MySql and Java and Query

Question: Can you take text that has been input through a textbox assign it to a 'String name;' then take that String call a separate class that actually holds the connection to the MySql database and also the query you want to run and pass it that string value to fulfill a query parameter? Now I know enough that passing values from one class to another is not unusual but it appears that I may be missing a piece to properly pass the string to the query properly.

I am connecting properly so I will not include all of that information:

 
Public class Mediator{
public Boolean verifyLogin(String un, String pw){

        Boolean compareValue = false;
        String sql = "select * from users where login_Name = ? and password = ?";

        try {
            pst = conn.prepareStatement(sql);
            pst.setString(1, un);
            pst.setString(2, pw);
            rs = pst.executeQuery();
            
            
            while (rs.next()) {
                compareValue = true;
                //JOptionPane.showMessageDialog(null, "username and password are correct");
                //Added this line so when login is successful the StartupScreen.java will initialize.
                //new StartupScreen().setVisible(true);
            }
        }
        catch (Exception e) {
            //JOptionPane.showMessageDialog(null, e);
        }

       return compareValue;

    }
}

This is the method that is initially accepting the input from the textbox.

public class LoginScreenFrom{} {
 private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        
        String userName = username.getText();
        String passWord = password.getText();
        if (mediator.verifyLogin(userName, passWord)){
       
        // transition to next page
        }
        else{JOptionPane.showMessageDialog(null, "Invalid username and password");}

This is just the two methods that I am concerned with at this point. I am looking to simply see how to pass the values properly...since this is not working as it is right now.