Opening a file produces a java.lang.NullPointerException

Question

I have a JFrame and on the frame I have JButton, what I want is when that file is clicked that the user can load a file using the java JFileChooser.

I declare the FileChooser like this.

JFileChooser fc;

And then here is my code in the action listener for the button.

JButton btnLoad = new JButton("Load .txt");
    btnLoad.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

            int returnVal = fc.showOpenDialog(OpenFile.this);

            if (returnVal == JFileChooser.APPROVE_OPTION) {
                File file = fc.getSelectedFile();
                //This is where a real application would open the file.
                System.out.println("Opening: " + file.getName() + ".");
            } else {
                System.out.println("Open command cancelled by user.");
            }


        }
    });

The error that it is producing me is

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at maple.Netflix$2.actionPerformed(Netflix.java:73) at javax.swing.AbstractButton.fireActionPerformed(Unknown Source) at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source) at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source) at javax.swing.DefaultButtonModel.setPressed(Unknown Source) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source) at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source) at java.awt.Component.processMouseEvent(Unknown Source) at javax.swing.JComponent.processMouseEvent(Unknown Source) at java.awt.Component.processEvent(Unknown Source) at java.awt.Container.processEvent(Unknown Source) at java.awt.Component.dispatchEventImpl(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Window.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.EventQueue.dispatchEventImpl(Unknown Source) at java.awt.EventQueue.access$200(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue$4.run(Unknown Source) at java.awt.EventQueue$4.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source)

Here is line 73.

int returnVal = fc.showOpenDialog(Netflix.this);

Hovercraft Full Of Eels Hovercraft Full Of Eels · Accepted Answer · 2013-07-31T16:24:27

Just declaring the JFileChooser variable is not enough, as you need to initialize the reference variable, fc, to a valid object first before using it. This is the same as for any other reference variable.

JFileChooser fc = new JFileChooser();

Opening a file produces a java.lang.NullPointerException

2 Answers