Connection to MySQL from a JFrame

Question

I want to connect to MySQL using a JFrame but the program is telling me "error while establishing connection"

This is what I tried:

These are the declaration I did before writing the code below:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;

This is the code I use for the connection:

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
   String un= user.getText();
   String p= pass.getText();
    
   try{
       Class.forName("com.mysql.jdbc.Driver");
            Connection conn= (Connection) DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/sms","root","");
            Statement st= (Statement)conn.createStatement();
            String sql= "select * from user_login";
             
             ResultSet rs= st.executeQuery(sql);
             while(rs.next()){
                  String username= rs.getString("username");
                  String Password= rs.getString("password");
           if(un.equals(username) && p.equals(Password)){
                    new welcome().setVisible(true);
        }
            else
        {
            JOptionPane.showMessageDialog(this, "Username or Password is incorrect!");
        }
             }
           
       } 
   catch(Exception e){
        JOptionPane.showMessageDialog(null, "Error while establishing connection");
    }

Expecting to be connected using this code but the program is telling me "error while establishing connection"