Promblem about inheritance and saving data

Question

I have Product class (super class) and Kitchen class (sub class). When I want to create a Kitchen object and write it to a *.txt file. However the error occurs: "java.lang.NullPointerException". What is going wrong? Please help. Thanks
Product class
public Product(int aProductID, String aProductName, String aOriginalCountry,
                    double aWeight, double aPrice, String aProductCategory,
                    String aInputDate, String aExpiryDate, double aVatPrice,
                    String aManufacturerName, String aManufacturerAddress,
                    String aWarranty)
    productID = aProductID;
    productName = aProductName;
    originalCountry = aOriginalCountry;
    weight = aWeight;
    price = aPrice;
    productCategory = aProductCategory;
    inputDate = aInputDate;
    expiryDate = aExpiryDate;
    vatPrice = aVatPrice;
    manufacturerName = aManufacturerName;
    manufacturerAddress = aManufacturerAddress;
    warranty = aWarranty;
  }Kitchen class
public Kitchen(int aProductID, String aProductName, String aOriginalCountry,
                     double aWeight,
                     double aPrice, String aProductCategory,
                     String aInputDate, String aExpiryDate, double aVatPrice,
                     String aManufacturerName, String aManufacturerAddress,
                     String aWarranty)
   super(aProductID, aProductName, aOriginalCountry, aWeight, aPrice,
           aProductCategory, aInputDate, aExpiryDate, aVatPrice,
         aManufacturerName, aManufacturerAddress, aWarranty);
}The method that write the method to text file
public void writeInfo()
    try{
      PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter
      ("C:\\Documents and Settings\\Charles\\My Documents\\Kitchen.txt", true)));
      out.println();
      out.write(Integer.toString(productID));
      out.write("  ");
      out.write(productName);
      // More data to write...
      out.flush();
      out.close();
     catch(IOException ex)
        ex.printStackTrace();
}

Answer 1

This is the Product Class
package supermarket;
import java.io.*;
import javax.swing.*;
public class Product {
  // Declare variables
  protected int productID;
  protected String productName;
  protected String originalCountry;
  protected double weight;
  protected double price;
  protected String productCategory;
  protected String inputDate;
  protected String expiryDate;
  protected double vatPrice;
  protected String manufacturerName;
  protected String manufacturerAddress;
  protected String warranty;
  protected double originalPrice;
  protected double calculatedVATPrice;
  public Product() {
    productID = 0;
    productName = "";
    originalCountry = "";
    weight = 0.0;
    price = 0.0;
    vatPrice = 0.0;
    manufacturerName = "";
    manufacturerAddress = "";
    warranty = "YES";
  public Product(int aProductID, String aProductName, String aOriginalCountry,
                       double aWeight, double aPrice, String aProductCategory,
                       String aInputDate, String aExpiryDate, double aVatPrice,
                       String aManufacturerName, String aManufacturerAddress,
                       String aWarranty)
    productID = aProductID;
    productName = aProductName;
    originalCountry = aOriginalCountry;
    weight = aWeight;
    price = aPrice;
    productCategory = aProductCategory;
    inputDate = aInputDate;
    expiryDate = aExpiryDate;
    vatPrice = aVatPrice;
    manufacturerName = aManufacturerName;
    manufacturerAddress = aManufacturerAddress;
    warranty = aWarranty;
  public void writeInfo()
    try{
    PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter
    ("C:\\Documents and Settings\\Charles\\My Documents\\testing.txt", true)));
    out.println();
    out.write(Integer.toString(productID));
    out.write("  ");
    out.write(productName);
    out.write("  ");
    out.write(originalCountry);
    out.write("  ");
   // and more data to save...
    out.flush();
    out.close();
    catch(IOException ex)
     ex.printStackTrace();
public void displayInfo(JLabel D1)
    try
      BufferedReader in = new BufferedReader(new FileReader
      ("C:\\Documents and Settings\\Charles\\My Documents\\testing.txt"));
      String fromAll = in.readLine();
      D1.setText(fromAll);
    catch(IOException ex)
    ex.printStackTrace();
}This is the Kitchen class
package supermarket;
import supermarket.Product;
import java.io.*;
import javax.swing.*;
public class Kitchen extends Product{
      private int productID;
      private String productName;
      private String originalCountry;
      private double weight;
      private double price;
      private String productCategory;
      private String inputDate;
      private String expiryDate;
      private double vatPrice;
      private String manufacturerName;
      private String manufacturerAddress;
      private String warranty;
      private double originalPrice;
      private double calculatedVATPrice;
     public Kitchen() {
     super();
  // The constructor is not working......
  public Kitchen(int aProductID, String aProductName, String aOriginalCountry,
                      double aWeight, double aPrice, String aProductCategory,
                     String aInputDate, String aExpiryDate, double aVatPrice,
                     String aManufacturerName, String aManufacturerAddress, String aWarranty)
   super(aProductID, aProductName, aOriginalCountry, aWeight, aPrice,
            aProductCategory, aInputDate, aExpiryDate, aVatPrice,
            aManufacturerName, aManufacturerAddress, aWarranty);
public void writeInfo()
    try{
      PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter
     ("C:\\Documents and Settings\\Charles\\My Documents\\Kitchen.txt", true)));
      out.println();
      out.write(Integer.toString(productID));
      out.write("  ");
      out.write(productName);
      out.write("  ");
      out.write(originalCountry);
      // and more data to save...
      out.flush();
      out.close();
catch(IOException ex)
  ex.printStackTrace();
public void displayInfo(JLabel E1)
   try
     BufferedReader in = new BufferedReader(new FileReader
    ("C:\\Documents and Settings\\Charles\\My Documents\\Kitchen.txt"));
     String fromAll = in.readLine();
     E1.setText(fromAll);
   catch(IOException ex)
     ex.printStackTrace();
}Is this look better? Please help. Thanks