Why am I receiving Null pointer Exception Error.

Question

why am I receiving Null pointer Exception Error.
Hi I am developing a code for login screen. There is no syntex error as such ut I am receving the aove mentioned error. Can some one please help me ??
------------ Main.java------------------
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.sql.*;
public class Main implements ActionListener
Frame mainf;
MenuBar mb;
MenuItem List,admitform,inquiry,exit,helpn;
Menu newm,update,help;
Inquiry iq;
Admit ad;
// HosHelp hp;
Howuse hu;
Register reg;
Main()
mainf=new Frame(" Engg College V/S Mumbai University ");
     mb=new MenuBar();
     newm=new Menu(" New ");
     update=new Menu(" Update ");
     help=new Menu(" Help ");
     List=new MenuItem("List");
     admitform=new MenuItem("Admit");
     inquiry=new MenuItem("Inquiry");
     exit=new MenuItem("Exit");
     helpn=new MenuItem("How to Use?");
newm.add(List);
               newm.add(admitform);
newm.add(inquiry);
               newm.add(exit);
     help.add(helpn);
          mb.add(newm);
          mb.add(update);
          mb.add(help);
mainf.setMenuBar(mb);
               exit.addActionListener(this);
               List.addActionListener(this);
     inquiry.addActionListener(this);
     admitform.addActionListener(this);
helpn.addActionListener(this);
     mainf.setSize(400,300);
     mainf.setVisible(true);
public void actionPerformed(ActionEvent ae)
if (ae.getSource()==List)
          reg=new Register();
     if(ae.getSource()==inquiry)
     iq=new Inquiry();
if(ae.getSource()==admitform)
     ad=new Admit();
          if(ae.getSource()==helpn)
          hu=new Howuse();
          if(ae.getSource()==exit)
     mainf.setVisible(false);
public static void main(String args[])
          new Main();
-------------Register.java---------------------------
import java.awt.*;
import java.awt.event.*;
import java.sql.*;
public class Register implements ActionListener//,ItemListener
Label id,name,login,pass,repass;
Button ok,newu,cancel,check;
Button vok,iok,lok,mok,sok; //buttons for dialog boxes
TextField idf,namef,loginf,passf,repassf;
Dialog valid,invlog,less,mismat,acucreat;
Frame regis;
Checkbox admin,limit;
CheckboxGroup type;
DBconnect db;
Register()
     db=new DBconnect();
regis=new Frame("Registeration Form");
          type=new CheckboxGroup();
          admin=new Checkbox("Administrator",type,true);
          limit=new Checkbox("Limited",type,false);
          id=new Label("ID :");
name=new Label("Name :");
     login=new Label("Login :");
     pass=new Label("Password :");
     repass=new Label("Retype :");
idf =new TextField(20); idf.setEnabled(false);
     namef=new TextField(30); namef.setEnabled(false);
loginf=new TextField(30); loginf.setEnabled(false);
     passf=new TextField(30); passf.setEnabled(false);
     repassf=new TextField(30); repassf.setEnabled(false);
ok=new Button("OK"); ok.setEnabled(false);
     newu=new Button("NEW");
cancel=new Button("Cancel");
     check=new Button("Check Login"); check.setEnabled(false);
vok=new Button("OK");
     iok=new Button("OK");
          lok=new Button("OK");
          mok=new Button("OK");
          sok=new Button("OK");
valid=new Dialog(regis,"Login name is valid !");
     invlog=new Dialog(regis,"Login name already exist!");
     less=new Dialog(regis,"Password is less than six characters !");
mismat=new Dialog(regis,"password & retyped are not matching !");
acucreat=new Dialog(regis,"You have registered successfully !");
     regis.setLayout(null);
//     regis.setBackground(Color.orange);
valid.setLayout(new FlowLayout());
     invlog.setLayout(new FlowLayout());
     less.setLayout(new FlowLayout());
     mismat.setLayout(new FlowLayout());
acucreat.setLayout(new FlowLayout());
id.setBounds(35,50,80,25); //(left,top,width,hight)
idf.setBounds(125,50,40,25);
name.setBounds(35,85,70,25);
namef.setBounds(125,85,150,25);
login.setBounds(35,120,80,25);
loginf.setBounds(125,120,80,25);
check.setBounds(215,120,85,25);
     pass.setBounds(35,155,80,25);
passf.setBounds(125,155,80,25);
repass.setBounds(35,190,80,25);
repassf.setBounds(125,190,80,25);
admin.setBounds(35,225,100,25);
limit.setBounds(145,225,100,25);
          ok.setBounds(45,265,70,25);
     newu.setBounds(135,265,70,25);
cancel.setBounds(225,265,70,25);
     passf.setEchoChar('*');
repassf.setEchoChar('*');
     regis.add(id);
     regis.add(idf);
regis.add(name);
     regis.add(namef);
     regis.add(login);
     regis.add(loginf);
     regis.add(check);
regis.add(pass);
     regis.add(passf);
regis.add(repass);
     regis.add(repassf);
     regis.add(ok);
     regis.add(newu);
     regis.add(cancel);
regis.add(admin);
     regis.add(limit);
valid.add(vok);
     invlog.add(iok);     
     less.add(lok);
     mismat.add(mok);
acucreat.add(sok);
ok.addActionListener(this);
     newu.addActionListener(this);
check.addActionListener(this);
cancel.addActionListener(this);
     // limit.addItemListener(this);
     //admin.addItemListener(this);
          vok.addActionListener(this);
          iok.addActionListener(this);
     lok.addActionListener(this);
     mok.addActionListener(this);
     sok.addActionListener(this);
regis.setLocation(250,150);
regis.setSize(310,300);
regis.setVisible(true);
     public void actionPerformed(ActionEvent ae)
     if(ae.getSource()==check)
          try{
               String s2=loginf.getText();
ResultSet rs=db.s.executeQuery("select* from List");
                    while(rs.next())
               if(s2.equals(rs.getString(2).trim()))
//                    invlog.setBackground(Color.orange);
                         invlog.setLocation(250,150);
                         invlog.setSize(300,100);
               cancel.setEnabled(false);
ok.setEnabled(false);
check.setEnabled(false);
                    invlog.setVisible(true);
                         break;
                    else
                    //     valid.setBackground(Color.orange);
                         valid.setLocation(250,150);
                         valid.setSize(300,100);
               cancel.setEnabled(false);
ok.setEnabled(false);
check.setEnabled(false);
               valid.setVisible(true);
                    }catch(Exception e)
               e.printStackTrace();
if(ae.getSource()==newu)
     try{
          ResultSet rs=db.s.executeQuery("select max(ID) from List");
     while(rs.next())
String s1=rs.getString(1).trim();
               int i=Integer.parseInt(s1);
i++;
               String s2=""+i;
idf.setText(s2);
               newu.setEnabled(false);
               namef.setText(""); namef.setEnabled(true);
          loginf.setText(""); loginf.setEnabled(true);
          passf.setText(""); passf.setEnabled(true);
          repassf.setText(""); repassf.setEnabled(true);
          ok.setEnabled(true);
               check.setEnabled(true);
               }catch(Exception e)
          e.printStackTrace();
     if(ae.getSource()==ok)
          try
          String s1=idf.getText();
          String s2=loginf.getText();
          String s3=passf.getText();
     String s4=repassf.getText();
     int x=Integer.parseInt(s1);
     int t;
     if(type.getSelectedCheckbox()==admin)
          t=1;
          else
          t=0;
ResultSet rs=db.s1.executeQuery("select* from List");
               while(rs.next())
               if(s2.equals(rs.getString(2).trim()))
                    invlog.setBackground(Color.orange);
                    invlog.setLocation(250,150);
                    invlog.setSize(300,100);
               cancel.setEnabled(false);
ok.setEnabled(false);
check.setEnabled(false);
                    invlog.setVisible(true);
                    break;
               else
                    if (s3.length()<6)
                    less.setBackground(Color.orange);
                         less.setLocation(250,150);
                         less.setSize(300,100);
               ok.setEnabled(false);
                    cancel.setEnabled(false);
                    check.setEnabled(false);
                    less.setVisible(true);
else if(!(s3.equals(s4)))
                    mismat.setBackground(Color.orange);
                    mismat.setLocation(250,150);
                    mismat.setSize(300,100);
                    ok.setEnabled(false);
                    cancel.setEnabled(false);
                    check.setEnabled(false);
                    mismat.setVisible(true);
                    else
db.s1.execute("insert into User values("+x+",'"+s2+"','"+s3+"',"+t+")");
                    acucreat.setBackground(Color.orange);
                    acucreat.setLocation(250,150);
                    acucreat.setSize(300,100);
                    regis.setVisible(false);
                    acucreat.setVisible(true);
               }//else
          }//while
               } //try
          catch(Exception e1)
          // e1.printStackTrace();
          if (ae.getSource()==cancel)
          regis.setVisible(false);
          if (ae.getSource()==vok)
          ok.setEnabled(true);
               cancel.setEnabled(true);
check.setEnabled(true);
               valid.setVisible(false);
          if (ae.getSource()==iok)
          ok.setEnabled(true);
               cancel.setEnabled(true);
check.setEnabled(true);
               invlog.setVisible(false);
          if (ae.getSource()==lok)
          less.setVisible(false);
               cancel.setEnabled(true);
ok.setEnabled(true);
check.setEnabled(true);
          if (ae.getSource()==mok)
          mismat.setVisible(false);
               cancel.setEnabled(true);
ok.setEnabled(true);
check.setEnabled(true);
if (ae.getSource()==sok)
          acucreat.setVisible(false);
          ok.setEnabled(false);
               newu.setEnabled(true);
               regis.setVisible(true);
     public static void main(String args[])
     new Register();
-----------DBConnect.java------------------------------------
import java.sql.*;
public class DBconnect
Statement s,s1;
Connection c;
public DBconnect()
try
     Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
          c=DriverManager.getConnection("jdbc:odbc:Sonal");
          s=c.createStatement();
s1=c.createStatement();
     catch(Exception e)
     e.printStackTrace();
----------Login.java----------------
import java.awt.*;
import java.awt.event.*;
import java.sql.*;
public class Login implements ActionListener
Frame log;
Label login,pass;
TextField loginf,passf;
Button ok,cancel;
Dialog invalid;
Button iok;
Register reg;
DBconnect db;
Main m;
Login()
db=new DBconnect();
     log=new Frame();
     log.setLocation(250,210);
     login=new Label("Login :");
pass=new Label("Password :");
     loginf=new TextField(20);
     passf=new TextField(20);
     passf.setEchoChar('*');
     ok=new Button("OK");
     // newu=new Button("New User");
     cancel=new Button("CANCEL");
     iok=new Button(" OK ");
invalid=new Dialog(log,"Invalid User!");
//log.setBackground(Color.cyan);
//log.setForeground(Color.black);
     log.setLayout(null);
     // iok.setBackground(Color.gray);
     invalid.setLayout(new FlowLayout());
     login.setBounds(35,50,70,25); //(left,top,width,hight)
     loginf.setBounds(105,50,100,25);
     pass.setBounds(35,85,70,25);
     passf.setBounds(105,85,70,25);
     ok.setBounds(55,130,70,25);
// newu.setBounds(85,120,80,25);
cancel.setBounds(145,130,70,25);
log.add(login);
log.add(loginf);
log.add(pass);
log.add(passf);
log.add(ok);
// log.add(newu);
log.add(cancel);
     invalid.add(iok);//,BorderLayout.CENTER);
ok.addActionListener(this);
// newu.addActionListener(this);
cancel.addActionListener(this);
     iok.addActionListener(this);
log.setSize(300,170);
log.setVisible(true);
public void actionPerformed(ActionEvent a)
if(a.getSource()==ok)
     try{
          String l=loginf.getText();
          String p=passf.getText();
          ResultSet rs=db.s.executeQuery("select * from List");
          while(rs.next())
          if(l.equals(rs.getString(2).trim())&& p.equals(rs.getString(3).trim()))
                    String tp=rs.getString(4).trim();
                         int tp1=Integer.parseInt(tp);
log.setVisible(false);
if(tp1==1)
                         m=new Main();
                    // m.List.setEnabled(true);
                         else
                         m=new Main();
                         m.List.setEnabled(false);
                    break;
else
               invalid.setBackground(Color.orange);
               invalid.setSize(300,100);
               invalid.setLocation(250,210);
               cancel.setEnabled(false);
          ok.setEnabled(false);
               invalid.setVisible(true);
               }catch(Exception e1)
               e1.printStackTrace();
     if (a.getSource()==cancel)
     log.setVisible(false);
     if (a.getSource()==iok)
     invalid.setVisible(false);
     loginf.setText("");
     passf.setText("");
     cancel.setEnabled(true);
ok.setEnabled(true);
     public static void main(String[] args)
     new Login();
-------------inquiry.java---------------------------------
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.Date;
import java.text.*;
import java.sql.*;
public class Inquiry implements ActionListener
Frame inqry;
Label name,addr;
TextField namef,addrf;
Button ok,cancel,dok;
Dialog invalid;
Frame result; //Result of the inquiry....
Label lrname,lraddr,lward,lrdate,lcdate;
TextField rname,raddr,ward,rdate,cdate;
Date d;
DateFormat df;
Button rok,rcancel;
Dialog success;
Button rdok;
DBconnect db;
Inquiry()
          db=new DBconnect();
          inqry=new Frame("Inquiry Form");
          inqry.setLayout(null);
inqry.setBackground(Color.cyan);
          name=new Label(" NAME ");
          addr=new Label("ADDRESS");
          namef=new TextField(20);
          addrf=new TextField(20);
          ok=new Button("OK");
          cancel=new Button("CANCEL");
          dok=new Button("OK");
          invalid=new Dialog(inqry,"Invalid Name or Address !");
          invalid.setSize(300,100);
     invalid.setLocation(300,180);
          invalid.setBackground(Color.orange);
          invalid.setLayout(new FlowLayout());
result=new Frame(" INQUIRY RESULT "); //Result Window......
result.setLayout(null);
result.setBackground(Color.cyan);
lcdate=new Label(" DATE ");
     lrname=new Label(" NAME ");
lraddr=new Label(" ADDRESS ");
     lward=new Label(" WARD ");
     lrdate=new Label(" ADMIT-DATE ");
cdate=new TextField(10);
     rname=new TextField(20);
rname.setEnabled(false);
     raddr=new TextField(20);
     raddr.setEnabled(false);
     ward=new TextField(20);
     ward.setEnabled(false);
     rdate=new TextField(10);
     rdate.setEnabled(false);
     cdate=new TextField(20);
     d=new Date();
     df=DateFormat.getDateInstance(DateFormat.MEDIUM,Locale.KOREA);
     cdate.setText(df.format(d));
     cdate.setEnabled(false);
rok=new Button(" OK ");
     rcancel=new Button("CANCEL");
          name.setBounds(40,50,50,25);
namef.setBounds(120,50,130,25);
addr.setBounds(40,100,60,25);
addrf.setBounds(120,100,80,25);
ok.setBounds(60,145,70,25);
          cancel.setBounds(140,145,70,25);
          lcdate.setBounds(200,50,60,25); //Result Window......
cdate.setBounds(270,50,80,25);      
lrname.setBounds(35,85,70,25);
rname.setBounds(140,85,180,25);
lraddr.setBounds(35,120,80,25);
     raddr.setBounds(140,120,100,25);
lward.setBounds(35,155,80,25);
ward.setBounds(140,155,100,25);
lrdate.setBounds(30,190,80,25);
rdate.setBounds(140,190,80,25);
rok.setBounds(70,240,70,25);
rcancel.setBounds(170,240,70,25);
          inqry.add(name);
          inqry.add(namef);
          inqry.add(addr);
          inqry.add(addrf);
          inqry.add(ok);
          inqry.add(cancel);
invalid.add(dok);
     result.add(lcdate); //Result Window......
     result.add(cdate);
          result.add(lrname);
          result.add(rname);
          result.add(lraddr);
          result.add(raddr);
          result.add(lward);
          result.add(ward);
          result.add(lrdate);
          result.add(rdate);
          result.add(rok);
          result.add(rcancel);
     ok.addActionListener(this);
     cancel.addActionListener(this);
     dok.addActionListener(this);
rok.addActionListener(this); //Result Window......
     rcancel.addActionListener(this);
     inqry.setSize(280,180);
     inqry.setLocation(300,180);
     inqry.setVisible(true);
          result.setSize(400,280); //Result Window......
     result.setLocation(200,150);
     result.setVisible(false);
          public void actionPerformed(ActionEvent ae)
               if(ae.getSource()==ok)
               try
                         String nm=namef.getText();
                         String ad=addrf.getText();
                         inqry.setVisible(false);
                         ResultSet rs=db.s.executeQuery("select * from Billinformation");
                         while(rs.next())
                              String nm1=rs.getString(2).trim();
                              String ad1=rs.getString(3).trim();
                              int k=0;
                              if((nm1.equals(nm))&&(ad1.equals(ad)))
                         String adm=rs.getString(5).trim();
                         String wr=rs.getString(6).trim();
                         String bd=rs.getString(8).trim();
                              String wrb=wr+"-"+bd;
result.setVisible(true);
                              rname.setText(nm1);
                         raddr.setText(ad1);
                         ward.setText(wrb);
                         rdate.setText(adm);
k=1;
                              break;
                              }//if
                         else if(k==1)
                         invalid.setVisible(true);
                         }//while
}//try
                         catch(Exception e)
                         e.printStackTrace();
                    } //getsource ==ok
               if(ae.getSource()==cancel)
inqry.setVisible(false);
                    if(ae.getSource()==rok) //Result Window......
                    namef.setText("");
                         addrf.setText("");
                         result.setVisible(false);
                    inqry.setVisible(true);
if(ae.getSource()==rcancel)
result.setVisible(false);
                    if(ae.getSource()==dok)
                    namef.setText("");
                         addrf.setText("");
                         invalid.setVisible(false);
                         inqry.setVisible(true);
     public static void main(String args[])
          new Inquiry();
PLease Help me !!
I need this urgently.

Answer 1

can you explain what your program tries to do... and
at where it went wrong..Sir,
We are trying to make an project where we can make a person register in our data base & after which he/she can search for other user.
The logged in user can modify his/her own data but can view other ppl's data.
We are in a phase of registering the user & that's where we are stuck. The problem is that after the login screen when we hit register (OK- button) the data are not getting entered in the data base.
Can u please help me??
I am using "jdk1.3' - studnet's edition.
I am waiting for your reply.
Thanks in advance & yr interest.