Nullpointer exception in my code..please help me.....

Well..i know java basics..but new to code something new...so please help me...im getting error

Exception in Thread "main" java.lang.nullpointerException
at lms.<init> (lms.java27)
at lms.main (lms.java76)

actually my main aim is to make a sample library management system and the member can go to management system[frame 2] only if the given username and password are same...if not a show a message[i.e,.label] will be displayed on the frame "Login Failed Please check..."..ofcourse..i still didnt write any code for frame 2 ..,but still within frame 1 only im getting this null pointer error...

please help me..and also explain me why the error occured and how u removed that..pls...

code is:-

Code:

---

//Library Management System//

import java.awt.*;
import java.awt.event.*;
class lms extends Frame implements ActionListener{
        TextField name,pswd;
        Label lbl1,lbl2,lbl3,lbl4;
        Button b1;
        lms(){
        System.out.println("Welcome to the Online Library Management System");
        lbl1=new Label("Name : ",Label.LEFT);
        lbl2=new Label("Password : ",Label.LEFT);
        lbl3=new Label("Welcome To Library Management System",Label.CENTER);

                name=new TextField(20);
                pswd=new TextField(20);
                pswd.setEchoChar('*');
                b1=new Button("OK");
                name.setBackground(Color.pink);
                name.setForeground(Color.blue);
                Font f=new Font("Arial",Font.BOLD,15);
                Font z=new Font("Arial",Font.ITALIC+Font.BOLD,15);
                name.setFont(f);
                lbl1.setFont(f);
                lbl2.setFont(f);
                lbl3.setFont(z);
                lbl4.setFont(f);
                pswd.setFont(f);
                b1.setFont(f);
               
                lbl1.setBounds(50,200,80,20);
                lbl2.setBounds(50,250,80,20);
                lbl3.setBounds(150,80,350,100);
                lbl4.setBounds(150,80,350,100);
                name.setBounds(150,200,120,25);
                pswd.setBounds(250,350,100,35);
                setLayout(null);
               
       
                b1.setFont(f);
               
                b1.setBounds(200,300,50,30);
               
       
                b1.addActionListener(this);
               
                add(lbl3);
                add(lbl1);
                add(name);
                add(lbl2);
                add(pswd);
                add(b1);
                add(lbl4);
                setSize(1000,1000);
                setTitle("LIBRARY MANAGEMENT SYSTEM");
                setVisible(true);

                addWindowListener(new WindowAdapter(){
                        public void windowClosing(WindowEvent e){
                                System.exit(0);
                        }
                });       
       
        }

        public void actionPerformed(ActionEvent ae){
                String s1=name.getText();
                        String s2=pswd.getText();               
if(ae.getSource()==b1 && s1.equals(s2)){
                        System.out.println("success");}
else{
lbl4=new Label("Login Failed Please check...",Label.LEFT);}
               
}
        public static void main(String args[]){
lms l1= new lms();
        }
}

---

Exception in Thread "main" java.lang.nullpointerException
at lms.<init> (lms.java27)

Line 27 = lbl4.setFont(f);
you realize yourself the error now?

lbl1=new Label("Name : ",Label.LEFT);
lbl2=new Label("Password : ",Label.LEFT);
lbl3=new Label("Welcome To Library Management System",Label.CENTER);
...
there is some line missing :-)

but i gave code in else block

Quote:

---

else{
lbl4=new Label("Login Failed Please check...",Label.LEFT);}

}

---

Yes but the line 34 is invoked previously - and at this time, its still null!

As eRaaa says, until that else block executes then lbl4 is null.
Hence your NullPointerException.

so what i exactly need to do now???what modification?? how can i display warning mssge in frame when else condition occur??

I'll give you a good council : learn the basics before programming gui applications! scnr!

Create a blank label at the same place as the others, then set the text when there's an error.

ok..got u,.. :D

@tolls problem solved thnx dude... :)