Mysql – Having Error message connection is null while the database is connected

I created a utility class to handle database connections using JDBC. I get the error below in another class, performing actions such as displaying the values from the database:

"Cannot invoke "java.sql.Connection.prepareStatement(String)" because "Utils.connection" is null"

I have another class where the connection works like a charm.

//// This is the connection class.

import java.sql.*;

public class Utils { 

    public static Connection connection ; 
    public static PreparedStatement preStmt;
    public static ResultSet rs;

    public static  void Connect() {
        try {
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/testdb", "root", "");      
            System.out.println("DataBase Connected ;)");

        } catch (SQLException e) { 
            throw new RuntimeException(e); 
        } 
    }
} 

/////// This is the other class where I get the error message

import javax.swing.*;
import java.sql.SQLException;

public class Contacts {

    static JFrame frame = new JFrame("Contacts");
    private JButton searchButton;
    private JTextField textSearch;
    private JList list;
    private JButton createButton;
    private JButton deleteButton;
    private JButton editButton;
    private JPanel Main;
    private DefaultListModel<String> listModel;

    public static void main(String[] args) {
        frame.setContentPane(new Contacts().Main);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.setResizable(false);
        frame.setSize(500, 700);

        Utils.Connect();
    }

    public Contacts() {
        DefaultListModel<String> listModel = new DefaultListModel<>();
        list.setModel(listModel);

        loadContacts(); 
    }

    public void loadContacts() { 
        String name;
        String number;
        String address;

        listModel.clear();

        try {
            Utils.preStmt = Utils.connection
                .prepareStatement("SELECT * FROM contactsdb WHERE id =?");     
            Utils.preStmt.setString(1, String.valueOf(list)); 
            Utils.rs = Utils.preStmt.executeQuery();

            while (Utils.rs.next()) {
                name = Utils.rs.getString(1);
                number = Utils.rs.getString(2);
                address = Utils.rs.getString(3);
                listModel.addElement(name + " " + number + " " + address);
                listModel.addElement(number); listModel.addElement(address); 
            } 
        } catch (SQLException e) {
            e.printStackTrace(); 
        } 
    }   
}