Notes

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;

public class MainPage extends JFrame {

JFrame frame = new JFrame();
int updateId;

MainPage() {
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.setSize(420, 420);
frame.setLayout(null);
frame.setVisible(true);

JLabel label = new JLabel("Ene bol undsen huudas");
label.setBounds(80, 24, 140, 25);
frame.add(label);

JScrollPane sp = new JScrollPane();
sp.setBounds(10, 64, 366, 107);
frame.add(sp);

JTextField username = new JTextField();
username.setBounds(10, 200, 100, 30);
frame.add(username);

JTextField emaile = new JTextField();
emaile.setBounds(10, 280, 100, 30);
frame.add(emaile);

JButton updateBTN = new JButton("Update");
updateBTN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
updateData(username.getText(), emaile.getText());
}
});
frame.add(updateBTN);
updateBTN.setBounds(200, 300, 89, 23);

JButton deleteBTN = new JButton("Delete");
deleteBTN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
deleteData();
}
});
frame.add(deleteBTN);
deleteBTN.setBounds(300, 300, 89, 23);

loadTableData(sp);

}

private void loadTableData(JScrollPane sp) {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/sarnai", "root", "");
Statement stmt = con.createStatement();
String sql = "SELECT * FROM users";
ResultSet rs = stmt.executeQuery(sql);
String[] column = { "ID", "Name", "Email" };
DefaultTableModel tdm = new DefaultTableModel(column, 0);
while (rs.next()) {
String id = rs.getString("u_id");
String uname = rs.getString("username");
String email = rs.getString("email");

String[] data = { id, uname, email };
tdm.addRow(data);
}

JTable jt = new JTable(tdm);
sp.setViewportView(jt);

jt.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent me) {
int row = jt.getSelectedRow();
if (row < 0) {
System.out.print("Didn't select any row");
} else {
updateId = Integer.parseInt(jt.getValueAt(row, 0).toString());
username.setText(jt.getValueAt(row, 1).toString());
emaile.setText(jt.getValueAt(row, 2).toString());
}
}
});

} catch (Exception e) {
System.out.print(e);
}
}

private void updateData(String username, String email) {
if (updateId == 0) {
JOptionPane.showMessageDialog(null, "Please select a user to update");
return;
}
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/sarnai", "root", "");
String sql = "UPDATE users SET username = ?, email = ? WHERE u_id = ?";
PreparedStatement pstmt = con.prepareStatement(sql);
pstmt.setString(1, username);
pstmt.setString(2, email);
pstmt.setInt(3, updateId);
pstmt.executeUpdate();
JOptionPane.showMessageDialog(null, "User updated successfully");
con.close();
frame.dispose();
new MainPage();
} catch (Exception e) {
System.out.print(e);
}
}

private void deleteData() {
if (updateId == 0) {
JOptionPane.showMessageDialog(null, "Please select a user to delete");
return;
}
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/sarnai", "root", "");
String sql = "DELETE FROM users WHERE u_id = ?";
PreparedStatement pstmt = con.prepareStatement(sql);
pstmt.setInt(1, updateId);
pstmt.executeUpdate();
JOptionPane.showMessageDialog(null, "User deleted successfully");
con.close();
frame.dispose();
new MainPage();
} catch (Exception e) {
System.out.print(e);
}
}

public static void main(String[] args) {
new MainPage();
}
}