通过 setText 将文本设置为标签时，如何解决添加不需要的按钮和文本字段的问题？

Question

I created a program that runs a calculator class if the login credentials input were correct. But, when the login credentials input were wrong unnecessary components, like text field, buttons etc., were added to the panel alongside the label that should display "Wrong Login Credentials"

The error looks like this:

What should I do to fix this? Thanks in advance

Below is my source code.

import java.awt.*;
import java.awt.Font;
import javax.swing.*;
import java.awt.event.*;

public class LoginGUI implements ActionListener{
    
    //Variables
    JTextField tField1, tField2;
    JPasswordField pwField;
    JButton btn1, btn2;
    JLabel label1, label2, label3, label4;
    private ImageIcon bgImage;
    private JLabel img;
    simpleCal Calculator;
    
    public LoginGUI(){
        //Layout
        SpringLayout layout = new SpringLayout();
        bgImage = new ImageIcon(this.getClass().getResource("/assets/loginBG.png"));
        img = new JLabel(bgImage);
        JFrame f = new JFrame("Login");
        f.setSize(1280,800);
        
        
        JPanel p = new JPanel();
        Container contentPane = f.getContentPane();
        p.setLayout(layout);
        p.setBounds(432,155,400,450);
        p.setBackground(new Color(101,168,223,5));img.setSize(1280,800);
        f.add(p);
        //Fonts
        Font font1 = new Font("calibri",Font.BOLD,20);
        Font font2 = new Font("calibri",Font.BOLD,14);
        
        //Label
        label1 = new JLabel("Username:");
        label1.setFont(font1);
        label1.setForeground(new Color(55,55,55));
        layout.putConstraint(layout.WEST, label1, 50, layout.WEST, contentPane);
        layout.putConstraint(layout.NORTH, label1, 130, layout.NORTH, contentPane);
        
        label2 = new JLabel("Password:");
        label2.setFont(font1);
        label2.setForeground(new Color(55,55,55));
        layout.putConstraint(layout.WEST, label2, 50, layout.WEST, contentPane);
        layout.putConstraint(layout.NORTH, label2, 30, layout.SOUTH, label1);
        
        label3 = new JLabel("");
        label3.setFont(font1);
        label3.setForeground(new Color(55,55,55));
        layout.putConstraint(layout.WEST, label3, 105, layout.WEST, contentPane);
        layout.putConstraint(layout.NORTH, label3, 40, layout.NORTH, contentPane);
        
        
        label4 = new JLabel("");
        label4.setFont(font1);
        label4.setForeground(new Color(55,55,55));
        layout.putConstraint(layout.WEST, label4, 105, layout.WEST, contentPane);
        layout.putConstraint(layout.NORTH, label4, 20, layout.SOUTH, label3);
        
        
        //TextField
        tField1 = new JTextField("");
        tField1.setFont(font2);
        tField1.setColumns(15);
        tField1.setBackground(new Color(101,168,223));
        layout.putConstraint(layout.WEST, tField1, 40, layout.EAST, label1);
        layout.putConstraint(layout.NORTH, tField1, 130, layout.NORTH, contentPane);
        
        //PasswordField
        pwField = new JPasswordField();
        pwField.setFont(font2);
        pwField.setColumns(15);
        pwField.setBackground(new Color(101,168,223));
        layout.putConstraint(layout.WEST, pwField, 43, layout.EAST, label2);
        layout.putConstraint(layout.NORTH, pwField, 30, layout.SOUTH, tField1);
        
        //Button
        btn1 = new JButton("Log in");
        btn1.setFont(font1);
        btn1.setSize(100,50);
        btn1.addActionListener(this);
        p.add(btn1);
        layout.putConstraint(layout.WEST, btn1, 80, layout.WEST, contentPane);
        layout.putConstraint(layout.NORTH, btn1, 250, layout.NORTH, contentPane);
        
        
        f.add(img);
        p.add(label3);
        p.add(label4);
        p.add(tField1);
        p.add(pwField);
        p.add(label1);
        p.add(label2);
        
        f.setVisible(true);
        f.setResizable(false);
        f.setLocationRelativeTo(null);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        
    }
    
    public void actionPerformed(ActionEvent e){
        String user, pass;
        
        int i = 0;
        int maxAttempt = 3;
        
        if(e.getSource()==btn1){
            user = tField1.getText();
            pass = pwField.getText();
            
            if(user.equals("vince")&&pass.equals("123")){
                Calculator = new simpleCal();
            }
            else{
                while(i<maxAttempt){
                label3.setText("Wrong Login Credentials");
                i++;
                label4.setText("Attempt: " + i);
                }
            }
        }
        
    }
    
    public static void main(String[]args){
        new LoginGUI();
    }
}

Answer 1

I don't know why you're getting these unnecessary components, but you don't need a while-loop inside your actionPerformed : the first time you enter the wrong credentials, it'll run the loop three times already.

Create these integer fields inside your LoginGUI class:

class LoginGUI {
    private static final int MAX_ATTEMPTS = 3;

    private int currentAttempt = 0;
}

Every time an user try to login, increase currentAttempt inside your actionPerformed and check if it's lesser than MAX_ATTEMPTS :

class LoginGUI {
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == btn1){
            // Don't proceed with the login if the maximum attempt has been reached
            if (currentAttempt == MAX_ATTEMPTS) return;
     
            final String user = tField1.getText();
            final String pass = pwField.getText();
             
            if (user.equals("vince") && pass.equals("123")) {
                Calculator = new simpleCal();
            
            } else {
                // Increase the current attempt counter
                currentAttempt += 1;
    
                // Display it in the JLabels
                if (currentAttempt == MAX_ATTEMPTS) {
                    label3.setText("Your login attempts have been expired");
                } else {
                    label3.setText("Wrong Login Credentials");
                }
                label4.setText("Attempt: " + currentAttempt);
            }
        }
    }
}