import java.awt.*;
import java.awt.event.*;
import javax.swing.border.Border;
import javax.swing.BorderFactory;
import javax.swing.*;
import java.awt.Dimension;
import javax.swing.JLabel;
import javax.swing.JComponent; 
import java.awt.Graphics;
import java.sql.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.util.Date;
public class add 
{
String msg;
JFrame f;
JPanel p;
JTextField l=new JTextField();

JLabel l1=new JLabel("REG.NO");
JTextField t=new JTextField(6);

JLabel l2=new JLabel("NAME");
JTextField t1=new JTextField(15);

JLabel l3=new JLabel("COLLEGE NAME");
JTextField t2=new JTextField(35);

JLabel l4=new JLabel("CONTACT NO");
JTextField t3=new JTextField(11);

JLabel l5=new JLabel("EMAIL-ID  ");
JTextField t4=new JTextField(20);

JLabel l6=new JLabel("PROJECT IN");
String project[]={"NETWORK","EMBEDDED","VLSI","HARDWARE","VB.NET","JAVA","ASP.NET","ECE"};

JLabel l7=new JLabel("COURSE");
String course[]={"EMBEDDED SYSTEM","VLSI DESIGN","PLC","PCB 

DESIGN","C/C++","JAVA","J2EE","VB.NET","ASP.NET","PHP","NETWORKING","WIRELESS"};

JLabel l8=new JLabel("PROJECT TITLE");
JTextArea title=new JTextArea(3,60);

JLabel l9=new JLabel("AMOUNT");
JTextField t5=new JTextField(7);
JLabel l10=new JLabel("PAID");
JTextField t6=new JTextField(7);

JLabel l11=new JLabel("BALANCE");
JTextField t7=new JTextField(7);

JLabel l12=new JLabel("ADDRESS");
JTextArea address=new JTextArea(4,40);

JButton save=new JButton("SAVE");
JButton clear=new JButton("CLEAR");
JButton print=new JButton("PRINT");


JComboBox c4=new JComboBox(project);
JComboBox c5=new JComboBox(course);

public add()
{
f=new JFrame("ADD NEW STUDENT");
p=new JPanel();
p.setLayout(new GridLayout(0, 3));
l.setText("DATE:"+""+new Date().toString());
l.setForeground(Color.RED);
Border border=BorderFactory.createLineBorder(Color.BLUE,3);
l.setBorder(border);
p.add(l);
p.add(l1);
p.add(t);

p.add(l2);
p.add(t1);
p.add(l3);
p.add(t2);
p.add(l4);
p.add(t3);
p.add(l5);
p.add(t4);
p.add(l6);
p.add(c4);
p.add(l7);

p.add(c5);
p.add(l8);
p.add(title);
p.add(l9);
p.add(t5);
p.add(l10);
p.add(t6);
p.add(l11);
p.add(t7);
p.add(l12);
p.add(address);

p.add(save);
p.add(clear);
p.add(print);

clear.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
t.setText("");
t1.setText("");
t2.setText("");
t3.setText("");
t4.setText("");
t5.setText("");
t6.setText("");
t7.setText("");
address.setText("");
title.setText("");
}
});
save.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
try
{
String date=l.getText();
double regno=Double.parseDouble(t.getText());
String name=t1.getText();
String college=t2.getText();
double contactno=Double.parseDouble(t3.getText());
String email=t4.getText();
String project=c4.getSelectedItem().toString();
String course=c5.getSelectedItem().toString();
String Title=title.getText();
double amount=Double.parseDouble(t5.getText());
double paid=Double.parseDouble(t6.getText());
double balance=Double.parseDouble(t7.getText());
String Address=address.getText();
Connection con=null;

Statement st=con.createStatement();
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:student");
int query=st.executeUpdate("INSERT INTO student" 

+"(date,regno,name,college,contactno,email,Project,course,Title,amount,paid,balance,Address)"+"VALUES(?,?,?,?,?,?

,?,?,?,?,?,?,?)");

JOptionPane.showMessageDialog(null, "Succesfully 

Saved.","Information",JOptionPane.INFORMATION_MESSAGE);
}
catch(Exception eex)
{
eex.printStackTrace();
}
}
});

f.add(p, BorderLayout.CENTER);
f.add(p);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  f.setSize(800,800);

 f.setVisible(true);

}

public static void main(String[] args)
{
add a=new add();
}
}

when i run this program... it shows the given below errors.pls clear the errors and give me correct tutorial for my knowledge improving.pls anyone help me.

E:\>java add
java.lang.NullPointerException
    at add$2.actionPerformed(add.java:143)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1
95)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.ja
a:2318)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonMode
.java:387)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:24
)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButton
istener.java:236)
    at java.awt.Component.processMouseEvent(Component.java:6263)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
    at java.awt.Component.processEvent(Component.java:6028)
    at java.awt.Container.processEvent(Container.java:2041)
    at java.awt.Component.dispatchEventImpl(Component.java:4630)
    at java.awt.Container.dispatchEventImpl(Container.java:2099)
    at java.awt.Component.dispatchEvent(Component.java:4460)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:457
)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238

    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
    at java.awt.Container.dispatchEventImpl(Container.java:2085)
    at java.awt.Window.dispatchEventImpl(Window.java:2478)
    at java.awt.Component.dispatchEvent(Component.java:4460)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThr
ad.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread
java:184)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThr
ad.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)