I get the message Exception in thread "main" java.lang.StackOverflowError

Question

I'm trying to make a program for my class and when I run the program I get the error Exception in thread "main" java.lang.StackOverflowError, I have looked up what it means and I don't see where in my program would be giving the error, can someone please help me, here is the program
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
// This visual application allows users to "shop" for items,
// maintaining a "shopping cart" of items purchased so far.
public class ShoppingApp extends JFrame
implements ActionListener {
private JButton addButton, // Add item to cart
removeButton; // Remove item from cart
private JTextArea itemsArea, // Where list of items for sale displayed
cartArea; // Where shopping cart displayed
private JTextField itemField, // Where name of item entered
messageField; // Status messages displayed
private ShoppingCart cart; // Reference to support object representing
// Shopping cart (that is, the business logic)
String itemEntered;
public ShoppingApp() {
// This array of items is used to set up the cart
String[] items = new String[5];
items[0] = "Computer";
items[1] = "Monitor";
items[2] = "Printer";
items[3] = "Scanner";
items[4] = "Camera";
// Construct the shopping cart support object
cart = new ShoppingCart(items);
// Contruct visual components
addButton = new JButton("ADD");
removeButton = new JButton("REMOVE");
itemsArea = new JTextArea(6, 8);
cartArea = new JTextArea(6, 20);
itemField = new JTextField(12);
messageField = new JTextField(20);
// Listen for events on buttons
addButton.addActionListener(this);
removeButton.addActionListener(this);
// The list of items is not editable, and is in light grey (to
// make it distinct from the cart area -- this would be done
// better by using the BorderFactory class).
itemsArea.setEditable(false);
itemsArea.setBackground(Color.lightGray);
cartArea.setEditable(false);
// Write the list of items into the itemsArea
itemsArea.setText("Items for sale:");
for (int i = 0; i < items.length; i++)
itemsArea.append("\n" + items);
// Write the initial state of the cart into the cartArea
cartArea.setText("No items in cart");
// Construct layouts and add components
JPanel mainPanel = new JPanel(new BorderLayout());
getContentPane().add(mainPanel);
JPanel controlPanel = new JPanel(new GridLayout(1, 4));
controlPanel.add(new JLabel("Item: ", JLabel.RIGHT));
controlPanel.add(itemField);
controlPanel.add(addButton);
controlPanel.add(removeButton);
mainPanel.add(controlPanel, "North");
mainPanel.add(itemsArea, "West");
mainPanel.add(cartArea, "Center");
mainPanel.add(messageField, "South");
public void actionPerformed(ActionEvent e)
itemEntered=itemField.getText();
if (addButton==e.getSource())
cart.addComputer();
     messageField.setText("Computer added to the shopping cart");
public static void main(String[] args) {
ShoppingApp s = new ShoppingApp();
s.setSize(360, 180);
s.show();
this is a seperate file called ShoppingCart
public class ShoppingCart extends ShoppingApp
private String[] items;
private int[] quantity;
public ShoppingCart (String[] inputitems)
super();
items=inputitems;
quantity=new int[items.length];
public void addComputer()
int x;
for (x=0; "computer".equals(itemEntered); x++)
     items[x]="computer";
please somebody help me, this thing is due tomorrow I need help asap!

Answer 1

First, whenever you post, there is a link for Formatting Help. This link takes you to here: http://forum.java.sun.com/features.jsp#Formatting and tells you how to use the code and /code tags so any code you post will be easily readable.
Your problem is this: ShoppingApp has a ShoppingCart and ShoppingCart is a ShoppingApp - that is ShoppingCart extends ShoppintApp. You are saying that ShoppingCart is a ShoppingApp - which probably doesn't make sense. But the problem is a child class always calls one of its parent's constructors. So when you create a ShoppingApp, the ShoppingApp constructor tries to create a ShoppingCart. The ShoppingCart calls its superclass constructor, which tries to create a ShoppingCart, which calls its superclass constructor, which tries to create a ShoppingCart, which...
It seems like ShoppingCart should not extend ShoppingApp.