java INSERT query doesn't work (java.lang.NullPointerException) - java-7

Question

When I run this code I get an null pointer Exception.
try {
String sql = "INSERT INTO viwa(name,tele,surname) VALUES(?,?,?)";
pst = conn.prepareStatement(sql);
pst.setString(1, jTextField_name.getText());
pst.setString(2, jTextField_age.getText());
pst.setString(3, jTextField_tele.getText());
pst.execute();
JOptionPane.showMessageDialog(null, "Saved");
} catch (Exception e) {
e.printStackTrace();
}
*This's the full code*
` import java.sql.Connection; import java.sql.PreparedStatement;
import java.sql.ResultSet; import java.sql.Statement; import
javax.swing.JOptionPane;
public class go extends javax.swing.JFrame {
Connection conn = null;
ResultSet rs = null; PreparedStatement pst = null;
public go() {
try {
initComponents();
connect.getMyConn();
} catch (Exception e) {
e.printStackTrace();
}
}
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
jLabel3 = new javax.swing.JLabel();
jTextField_Tele = new javax.swing.JTextField();
jTextField_Surname = new javax.swing.JTextField();
jTextField_Name = new javax.swing.JTextField();
jButton_search = new javax.swing.JButton();
jButton_Update = new javax.swing.JButton();
jButton_Delete = new javax.swing.JButton();
jButton_save = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
getContentPane().setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());
jLabel1.setText("Tele");
getContentPane().add(jLabel1, new org.netbeans.lib.awtextra.AbsoluteConstraints(140, 140, -1, -1));
jLabel2.setText("Surname");
getContentPane().add(jLabel2, new org.netbeans.lib.awtextra.AbsoluteConstraints(140, 210, -1, -1));
jLabel3.setText("Name");
getContentPane().add(jLabel3, new org.netbeans.lib.awtextra.AbsoluteConstraints(140, 70, -1, -1));
jTextField_Tele.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jTextField_TeleActionPerformed(evt);
}
});
getContentPane().add(jTextField_Tele, new org.netbeans.lib.awtextra.AbsoluteConstraints(230, 140, 170, -1));
getContentPane().add(jTextField_Surname, new org.netbeans.lib.awtextra.AbsoluteConstraints(230, 210, 170, -1));
getContentPane().add(jTextField_Name, new org.netbeans.lib.awtextra.AbsoluteConstraints(230, 70, 170, -1));
jButton_search.setText("Search");
getContentPane().add(jButton_search, new org.netbeans.lib.awtextra.AbsoluteConstraints(230, 310, 120, -1));
jButton_Update.setText("Update");
getContentPane().add(jButton_Update, new org.netbeans.lib.awtextra.AbsoluteConstraints(390, 310, 120, -1));
jButton_Delete.setText("Delete");
getContentPane().add(jButton_Delete, new org.netbeans.lib.awtextra.AbsoluteConstraints(540, 310, 120, -1));
jButton_save.setText("Save");
jButton_save.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton_saveActionPerformed(evt);
}
});
getContentPane().add(jButton_save, new org.netbeans.lib.awtextra.AbsoluteConstraints(90, 310, 120, -1));
pack();
}// </editor-fold>
private void jTextField_TeleActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
}
private void jButton_saveActionPerformed(java.awt.event.ActionEvent evt) {
try {
String sql = "INSERT INTO viwa (name,tele,surname) VALUES(?,?,?)";
pst = conn.prepareStatement(sql);
pst.setString(1, jTextField_Name.getText());
pst.setString(2, jTextField_Tele.getText());
pst.setString(3, jTextField_Surname.getText());
pst.execute();
JOptionPane.showMessageDialog(this, "Saved");
} catch (Exception e) {
e.printStackTrace();
}
} `

Answer 1

Using your IDE, put a breakpoint at the start of this code and step through it watching all variables. One of your variables holds the unexpected null value. There is no other obvious reason for NPE in your code.