getting an error "Exception in thread "AWT-EventQueue-0" java.lang.NullPointerExcept"

[abhijeet shrivastava]

Hi ranchers,

I am getting an error while executing a swing application.on the click of a button,I am capturing the inputs passed by an user and passing them to my another programme,but i am getting the following error

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

code for actionperformed method is as follows.

public void actionPerformed(ActionEvent e)
{
if ("submit".equals(e.getActionCommand()))
{
variables = new HashMap(); // declared the swing class.
variables.put("ServiceURL",url.getText());
variables.put("Value",ssn.getText());
variables.put("CallingAppRole",prtcpnt_id.getText());
variables.put("Life Event Code",life_evnt_cd.getText());
variables.put("Envoirnment",envoirnment.getSelectedItem());
WSTestHarness testHarness = new WSTestHarness();
testHarness.setgui_swing(variables);
testHarness.executeTestSession();
}
}





Thanks in advance.

Regards,
Abhijeet Shrivastava

[Ilja Preuss]

Take a look at the full stack trace. It should tell you in which line the NPE occurs, which should make it rather obvious which variable is null.

[Justin Fox]

everytime i got one of those errors, it was because i was trying to
compare or modify a variable without actually declaring it first.

like for instance:

    
 
public class thisn extends JPanel
{
private JTextField theField;
 
public thisn()
{
 
if(theField.getText().equals("hello"))
{ // do something )
 
}
 
}
 

you'll get a null pointer exception, not in the event queue, because
you didnt call it in the actionlistener or mouse/key.

but it is a similar incident.

post the whole code, and I could try to help you further.

Justin

[Ilja Preuss]

Originally posted by Justin Fox:
everytime i got one of those errors, it was because i was trying to
compare or modify a variable without actually declaring it first.

Just to get the terminology straight, in your example code the theField variable *is* declared, but not *initialized*.