JFileChooser giving NullPointerException

[dragonridingsorceress]

I am trying to learn how to use the JFileChooser. I'm working in BlueJ. I keep getting a NullPointerException. Full text of the error message is at the bottom of the post.

My code is based on some of the examples I've seen online - in fact, it is almost identical. The only things I've changed (I think) are variable names. The main one I've been using for reference is from Sun's Java Tutorials.
Admittedly, I don't fully understand the whole

int returnVal = fc.showOpenDialog(parent)

thing... The way it's described (in the Sun Tutorial) seems to say that it's really only there for on-screen placement? (At least, that's how I interpretted it):

The argument to the showOpenDialog method specifies the parent component for the dialog. The parent component affects the position of the dialog and the frame that the dialog depends on. For example, the Java look and feel places the dialog directly over the parent component. If the parent component is in a frame, then the dialog is dependent on that frame. This dialog disappears when the frame is minimized and reappears when the frame is maximized.

But, here are the relevant bits of code:

public class GUI extends JFrame {
 
    //instance variables
    private JTextField filenameTF; //A textbox to display the current file
    private JButton browse; //Browse button
    JFileChooser fc;
    File gbFile; //The file I need to work with in my program
 
    public GUI() {
        // Get content pane of frame
        Container pane = getContentPane();
        //create and add GUI components to pane
 
        filenameTF = new JTextField("Select File");
        filenameTF.setEditable(false);
        pane.add(filenameTF, BorderLayout.LINE_START);
 
        browse = new JButton("Browse...");
        pane.add(browse, BorderLayout.LINE_END);
        //Define, create and register an action lister
        browse.addActionListener(new ActionListener () {
            public void actionPerformed (ActionEvent e) {
                int returnVal = fc.showOpenDialog(GUI.this);
                if (returnVal == JFileChooser.APPROVE_OPTION) {
                    gbFile = fc.getSelectedFile();
                    filenameTF.setText(gbFile.getName());
                }
            }});
    }
 
    public static void main(String[] args)
    {
        JFrame f = new GUI();
        f.pack(); //may need to change?
        f.setVisible(true);
 
        //Define, create and register a listener to quit the application
        //when the window is closed.
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }});
 
    }
}

In case I didn't mention this already, I'm just new to Java GUI programming. Pretty much everything I'm doing is drawing off examples I've been given or found online.

Here's the error: (GUI:java:43 refers to what is line 43 in my editor. I've left out a few lines that aren't relevant to the error. But it's this line:

int returnVal = fc.showOpenDialog(parent)

)

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at GUI$1.actionPerformed(GUI.java:43)
at javax.swing.AbstractButton.fireActionPerformed(Abs tractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed (AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed (DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultB uttonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseRe leased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.jav a:6041)
at javax.swing.JComponent.processMouseEvent(JComponen t.java:3265)
at java.awt.Component.processEvent(Component.java:580 6)
at java.awt.Container.processEvent(Container.java:205 8)
at java.awt.Component.dispatchEventImpl(Component.jav a:4413)
at java.awt.Container.dispatchEventImpl(Container.jav a:2116)
at java.awt.Component.dispatchEvent(Component.java:42 43)
at java.awt.LightweightDispatcher.retargetMouseEvent( Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(C ontainer.java:3986)
at java.awt.LightweightDispatcher.dispatchEvent(Conta iner.java:3916)
at java.awt.Container.dispatchEventImpl(Container.jav a:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2440 )
at java.awt.Component.dispatchEvent(Component.java:42 43)
at java.awt.EventQueue.dispatchEvent(EventQueue.java: 599)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:121)

[JosAH]

Nowhere in the source code do you actually create a JFileChooser; your member variable fc will have its initial value which is null. Read the API documentation of the JFileChooser class and see how you can create one.

kind regards,

Jos

[dragonridingsorceress]

Ah, I found the problem. I hadn't actually initialised the FileChooser.