//onShelf--;
onHold = false;
booksHold--;
valid = true;
else if( borrowed == true && toShelf == false ) {
System.out.println("\nSorry...!!!Item is already on hold!");
valid = false;
else if( borrowed == false && toShelf == false ) { 
borrowed = true;
     System.out.println("\nItem has been issued for the member");
booksBorrowed++;
onShelf--;
valid = true;
else {
System.out.println("\nSorry...!!!Item is either borrowed or not shelved!");
valid = false;
return valid;
protected boolean returned() {
boolean valid = false;
if( borrowed == true ) {
borrowed = false;
System.out.println("\nItem is returned !");
if( onHold == false )
toBeShelved++;     
toShelf = true;
booksBorrowed--;
valid = true;
     else {
     System.out.println("\nItem...!!!Book is not borrowed till now!");
valid = false;
     return valid;
protected void placeHold() {
if( borrowed == false ) {     
System.out.println("\nItem is on the shelf, it can be borrowed now!");
else if( borrowed == false && onHold == true )
System.out.println("\nItem already on hold!");
else if( borrowed == true && onHold == false ) {
onHold = true;
System.out.println("\nItem of has been placed on hold for the member!");
booksHold++;
else if( borrowed == true && onHold == true )
System.out.println("\nItem already on hold!");
protected void placeOnShelve() {
if( borrowed == false && toShelf == true && onHold == false ) {
System.out.println("\nItem of choice has been shelved and ready to be borrowed");
toBeShelved--;
toShelf = false;
onShelf++;
else      
System.out.println("\nEither the book is borrowed OR already on hold by some other member!");
public boolean equals(Object otherObject) {
          boolean result = false;          // Assume different, unless we prove otherwise!
          try {
               if (otherObject instanceof LibraryItem )
                    LibraryItem otherItem = (LibraryItem)otherObject;
                    result = (this.callNo.equals(otherItem.callNo));
          } catch (Exception e) {
               System.err.println("An error occurred during Student.equals(): " + e.getMessage());
               e.printStackTrace(System.err);
          return result;
public abstract String toString();
Code for Book class
import java.io.*;
import java.util.*;
class Book extends LibraryItem implements Serializable{
     protected String category = "";
protected BufferedReader input;     
protected int year;
     public Book(String callNo, String description, String author, int year, String category) {
          super(callNo, description, author);
          this.category = category;     
          this.year = year;
          input = new BufferedReader(new InputStreamReader(System.in));
     protected String getCallNo() {
          return callNo;
protected String getDesc() {
          return desc;
protected String getAuthor() {
          return author;
protected int getYear() {
          return year;
public String toString() {
     return(desc+" by "+author+" belongs to "+category+" category");     
protected void setCategory() throws IOException {
     String newCategory;
     System.out.println();
     System.out.print("Enter the new category for this book - ");
newCategory = input.readLine();
category = newCategory;
System.out.println("The category of the book has been set to "+category);           
Code for BookDriver class
import java.io.*;
import java.util.*;
class BookDriver {
     public static void main( String args[] ) throws IOException {
          FileOutputStream file = new FileOutputStream("LibraryAndCard.dat");
ObjectOutputStream outStream = new ObjectOutputStream(file);
          Book book = new Book("B123","C# made quiet easy","Rony", 2007, "Computer Books");
          System.out.println(book);
          book.setCategory();
     outStream.writeObject(book);      
     outStream.close();
Pls do help me with your suggestions.when it is trying to write the object in the specified file in the statement outStream.writeObject(book), its throwing the above mentioned exception!
thanx and regards
RK

Answer 1

What is the full error that is displayed in the console? It seems to me (although Im not too familiar with serialization) that its probably one of the class variables in Book that is not serializable (The BufferedReader doesn't seem to implement seriablizable???)
If it is just this then you can presumably just write a new writeObject(inputstream) method to replace the defaultWriteObject in the inputstream? Just make it write the vital data about the reader instead of writing the object. Or you could write a little class extending bufferedreader and just adding serialization.
You would need to do an equivalent readObject too.
Hope that is of some help