Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

[dgksharma]

Hi All,


I am new to swing when i tried to run one swing example it gives error like



Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException



Pls help on that

[Chris.Brown.SPE]

Can you post the code you are using? and even better the full stack trace to go with it?

[dgksharma]

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;


public class Example extends JFrame {

/**
*
*/
private static final long serialVersionUID = 1L;

public Example() {
initUI();
}

public final void initUI() {

JMenuBar menubar = new JMenuBar();
ImageIcon icon = new ImageIcon(getClass().getResource("exit.png"));

JMenu file = new JMenu("File");
file.setMnemonic(KeyEvent.VK_F);

JMenuItem eMenuItem = new JMenuItem("Exit", icon);
eMenuItem.setMnemonic(KeyEvent.VK_C);
eMenuItem.setToolTipText("Exit application");
eMenuItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
System.exit(0);
}

});

file.add(eMenuItem);

menubar.add(file);

setJMenuBar(menubar);

setTitle("Simple menu");
setSize(300, 200);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}

public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
Example ex = new Example();
ex.setVisible(true);
}
});
}
}




Stack Trace for exception ........

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(Unknown Source)
at Example.initUI(Example.java:29)
at Example.<init>(Example.java:23)
at Example$2.run(Example.java:59)
at java.awt.event.InvocationEvent.dispatch(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.doIntersectionPri vilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[PhHein]

ImageIcon icon = new ImageIcon(getClass().getResource("exit.png"));
Looks like exit.png isn't found.

[dgksharma]

so how can i resolve this either i should have to keep exit.png in my locale and give the exact path of exit.png

[Chris.Brown.SPE]

As long as the image is in a source folder than you should be able to reference it (aka. your code as-is works). The problem comes in when you have an image in a non source folder. That is a whole new ball game.

As a further note, i would recommend getting the resource separately from creating the ImageIcon instance. This way you can check to see if the resource exists and fail gracefully instead of having the blatant error.

[Norm]

getResource() uses the classpath to find the resource. Make sure the image file is in a folder on the classpath.