2nd opinion

Question

Hi. When I get feedback from my instructor, she sometimes posts codes as examples. Sometimes I have trouble getting her codes to compile. The code below is an example of such feedback. I really wanted to see this run, but I get error messages. I asked her about it, and her reply was that it compiles and runs just fine, but I might have a copy/paste error or word wrapping error. Does anyone know where the problems are? The error messages that I receive follow the code. Thanks. You should be able to copy and paste this code and have a working program. Do you?
I posted the class with the error before and received help about fixing it, but still could not get it right. Since the teacher has now said there is nothing wrong, I posted the entire program instead of the class alone.
// save the source code in a file called, "Inventory4.java"
import java.util.Arrays;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Inventory4 {
public static void main(String[] args) {
System.out.println("\nCheckPoint: Inventory Part 4");
System.out.println("My DVD Collection\n");
Movie dvd = null;
Inventory inventory = new Inventory();
dvd = new Movie(1, "What a Girl Wants", 18, 11.99f, 2003);
System.out.println(dvd);
inventory.addMovie(dvd);
dvd = new Movie(2, "Just Married", 14, 13.85f, 2003);
System.out.println(dvd);
inventory.addMovie(dvd);
dvd = new Movie(3, "Shrek 3", 1, 19.99f, 2007);
System.out.println(dvd);
inventory.addMovie(dvd);
dvd = new Movie(4, "Superbad", 15, 19.99f, 2007);
inventory.addMovie(dvd);
System.out.println(dvd);
dvd = new Movie(5, "Holiday", 10, 21.99f, 2006);
System.out.println(dvd);
inventory.addMovie(dvd);
dvd = new Movie(6, "Monster in Law", 1, 7.99f, 2005);
System.out.println(dvd);
System.out.println("\nEnd of DVD collection!\n");
inventory.addMovie(dvd);
inventory.printInventory();
new InventoryGUI(inventory);
class DVD {
private int itemNo;
private String title;
private int inStock;
private float unitPrice;
DVD(int itemNo, String title, int inStock, float unitPrice) {
this.itemNo = itemNo;
this.title = title;
this.inStock = inStock;
this.unitPrice = unitPrice;
public int getItemNo() { return itemNo; }
public String getTitle() { return title; }
public int getInStock() { return inStock; }
public float getUnitPrice() { return unitPrice; }
public float value() {
return inStock * unitPrice;
public String toString() {
return String.format("itemNo=%2d title=%-22s inStock=%3d price=$%7.2f value=$%8.2f",
itemNo, title, inStock, unitPrice, value());
} // end DVD
class Inventory {
private final int INVENTORY_SIZE = 30;
private DVD[] items;
private int numItems;
Inventory() {
items = new Movie[INVENTORY_SIZE];
numItems = 0;
public int getNumItems() {
return numItems;
public DVD getDVD(int n) {
return items[n];
public void addMovie(DVD item) {
items[numItems] = item;
++numItems;
public double value() {
double sumOfInventory = 0.0;
for (int i = 0; i < numItems; i++)
sumOfInventory += items.value();
return sumOfInventory;
public void printInventory() {
System.out.println("\nMy DVD Inventory\n");
if (numItems <= 0) {
System.out.println("Inventory is empty.\n");
} else {
for (int i = 0; i < numItems; i++)
System.out.printf("%3d %s\n", i, items);
System.out.printf("\nTotal value in inventory is $%,.2f\n\n", value());
class Movie extends DVD {
private int movieYear;
public Movie(int MovieID, String itemName, int quantityOnHand, float itemPrice, int year) {
super(MovieID, itemName, quantityOnHand, itemPrice);
this.movieYear = movieYear;
public void setYear(int year) {
movieYear = year;
public int getMovieYear() {
return movieYear;
public float value() {
return super.value() + restockingFee();
public float restockingFee() {
return super.value() * 0.05f;
class InventoryGUI extends JFrame
private Inventory theInventory;
private int index = 0;
private final JLabel itemNumberLabel = new JLabel(" Item Number:");
private JTextField itemNumberText;
private final JLabel prodnameLabel = new JLabel(" Product Name:");
private JTextField prodnameText;
private final JLabel prodpriceLabel = new JLabel(" Price:");
private JTextField prodpriceText;
private final JLabel numinstockLabel = new JLabel(" Number in Stock:");
private JTextField numinstockText;
private final JLabel valueLabel = new JLabel(" Value:");
private JTextField valueText;
private final JLabel restockingFeeLabel = new JLabel(" Restocking Fee:");
private JTextField restockingFeeText;
private final JLabel totalValueLabel = new JLabel(" Inventory Total Value:");
private JTextField totalValueText;
private JPanel centerPanel;
private JPanel buttonPanel;
InventoryGUI(Inventory inventory) {
super("My Movie Inventory");
final Dimension dim = new Dimension(140, 20);
final FlowLayout flo = new FlowLayout(FlowLayout.LEFT);
JPanel jp;
theInventory = inventory;
centerPanel = new JPanel();
centerPanel.setLayout(new BoxLayout(centerPanel, BoxLayout.Y_AXIS));
buttonPanel = new JPanel();
JButton nextButton = new JButton("Next");
nextButton.addActionListener(new NextButtonHandler());
buttonPanel.add(nextButton);
centerPanel.add(buttonPanel);
jp = new JPanel(flo);
itemNumberLabel.setPreferredSize(dim);
jp.add(itemNumberLabel);
itemNumberText = new JTextField(3);
itemNumberText.setEditable(false);
jp.add(itemNumberText);
centerPanel.add(jp);
jp = new JPanel(flo);
prodnameLabel.setPreferredSize(dim);
jp.add(prodnameLabel);
prodnameText = new JTextField(17);
prodnameText.setEditable(false);
jp.add(prodnameText);
centerPanel.add(jp);
jp = new JPanel(flo);
prodpriceLabel.setPreferredSize(dim);
jp.add(prodpriceLabel);
prodpriceText = new JTextField(17);
prodpriceText.setEditable(false);
jp.add(prodpriceText);
centerPanel.add(jp);
jp = new JPanel(flo);
numinstockLabel.setPreferredSize(dim);
jp.add(numinstockLabel);
numinstockText = new JTextField(5);
numinstockText.setEditable(false);
jp.add(numinstockText);
centerPanel.add(jp);
jp = new JPanel(flo);
restockingFeeLabel.setPreferredSize(dim);
jp.add(restockingFeeLabel);
restockingFeeText = new JTextField(17);
restockingFeeText.setEditable(false);
jp.add(restockingFeeText);
centerPanel.add(jp);
jp = new JPanel(flo);
valueLabel.setPreferredSize(dim);
jp.add(valueLabel);
valueText = new JTextField(17);
valueText.setEditable(false);
jp.add(valueText);
centerPanel.add(jp);
jp = new JPanel(flo);
totalValueLabel.setPreferredSize(dim);
jp.add(totalValueLabel);
totalValueText = new JTextField(17);
totalValueText.setEditable(false);
jp.add(totalValueText);
centerPanel.add(jp);
setContentPane(centerPanel);
repaintGUI();
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(360, 300);
setResizable(false);
setLocationRelativeTo(null);
setVisible(true);
public void repaintGUI() {
Movie temp = (Movie) theInventory.getDVD(index);
if (temp != null) {
itemNumberText.setText("" + temp.getItemNo());
prodnameText.setText(temp.getTitle());
prodpriceText.setText(String.format("$%.2f", temp.getUnitPrice()));
restockingFeeText.setText(String.format("$%.2f", temp.restockingFee()));
numinstockText.setText("" + temp.getInStock());
valueText.setText(String.format("$%.2f", temp.value()));
totalValueText.setText(String.format("$%.2f", theInventory.value()));
class NextButtonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
int numItems = theInventory.getNumItems();
index = (++index) % numItems;
repaintGUI();
ERROR MESSAGES:
Inventory4.java:108: cannot find symbol
????symbol : method value()
????location: class DVD[]
????sumOfInventory += items.value();
???? ^
????Inventory4.java:108: inconvertible types
????found : <nulltype>
????required: double
????sumOfInventory += items.value();
???? ^
????2 errors
???? ----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.

Answer 1

he just wanted to help teach you instead of giving you the easy answer.if by "he", you mean the instructor, i would disagree. "it's correct as posted" sounds like a dismissal to me, not a teaching moment.
this is emphatically not a cut & paste error.
and personally i don't give much credit to anybody who comes here to ask about compiler problems. The compiler is very good about spelling out the file and line number at which a problem occurs. how hard can it be to open an editor or IDE, go to that line, and think hard about one line of code knowing what the complaint is about? you'll figure it out a lot faster if you just look at the code than coming here and waiting for answers passively.
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