Please Help - Need Help with Buttons for GUI for assignment. URGENT!!

Question

Can someone please help me with the buttons on this program? I cannot figure out how to get them to work.
Thanks!!!
import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat;
import javax.swing.*;
import javax.swing.JButton;
public class InventoryTAH implements ActionListener
    Maker[] proMaker;
    JTextField[] fields;
    NumberFormat nf;
    public void actionPerformed(ActionEvent e)
        int index = ((JComboBox)e.getSource()).getSelectedIndex();
        populateFields(index);
    public static void main(String[] args)
        try
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        catch (Exception e)
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        InventoryTAH test = new InventoryTAH();
        test.initMakers();
        test.showGUI();
        test.populateFields(0);
    private void initMakers() {
        proMaker = new Maker[10];
        proMaker[0] = new Maker( 1, "Pens",1.59,100,"Bic");
        proMaker[1] = new Maker( 2, "Pencils", .65, 100,"Mead");
        proMaker[2] = new Maker( 3, "Markers", 1.29, 100,"Sharpie");
        proMaker[3] = new Maker( 4, "Paperclips", 1.19, 100,"Staples");
        proMaker[4] = new Maker( 5, "Glue", .85, 100,"Elmer's");
        proMaker[5] = new Maker( 6, "Tape", .50, 100,"3m");
        proMaker[6] = new Maker( 7, "Paper", 1.85, 100,"Mead");
        proMaker[7] = new Maker( 8, "Stapler", 2.21, 100,"Swingline");
        proMaker[8] = new Maker( 9, "Folders", .50, 100,"Mead");
        proMaker[9] = new Maker( 10, "Rulers", .27, 100,"Stanley");      
      int maxNum = 10;
      int currentNum = 0;
      int currentInv = 0;
         Action firstAction = new AbstractAction("First")
          public void actionPerformed(ActionEvent evt)
               currentInv = 0;
               int populateFields;
      JButton firstButton = new JButton(firstAction);
      Action previousAction = new AbstractAction("Previous")
          public void actionPerformed(ActionEvent evt)
               currentInv--;
               if (currentInv < 0)
                    currentInv = maxNum - 1;
               int populateFields;
      JButton previousButton = new JButton(previousAction);
      Action nextAction  = new AbstractAction("Next")
          public void actionPerformed(ActionEvent evt)
               currentInv++;
               if (currentInv >= currentNum)
                    currentInv = 0;
              int populateFields;
      JButton nextButton = new JButton(nextAction);
      Action lastAction = new AbstractAction("Last")
          public void actionPerformed(ActionEvent evt)
               currentInv = currentNum - 1;
               int populateFields;
      JButton lastButton = new JButton(lastAction);
          JPanel buttonPanel = new JPanel( );
    private void showGUI() {
        JLabel l;
        JButton button1;
            JButton button2;
        fields = new JTextField[8];
        JFrame f = new JFrame("Inventory");
        Container cp = f.getContentPane();
        cp.setLayout(new GridBagLayout());
        cp.setBackground(UIManager.getColor(Color.BLACK));
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = 1;
        c.gridheight = 1;
        c.insets = new Insets(2, 2, 2, 2);
        c.anchor = GridBagConstraints.EAST;
        cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('a');
        cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('b');
        cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('c');
        cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('d');
        cp.add(l = new JLabel("Total cost of Item: $", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('e');
        cp.add(l = new JLabel("Total Value of Merchandise in Inventory: $", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('f');
        cp.add(l = new JLabel("Manufacturer:", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('g');
        cp.add(l = new JLabel("Restocking Fee: $", SwingConstants.CENTER), c);
        l.setDisplayedMnemonic('h');
            c.gridx = 1;
        c.gridy = 0;
        c.weightx = 1.0;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.anchor = GridBagConstraints.CENTER;
        cp.add(fields[0] = new JTextField(), c);
        fields[0].setFocusAccelerator('a');
        c.gridx = 1;
        c.gridy = GridBagConstraints.RELATIVE;
        cp.add(fields[1] = new JTextField(), c);
        fields[1].setFocusAccelerator('b');
        cp.add(fields[2] = new JTextField(), c);
        fields[2].setFocusAccelerator('c');
        cp.add(fields[3] = new JTextField(), c);
        fields[3].setFocusAccelerator('d');
        cp.add(fields[4] = new JTextField(), c);
        fields[4].setFocusAccelerator('e');
        cp.add(fields[5] = new JTextField(), c);
        fields[5].setFocusAccelerator('f');
        cp.add(fields[6] = new JTextField(), c);
        fields[6].setFocusAccelerator('g');
        cp.add(fields[7] = new JTextField(), c);
        fields[7].setFocusAccelerator('h');
        c.weightx = 0.0;
        c.fill = GridBagConstraints.NONE;
          cp.add(firstButton);
          cp.add(previousButton);
          cp.add(nextButton);
          cp.add(lastButton);
                      JComboBox combo = new JComboBox();
        for(int j = 0; j < proMaker.length; j++)
            combo.addItem(proMaker[j].getName());
        combo.addActionListener(this);
            cp.add(combo);
            cp.add(button1 = new JButton("   "), c);
        f.pack();
        f.addWindowListener(new WindowAdapter()
            public void windowClosing(WindowEvent evt)
                System.exit(0);
        f.setVisible(true);
  private void populateFields(int index) {
        Maker maker = proMaker[index];
        fields[0].setText(Long.toString(maker.getNumberCode()));
        fields[1].setText(maker.getName());
        fields[2].setText(Long.toString(maker.getUnits()));
        fields[3].setText(Double.toString(maker.getPrice()));
        fields[4].setText(Double.toString(maker.getSum()));
        fields[5].setText(Double.toString(maker.totalAllInventory(proMaker)));
        fields[6].setText(maker.getManufact());
        fields[7].setText(Double.toString(maker.getSum()*.05));       
class Maker {
    int itemNumber;
    String name;
    int units;
    double price;
    String manufacturer;
    public Maker(int n, String name, double price, int units, String manufac) {
        itemNumber = n;
        this.name = name;
        this.price = price;
        this.units = units;
        manufacturer = manufac;
    public int getNumberCode() { return itemNumber; }
    public String getName() { return name; }
    public int getUnits() { return units; }
    public double getPrice() { return price; }
    public double getSum() { return units*price; }
    public String getManufact() { return manufacturer; }
    public double totalAllInventory(Maker[] makers) {
        double total = 0;
        for(int j = 0; j < makers.length; j++)
            total += makers[j].getSum();
        return total;
}}

Answer 1

// I have made some modifications. Please try this.
import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat;
import javax.swing.*;
import javax.swing.JButton;
public class InventoryTAH implements ActionListener
Maker[] proMaker;
JTextField[] fields;
NumberFormat nf;
int currentInv = 0;
public void actionPerformed(ActionEvent e)
currentInv= ((JComboBox)e.getSource()).getSelectedIndex();
populateFields(currentInv);
public static void main(String[] args)
try
UIManager.setLookAndFeel(
"com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
catch (Exception e)
System.err.println(e.getClass().getName() + ": " + e.getMessage());
InventoryTAH test = new InventoryTAH();
test.initMakers();
test.showGUI();
test.populateFields(0);
private void initMakers() {
proMaker = new Maker[10];
proMaker[0] = new Maker( 1, "Pens",1.59,100,"Bic");
proMaker[1] = new Maker( 2, "Pencils", .65, 100,"Mead");
proMaker[2] = new Maker( 3, "Markers", 1.29, 100,"Sharpie");
proMaker[3] = new Maker( 4, "Paperclips", 1.19, 100,"Staples");
proMaker[4] = new Maker( 5, "Glue", .85, 100,"Elmer's");
proMaker[5] = new Maker( 6, "Tape", .50, 100,"3m");
proMaker[6] = new Maker( 7, "Paper", 1.85, 100,"Mead");
proMaker[7] = new Maker( 8, "Stapler", 2.21, 100,"Swingline");
proMaker[8] = new Maker( 9, "Folders", .50, 100,"Mead");
proMaker[9] = new Maker( 10, "Rulers", .27, 100,"Stanley");
     int maxNum = 10;
     int currentNum = 0;
Action firstAction = new AbstractAction("First")
          public void actionPerformed(ActionEvent evt)
               currentInv = 0;
               populateFields(currentInv);
     JButton firstButton = new JButton(firstAction);
     Action previousAction = new AbstractAction("Previous")
          public void actionPerformed(ActionEvent evt)
               currentInv--;
               if (currentInv < 0)
                    currentInv = maxNum - 1;
               populateFields(currentInv);
     JButton previousButton = new JButton(previousAction);
     Action nextAction = new AbstractAction("Next")
          public void actionPerformed(ActionEvent evt)
               currentInv++;
               if (currentInv >= maxNum)
                    currentInv = 0;
          populateFields(currentInv);
     JButton nextButton = new JButton(nextAction);
     Action lastAction = new AbstractAction("Last")
          public void actionPerformed(ActionEvent evt)
               currentInv = maxNum-1;
               populateFields(currentInv);
     JButton lastButton = new JButton(lastAction);
          JPanel buttonPanel = new JPanel( );
private void showGUI() {
JLabel l;
JButton button1;
          JButton button2;
fields = new JTextField[8];
JFrame f = new JFrame("Inventory");
Container cp = f.getContentPane();
cp.setLayout(new GridBagLayout());
cp.setBackground(UIManager.getColor(Color.BLACK));
GridBagConstraints c = new GridBagConstraints();
c.gridx = 0;
c.gridy = GridBagConstraints.RELATIVE;
c.gridwidth = 1;
c.gridheight = 1;
c.insets = new Insets(2, 2, 2, 2);
c.anchor = GridBagConstraints.EAST;
cp.add(l = new JLabel("Item Number:", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('a');
cp.add(l = new JLabel("Item Name:", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('b');
cp.add(l = new JLabel("Number of Units in Stock:", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('c');
cp.add(l = new JLabel("Price per Unit: $", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('d');
cp.add(l = new JLabel("Total cost of Item: $", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('e');
cp.add(l = new JLabel("Total Value of Merchandise in Inventory: $", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('f');
cp.add(l = new JLabel("Manufacturer:", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('g');
cp.add(l = new JLabel("Restocking Fee: $", SwingConstants.CENTER), c);
l.setDisplayedMnemonic('h');
          c.gridx = 1;
c.gridy = 0;
c.weightx = 1.0;
c.fill = GridBagConstraints.HORIZONTAL;
c.anchor = GridBagConstraints.CENTER;
cp.add(fields[0] = new JTextField(), c);
fields[0].setFocusAccelerator('a');
c.gridx = 1;
c.gridy = GridBagConstraints.RELATIVE;
cp.add(fields[1] = new JTextField(), c);
fields[1].setFocusAccelerator('b');
cp.add(fields[2] = new JTextField(), c);
fields[2].setFocusAccelerator('c');
cp.add(fields[3] = new JTextField(), c);
fields[3].setFocusAccelerator('d');
cp.add(fields[4] = new JTextField(), c);
fields[4].setFocusAccelerator('e');
cp.add(fields[5] = new JTextField(), c);
fields[5].setFocusAccelerator('f');
cp.add(fields[6] = new JTextField(), c);
fields[6].setFocusAccelerator('g');
cp.add(fields[7] = new JTextField(), c);
fields[7].setFocusAccelerator('h');
c.weightx = 0.0;
c.fill = GridBagConstraints.NONE;
          cp.add(firstButton);
          cp.add(previousButton);
          cp.add(nextButton);
          cp.add(lastButton);
                    JComboBox combo = new JComboBox();
for(int j = 0; j < proMaker.length; j++)
combo.addItem(proMaker[j].getName());
combo.addActionListener(this);
          cp.add(combo);
          cp.add(button1 = new JButton(" "), c);
f.pack();
f.addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent evt)
System.exit(0);
f.setVisible(true);
private void populateFields(int index) {
Maker maker = proMaker[index];
fields[0].setText(Long.toString(maker.getNumberCode()));
fields[1].setText(maker.getName());
fields[2].setText(Long.toString(maker.getUnits()));
fields[3].setText(Double.toString(maker.getPrice()));
fields[4].setText(Double.toString(maker.getSum()));
fields[5].setText(Double.toString(maker.totalAllInventory(proMaker)));
fields[6].setText(maker.getManufact());
fields[7].setText(Double.toString(maker.getSum()*.05));
class Maker {
int itemNumber;
String name;
int units;
double price;
String manufacturer;
public Maker(int n, String name, double price, int units, String manufac) {
itemNumber = n;
this.name = name;
this.price = price;
this.units = units;
manufacturer = manufac;
public int getNumberCode() { return itemNumber; }
public String getName() { return name; }
public int getUnits() { return units; }
public double getPrice() { return price; }
public double getSum() { return units*price; }
public String getManufact() { return manufacturer; }
public double totalAllInventory(Maker[] makers) {
double total = 0;
for(int j = 0; j < makers.length; j++)
total += makers[j].getSum();
return total;
}}