null pointer exception

[abhi_elementx]

hi. I get a NillpointerException.
Here's my code:

private void Login_ButtonMouseClicked(java.awt.event.MouseEvent evt) {                                          
String usrname = uname_TextField.getText();
        String pass = passwd_PasswordField.getText();
        String pwrd = pass.toString();
        String args[] = null;
        boolean auth_flag = false;
        
        try{
            R =  S.executeQuery("select uname, passwrd from Employee_Master;");
            
            while(R.next()){
                if(usrname.equals(R.getString("uname"))){
                    if(pwrd.equals(R.getString("passwrd"))){
           
                        this.dispose();
                     [B]args[0] = R.getString("uname")[/B]//causing nullpointerexception
                        Modules_Frame.main(args);
                        .
                        .

public class Modules_Frame extends javax.swing.JFrame {
.
.
public static void main(final String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Modules_Frame(args).setVisible(true);
            }
        });
    }

Wats the problem?
Thanks.

[BestJewSinceJC]

It might help if you pasted us the entire error message, which would probably include the line number at which this happened, and perhaps other relevant information.

[abhi_elementx]

I m trying to pass args[] to a main() function...

java.lang.NullPointerException
        at starterdialogspkg.AppStarter_Dialog.Login_ButtonMouseClicked(AppStarter_Dialog.java:148)
        at starterdialogspkg.AppStarter_Dialog.access$100(AppStarter_Dialog.java:22)
        at starterdialogspkg.AppStarter_Dialog$2.mouseClicked(AppStarter_Dialog.java:66)
        at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:253)
        at java.awt.Component.processMouseEvent(Component.java:6219)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at java.awt.Component.processEvent(Component.java:5981)
        at java.awt.Container.processEvent(Container.java:2041)
        at java.awt.Component.dispatchEventImpl(Component.java:4583)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Component.dispatchEvent(Component.java:4413)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4556)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4229)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4150)
        at java.awt.Container.dispatchEventImpl(Container.java:2085)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4413)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:178)
        at java.awt.Dialog$1.run(Dialog.java:1051)
        at java.awt.Dialog$3.run(Dialog.java:1103)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.awt.Dialog.show(Dialog.java:1101)
        at java.awt.Component.show(Component.java:1516)
        at java.awt.Component.setVisible(Component.java:1468)
        at java.awt.Window.setVisible(Window.java:841)
        at java.awt.Dialog.setVisible(Dialog.java:991)
        at starterdialogspkg.AppStarter_Dialog$3.run(AppStarter_Dialog.java:181)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

Line 148 is

args[0] = R.getString("uname");

This is declaration of args:

String[] args = null;

[BestJewSinceJC]

You declared the array incorrectly. String[] args declares an array of Strings called args that has no memory allocated to it. So basically, you named the array, but did not give it a size. You can change String[] args = null to String[] args = new String[1]; and then use args[0] = R.getString("uname"); and it should work.

[abhi_elementx]

OK. I redecalred it and it works. But the main() method does not get args...
From the main() I want to pass args to the constructor...
Plz help.

[BestJewSinceJC]

If you call the main method with Classname.main(args) it will work. Are you still getting any errors?

[abhi_elementx]

Well, I m doing the same thing.

args[0] = R.getString("uname");
 Modules_Frame.main(args);

Now this is the main():

public static void main([B]final String args[][/B]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Modules_Frame([B]args[0][/B]).setVisible(true);
        }
        }
        );
    }

This is the constructor:

public Modules_Frame(String args) {
        System.out.println("ARGS: "+args);
        MySQLConnector dbc = new MySQLConnector();
        S = dbc.connectdb();
        try{

            R = S.executeQuery("select Sales_RT, PP_RT, Reports_RT, Admin_RT from Employee_Master "+
                               "where uname = '"+args+"';");
            while(R.next()){
                if(R.getString("Sales_RT").equals("0"))Sales_Menu.setVisible(false);//setEnabled(false);
                if(R.getString("PP_RT").equals("0"))PP_Menu.setVisible(false);//setEnabled(false);
                if(R.getString("Reports_RT").equals("0"))Reports_Menu.setVisible(false);//setEnabled(false);
                if(R.getString("Admin_RT").equals("0"))Admin_Menu.setVisible(false);//setEnabled(false);
            }
        }catch(SQLException e){System.out.println(e);}
        initComponents();//This will initialize frame components...
        
    }

args can now take the correct value passed to the constructor, but the menus aren't getting disabld .
I chkd the database values. Everytime I run the program, all menus are enabled even if the user dont have the rights.
If the right i.e Sales_RT is 0, the Sales menu should be disabld and so on...
Thanks...

[BestJewSinceJC]

So you're saying that "args" is now being passed correctly, but that the database isn't working as you expected? In that case, I can't help you any further. . you have an entirely different problem now.

[abhi_elementx]

hi.
I decided to pass args directly to the constructor instead of main().
It works .
Thanks

[BestJewSinceJC]

Yeah, no problem. If you don't have any more problems you can set this to solved.