JDBC Netbeans java+mysql 项目连接语句显示错误

Question

我尝试使用java语言将数据插入MySQL数据库，我使用Netbeans作为开发IDE。但我的代码中有一些错误。我还在项目库中添加了 JDBC 驱动程序，但getConnection在代码中显示错误。

线程“AWT-EventQueue-0”中的异常 java.lang.RuntimeException：无法编译的源代码 - 错误的符号类型：java.lang.Object.getConnection

你能帮我解决代码中的这些错误吗？

Answer 1

您只需删除该行：private Object DriverManager;package project1;import java.awt.HeadlessException;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import javax.swing.*;&nbsp;public class NewJFrame extends javax.swing.JFrame {&nbsp; &nbsp; Connection con = null;&nbsp; &nbsp; PreparedStatement pst = null;&nbsp; &nbsp; ResultSet rs = null;&nbsp; &nbsp; public NewJFrame() {&nbsp; &nbsp; &nbsp; &nbsp; initComponents();&nbsp; &nbsp; }&nbsp; &nbsp; @SuppressWarnings("unchecked")&nbsp; &nbsp; // <editor-fold defaultstate="collapsed" desc="Generated Code">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp; &nbsp; private void initComponents() {&nbsp; &nbsp; &nbsp; &nbsp; jPanel1 = new javax.swing.JPanel();&nbsp; &nbsp; &nbsp; &nbsp; jLabel1 = new javax.swing.JLabel();&nbsp; &nbsp; &nbsp; &nbsp; jLabel2 = new javax.swing.JLabel();&nbsp; &nbsp; &nbsp; &nbsp; jLabel3 = new javax.swing.JLabel();&nbsp; &nbsp; &nbsp; &nbsp; jLabel4 = new javax.swing.JLabel();&nbsp; &nbsp; &nbsp; &nbsp; Rollno = new javax.swing.JTextField();&nbsp; &nbsp; &nbsp; &nbsp; fname = new javax.swing.JTextField();&nbsp; &nbsp; &nbsp; &nbsp; lname = new javax.swing.JTextField();&nbsp; &nbsp; &nbsp; &nbsp; address = new javax.swing.JTextField();&nbsp; &nbsp; &nbsp; &nbsp; jButton1 = new javax.swing.JButton();&nbsp; &nbsp; &nbsp; &nbsp; jButton2 = new javax.swing.JButton();&nbsp; &nbsp; &nbsp; &nbsp; jButton3 = new javax.swing.JButton();&nbsp; &nbsp; &nbsp; &nbsp; jButton4 = new javax.swing.JButton();&nbsp; &nbsp; &nbsp; &nbsp; setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);&nbsp; &nbsp; &nbsp; &nbsp; jLabel1.setText("RollNo");&nbsp; &nbsp; &nbsp; &nbsp; jLabel2.setText("First Name");&nbsp; &nbsp; &nbsp; &nbsp; jLabel3.setText("Last Name");&nbsp; &nbsp; &nbsp; &nbsp; jLabel4.setText("Address");&nbsp; &nbsp; &nbsp; &nbsp; jButton1.setText("Insert");&nbsp; &nbsp; &nbsp; &nbsp; jButton1.addActionListener(new java.awt.event.ActionListener() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; public void actionPerformed(java.awt.event.ActionEvent evt) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; jButton1ActionPerformed(evt);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; });&nbsp; &nbsp; &nbsp; &nbsp; jButton2.setText("Update");&nbsp; &nbsp; &nbsp; &nbsp; jButton3.setText("Delete");&nbsp; &nbsp; &nbsp; &nbsp; jButton3.addActionListener(new java.awt.event.ActionListener() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; public void actionPerformed(java.awt.event.ActionEvent evt) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; jButton3ActionPerformed(evt);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; });&nbsp; &nbsp; &nbsp; &nbsp; jButton4.setText("New");&nbsp; &nbsp; &nbsp; &nbsp; javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);&nbsp; &nbsp; &nbsp; &nbsp; jPanel1.setLayout(jPanel1Layout);&nbsp; &nbsp; &nbsp; &nbsp; jPanel1Layout.setHorizontalGroup(&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createSequentialGroup()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addContainerGap(36, Short.MAX_VALUE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createSequentialGroup()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton1)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton2)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton3)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton4))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createSequentialGroup()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel3, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel2, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 69, Short.MAX_VALUE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel4, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(Rollno, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 107, Short.MAX_VALUE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(fname, javax.swing.GroupLayout.Alignment.LEADING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(lname, javax.swing.GroupLayout.Alignment.LEADING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(address))))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addContainerGap(433, Short.MAX_VALUE))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; );&nbsp; &nbsp; &nbsp; &nbsp; jPanel1Layout.setVerticalGroup(&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createSequentialGroup()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGap(29, 29, 29)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel1)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(Rollno, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGap(18, 18, 18)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel2)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(fname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGap(18, 18, 18)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel3)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(lname, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGap(18, 18, 18)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jLabel4)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(address, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGap(27, 27, 27)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton1)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton2)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton3)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jButton4))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addContainerGap(115, Short.MAX_VALUE))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; );&nbsp; &nbsp; &nbsp; &nbsp; javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());&nbsp; &nbsp; &nbsp; &nbsp; getContentPane().setLayout(layout);&nbsp; &nbsp; &nbsp; &nbsp; layout.setHorizontalGroup(&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; );&nbsp; &nbsp; &nbsp; &nbsp; layout.setVerticalGroup(&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; );&nbsp; &nbsp; &nbsp; &nbsp; pack();&nbsp; &nbsp; }// </editor-fold>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp; &nbsp; private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; try{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; String sql = "INSERT INTO persons(fname, lname, address) VALUES (?,?,?)";&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //Class.forName("com.mysql.jdbc.Driver");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; con=DriverManager.getConnection("jdbc:mysql://localhost/test3","root","");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst = con.prepareStatement(sql);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst.setString(1,fname.getText());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst.setString(2,lname.getText());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst.setString(3,address.getText());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst.executeUpdate();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; con.close();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; JOptionPane.showMessageDialog(null, "Insert Successfull");&nbsp; &nbsp; &nbsp; &nbsp; } catch(SQLException | HeadlessException ex){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; JOptionPane.showMessageDialog(null, ex);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp; &nbsp; private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; try{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; String sql = "Delete from test3 where Rollno=?";&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; con=DriverManager.getConnection("jdbc:mysql://localhost/test3","root","");&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst = con.prepareStatement(sql);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst.setString(1,Rollno.getText());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; pst.executeUpdate();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; con.close();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; JOptionPane.showMessageDialog(null, "Delete Successfull");&nbsp; &nbsp; &nbsp; &nbsp; } catch(SQLException | HeadlessException ex){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; JOptionPane.showMessageDialog(null, ex);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp; &nbsp; /**&nbsp; &nbsp; &nbsp;* @param args the command line arguments&nbsp; &nbsp; &nbsp;*/&nbsp; &nbsp; public static void main(String args[]) {&nbsp; &nbsp; &nbsp; &nbsp; /* Set the Nimbus look and feel */&nbsp; &nbsp; &nbsp; &nbsp; //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">&nbsp; &nbsp; &nbsp; &nbsp; /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;*/&nbsp; &nbsp; &nbsp; &nbsp; try {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ("Nimbus".equals(info.getName())) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; javax.swing.UIManager.setLookAndFeel(info.getClassName());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; break;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; } catch (ClassNotFoundException ex) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);&nbsp; &nbsp; &nbsp; &nbsp; } catch (InstantiationException ex) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);&nbsp; &nbsp; &nbsp; &nbsp; } catch (IllegalAccessException ex) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);&nbsp; &nbsp; &nbsp; &nbsp; } catch (javax.swing.UnsupportedLookAndFeelException ex) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; //</editor-fold>&nbsp; &nbsp; &nbsp; &nbsp; /* Create and display the form */&nbsp; &nbsp; &nbsp; &nbsp; java.awt.EventQueue.invokeLater(new Runnable() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; public void run() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; new NewJFrame().setVisible(true);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; });&nbsp; &nbsp; }&nbsp; &nbsp; // Variables declaration - do not modify&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; private javax.swing.JTextField Rollno;&nbsp; &nbsp; private javax.swing.JTextField address;&nbsp; &nbsp; private javax.swing.JTextField fname;&nbsp; &nbsp; private javax.swing.JButton jButton1;&nbsp; &nbsp; private javax.swing.JButton jButton2;&nbsp; &nbsp; private javax.swing.JButton jButton3;&nbsp; &nbsp; private javax.swing.JButton jButton4;&nbsp; &nbsp; private javax.swing.JLabel jLabel1;&nbsp; &nbsp; private javax.swing.JLabel jLabel2;&nbsp; &nbsp; private javax.swing.JLabel jLabel3;&nbsp; &nbsp; private javax.swing.JLabel jLabel4;&nbsp; &nbsp; private javax.swing.JPanel jPanel1;&nbsp; &nbsp; private javax.swing.JTextField lname;&nbsp; &nbsp; // End of variables declaration&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}