Problem with one of my buttons in java swing

Question

Gary,
I am trying to create a button that will link to my .txt file located on my desktop then when I go to display button and press it there are errors coming up that I dont get. The display button should display the results of the previous search inside in a textArea I was wondering if you could help me
Rgds
Tony
Here is the code
//creates a button that can be used to display the results in the text area
display_button = new JButton("Display results on text area");
display_button.addActionListener(new ActionListener()
public void actionPerformed(ActionEvent event_performed)
try
URL url = null;
String line;
InputStream in = url.openStream();
BufferedReader dis = new BufferedReader(new InputStreamReader(in));
buffer = new StringBuffer();
while((line = dis.readLine()) != null)
buffer.append(line + "\n");
in.close();
catch(IOException file_error)
textArea.append("IO Exception = " + file_error);
// Load the file into the TextArea.
textArea.append(buffer.toString());
} //End of display button actionPerformed
}); //End of display_button actionListener
The resulting errors are:
     at tony_buckley_project.Applet2.readFile(Applet2.java:330)
     at tony_buckley_project.Applet2.start(Applet2.java:356)
     at tony_buckley_project.Applet2$3.actionPerformed(Applet2.java:250)
     at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1764)
     at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1817)
     at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:419)
     at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:257)
     at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:245)
     at java.awt.Component.processMouseEvent(Component.java:5134)
     at java.awt.Component.processEvent(Component.java:4931)
     at java.awt.Container.processEvent(Container.java:1566)
     at java.awt.Component.dispatchEventImpl(Component.java:3639)
     at java.awt.Container.dispatchEventImpl(Container.java:1623)
     at java.awt.Component.dispatchEvent(Component.java:3480)
     at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3450)
     at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3165)
     at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3095)
     at java.awt.Container.dispatchEventImpl(Container.java:1609)
     at java.awt.Window.dispatchEventImpl(Window.java:1590)
     at java.awt.Component.dispatchEvent(Component.java:3480)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:450)
     at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
     at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

Answer 1

One problem that i can see from your code is that you are writing
url = null;
and then
InputStream in = url.openStream();
should give u an exception right there...