Append text inputed in the textfield into a TextArea

[romina]

I'm writing this Car Dealer program that lets a user purchase and browse through cars. while testing my program i found that when you attempt to purchase a car (which is supposed append text inputed in the textfield into a TextArea), you get a NullPointerException error
I spent maybe about 2 and a half hours trying to figure out what's wrong and still can't figure it out, can anyone give me a hand here?^^;; (the most i have found out is that the problem lies in my ActionListener...or at least i think so.)

Here's the source code:

Code:

import java.awt.*;
import java.awt.Dimension;
import java.awt.event.*;
import javax.swing.*;

public class DealerFrame extends JFrame
{
    public DealerFrame()
    {
        /*NewCars ncar1 = new NewCars("BMW", "Family Car", "New", "Z3", 35000);
        NewCars ncar2 = new NewCars("Mercedes", "SUV", "New", "LE", 35000);
        OldCars ocar1 = new OldCars("Volvo", "Family Car", "Old", "Z3", 35000);
        OldCars ocar2 = new OldCars("Toyota", "Family Car", "Old", "Camry", 20000);
        Object[] ncarArray = {ncar1, ncar2, ocar1, ocar2}; */
        Dealer carDealer = new Dealer();
        carDealer.addCar(new NewCars("BMW", "Family Car", "New", "Z3", 35000));
        carDealer.addCar(new OldCars("Toyota", "Family Car", "New", "Camry", 20000));
        
        JTextArea browsearea = new JTextArea("Welcome to __ Car Dealer we currently have: " + carDealer.getTotal() + " cars in stock.\n", 20, 10);
        getContentPane().add(browsearea, BorderLayout.CENTER);
        getContentPane().add(createDealerPanel(), BorderLayout.NORTH);
        getContentPane().add(createPurchasePanel(), BorderLayout.SOUTH);
        pack();
        show();
    }
    
    public JPanel createDealerPanel()
    {
        JLabel browselabel = new JLabel("Select a method to browse by:");
        browsecombo = new JComboBox();
        browsecombo.addItem("Car Type");
        browsecombo.addItem("Manufacturer");
        browsecombo.addItem("New Cars");
        browsecombo.addItem("Used Cars");
        
        JLabel carsets = new JLabel("Select the Type/Manufacturer you want to browse:\n");
        selectcars = new JComboBox();

        class startCheck implements ActionListener
        {  
            public void actionPerformed(ActionEvent event)
            {
                selectcars.removeAllItems();
                if((String)browsecombo.getSelectedItem() == "Car Type")
                {
                    /*selectcars.addItem("Family Cars");
                    selectcars.addItem("Minivans");
                    selectcars.addItem("Vans");
                    selectcars.addItem("SUV"); */
                    System.out.println("test");
                    //browsearea.append("test");
                }
                if((String)browsecombo.getSelectedItem() == "Manufacturer")
                {
                    System.out.println("test");
                    //browsearea.append("test");                   
                    /*selectcars.addItem("BMW");
                    selectcars.addItem("Toyota");
                    selectcars.addItem("GM");
                    selectcars.addItem("Mercedes");*/
                }
                if((String)browsecombo.getSelectedItem() == "New Cars")
                {
                    System.out.println("test");
                    //browsearea.append("test");                   
                    //browsearea.append((String)Object[0] + "\n" + (String)Object[1]);
                }
                if((String)browsecombo.getSelectedItem() == "Old Cars")
                {
                    System.out.println("test");
                    //browsearea.append("test");                    
                }
            }
        }
        startCheck listener = new startCheck();
        browsecombo.addActionListener(listener);
        
        /*class searchCar implements ActionListener
        {
            public void actionPerformed(ActionEvent event)
            {
                
                
            }
        }
        searchCar listener2 = new searchCar();
        selectcars.addActionListener(listener2);*/
        
        JPanel browsePanel1 = new JPanel();
        browsePanel1.add(browselabel);
        browsePanel1.add(browsecombo);
        browsePanel1.add(carsets);
        browsePanel1.add(selectcars);
        return browsePanel1;
    }
    
    public JPanel createPurchasePanel()
    {
        JLabel purchaseLabel = new JLabel("Purchase a Car:");
        JLabel inmanufacLabel = new JLabel("Brand:");
        final JTextField inmanufac = new JTextField(5);
        
        JLabel intypeLabel = new JLabel("Type:");
        final JTextField intype = new JTextField(5);
        
        JLabel instateLabel = new JLabel("New/Old?:");
        final JTextField instate = new JTextField(5);
        
        JLabel inpriceLabel = new JLabel("Price:");
        final JTextField inprice = new JTextField(5);
        
        JButton purchaseButton = new JButton("Purchase Car");      
        class purchaseListener implements ActionListener //problem lies somewhere here?
        {   
            public void actionPerformed(ActionEvent event)
            {
                String wstate = instate.getText();
                String wbrand = inmanufac.getText();
                String wtype = intype.getText();
                String wprice = inprice.getText();
                System.out.println("test" +  wstate + " " + wbrand + " " + wtype + " " + wprice ); //test line to check if it prints
                browsearea.append("You have purchased a " + wstate + " " + wbrand + " " + wtype + " for $" + wprice); //doesn't seem to work
            }
        }
        purchaseListener plistener = new purchaseListener();
        purchaseButton.addActionListener(plistener);
        
        JPanel browsePanel2 = new JPanel();
        browsePanel2.add(purchaseLabel);
        browsePanel2.add(inmanufacLabel);
        browsePanel2.add(inmanufac);
        browsePanel2.add(intypeLabel);
        browsePanel2.add(intype);
        browsePanel2.add(instateLabel);
        browsePanel2.add(instate);
        browsePanel2.add(inpriceLabel);
        browsePanel2.add(inprice);
        browsePanel2.add(purchaseButton);
        
        return browsePanel2;
    }
   
    private JTextArea browsearea;
    private JTextField inmanufac;
    private JTextField intype;
    private JTextField inprice;
    private JComboBox browsecombo;
    private JComboBox selectcars;

}

Thanks

[barney]

Don't have the means in which to test or modify your code with the computer I'm currently at, but I'll throw out a couple of ideas based on what I saw.

Your instance variables "browsearea" etc are declared at the bottom of your code. I'm not sure whether this makes a difference for sure, but it might be the case that you're trying to use a variable that hasn't been declared yet. However, after saying that your error doesn't seem to imply this. If this were a problem I'd expect a compilation error rather than a runtime error. So here's another thought.

You have declared "browsearea" but I don't see that you've actually instantiated it. Thus, causing a problem.

I now see that you've indeed instantiated your variable. So I guess you can safely disregard any of my thoughts. Sorry to have wasted your time. I'll take a look at it later if the question still isn't resolved.
Greetings.