Converting a console interface to GUI in java

Question

I am trying to change a console-based interface for a parking system to a GUI based one. I am using Swing and I have created a GUI class G that will act as the main menu of the new system. This is what I have so far:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.GraphicsConfiguration;
public class G extends javax.swing.JFrame {
    
    G(){    
        JFrame f=new JFrame("Parking System"); 
        
                    //submit button
        JButton b=new JButton("Confirm"); 
        
        b.setBounds(600,500,100, 40); 
        JButton b1 = new JButton("Back");
        
                    //enter name label
        JLabel label = new JLabel();        
        label.setText("Please enter number of slots for staff:");
        label.setBounds(10, 10, 400, 100);
        JTextField textfield1= new JTextField();
        textfield1.setBounds(280, 50, 50, 20);
        textfield1.setHorizontalAlignment(JTextField.CENTER);
                    //empty label which will show event after button clicked
        JLabel label1 = new JLabel();
        label1.setText("Please enter number of slots for visitor:");
        label1.setBounds(10, 210, 400, 100);
        JTextField textfield2 = new JTextField();
        textfield2.setBounds(280, 250, 50, 20); 
        textfield2.setHorizontalAlignment(JTextField.CENTER);
        
        JLabel label3 = new JLabel();
        
    
        JLabel label2 = new JLabel();
        
        JLabel label4= new JLabel();
        label4.setText("The slots for visitor have been created");
        
        JLabel menu = new JLabel();
        JLabel lab1= new JLabel();
        JLabel lab2 = new JLabel();
        JLabel lab3 = new JLabel();
        JLabel lab4 = new JLabel();
        JLabel lab5 = new JLabel();
        JLabel lab6 = new JLabel();
        
        JLabel lab7 = new JLabel();
        JLabel lab8 = new JLabel();
        
        JButton in = new JButton();
        JTextField textfield3 = new JTextField();
        textfield3.setHorizontalAlignment(JTextField.CENTER);
        
        //textfield to enter name
        
                    //add to frame
        f.add(label);
        f.add(textfield1);
        f.add(label1);
        f.add(label2);
        f.add(label3);
        f.add(textfield2);
        f.add(label2);
        f.add(menu);
        f.add(lab1);
        f.add(lab2);
        f.add(lab3);
        f.add(lab4);
        f.add(lab5);
        f.add(lab6);
        f.add(lab7);
        f.add(lab8);
        f.add(in);
        f.add(textfield3);
        
        f.add(b);   
        f.add(b1);
        f.setSize(800,600);    
        f.setLayout(null);    
        f.setVisible(true);    
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);   
        
                            //action listener
        b.addActionListener(new ActionListener() {
            
            @Override
            public void actionPerformed(ActionEvent e) {
                   label.setText(textfield1.getText());
                   textfield1.setBounds(280, 50, 0, 0);
                   label1.setText("slots for staff are created successfully");
                   label1.setBounds(30, 10, 400, 100);
                   label3.setText(textfield2.getText());
                   label3.setBounds(10, 30,50,100);
                   textfield2.setBounds(280,50,0,0);
                   label2.setText("slots for visitors are created successfully");
                  label2.setBounds(30, 30, 400,100);
                  
                  menu.setBounds(10, 60, 400,100);
                  menu.setText("Main Menu");
                  
                  lab1.setText("1: List all car slots");
                  lab1.setBounds(10, 80, 400, 100);
                  lab2.setText("2: Park a car");
                  lab2.setBounds(10, 120, 400, 100);
                  lab3.setText("3: Find a car");
                  lab3.setBounds(10, 160, 400, 100);
                  lab4.setText("4: Remove a car");
                  lab4.setBounds(10, 200, 400, 100);
                  lab5.setText("5: Add a car");
                  lab5.setBounds(10, 240, 400, 100);
                  lab6.setText("6: Delete a car slot");
                  lab6.setBounds(10, 280, 400, 100);
                  lab7.setText("7: Exit");
                  lab7.setBounds(10, 320, 400, 100);
                  lab8.setText("Please select an option from (1-7)");
                  lab8.setBounds(10, 360,400,100);
                  textfield3.setBounds(240, 402, 30, 20);
                  
                  b1.setBounds(100,500,100,40);
                  
                  
                  
                  
                   
            }          
          });
               
        }         
    
   
        public static void main(String[] args) {    
            new G();  
            
            
            
 }
}

From the initial console-based interface, I have the CarPark class which is responsible for maintaining a list of available parking slots. This is a part of the CarPark class

import java.util.*;

public class CarPark {
    private Map<String, String> staffParking = new HashMap<String, String>();
    private Map<String, String> visitorParking = new HashMap<String, String>();
    private static int s_slots;
    private static int v_slots;
    private static int nextStaffSlot = 1;
    private static int nextVisitorSlot = 1;
    private List<ParkingSlot> slotInfos = new ArrayList<ParkingSlot>();
    
    CarPark( int v_slot, int s_slot) {
        v_slots = v_slot;
        s_slots = s_slot;
        int number = 1;
        
        for (int i=0; i<v_slots; i++) {
            String slot = "V" + String.format("%03d", number++);
            visitorParking.put(slot, "not occupied");
        }
        number = 1;
        for (int j = 0; j<s_slots; j++) {
            String slot = "S" + String.format("%03d", number++);
            staffParking.put(slot, "not occupied");
        }
    }
    public void getSlots() {
        for (Map.Entry<String, String> id : staffParking.entrySet()) { 
            System.out.print("SlotID is: "+id.getKey() + ", is for staff, "); 
            System.out.println("and is "+id.getValue()); 
        } 
        for (Map.Entry<String, String> id : visitorParking.entrySet()) { 
            System.out.print("SlotID is: "+id.getKey() + ", is for visitor, "); 
            System.out.println("and is "+id.getValue()); 
        } 
    }
    private boolean validRego(String carNum) { //validate car registration
        
        if (!Character.isUpperCase(carNum.charAt(0))) {
        
            return false;
        }
        for(int i=1;i<carNum.length();i++) { //use ascii values to check if valid
            if(!(carNum.charAt(i)>47 && carNum.charAt(i)<58)) {
                return false;
            }
            else if ((carNum.length()>6) || (carNum.length()<6) ){
                return false;}
        }
        
        return true;
    }
    
    
    
    public void parking() { //enter parking info
        System.out.println("Enter S for staff parking or V for visitor parking ");
        Scanner in = new Scanner(System.in);
        char slotType = in.next().charAt(0);
        ParkingSlot slotInfo;
        if(slotType == 'V') { //for visitor 
            if(nextVisitorSlot<=v_slots) {
                System.out.println("Please enter slot number:");
                String slot_num = in.next();
                if(!(visitorParking.containsKey(slot_num))) {
                    System.out.println("Enter valid slot number!"); 
                }
                else {
                
                System.out.println("Please enter car registration number:");
                String c_number = in.next();    
                if(validRego(c_number)) {
                    System.out.println("Enter owner's name: ");
                    String owner = in.next();
                           
                    if(visitorParking.containsKey(slot_num)) {
                        if(visitorParking.get(slot_num) != "occupied") {
                            nextVisitorSlot++;
                            visitorParking.put(slot_num,"occupied");
                            slotInfo = new VisitorParkingSlot(c_number,owner,slot_num);
                            slotInfos.add(slotInfo);
                            System.out.println("Car successfully added!");
                        }
                        else {
                            System.out.println("The slot is already occupied");
                        }
                        
                    }
                    
                    
                }else {
                    System.out.println("Enter valid car registration number.");
                }
            }
        }
            else {
                System.out.println("All Visitor parking slots are occupied.");
            }
        }
        else if(slotType == 'S') { //for staff 
             if(nextStaffSlot<=s_slots) {
                System.out.println("Enter the slot number:");
                String slot_num = in.next();
                if(!(staffParking.containsKey(slot_num))) {
                    System.out.println("Enter valid slot number!"); 
                }
                else {
                System.out.println("Enter the car number:");
                String c_number = in.next();
                if(validRego(c_number)) {
                    System.out.println("Enter owner's name");
                    String owner = in.next();
                    if(staffParking.containsKey(slot_num)) {
                        if(staffParking.get(slot_num)!="occupied") {
                            nextStaffSlot++;
                            staffParking.put(slot_num,"occupied");
                            slotInfo = new StaffParkingSlot(c_number,owner,slot_num);
                            slotInfos.add(slotInfo);
                            System.out.println("Car successfully added!");
                        }else {
                            System.out.println("The slot is already occupied");
                        }
                        
                    }
                    
                }else {
                    System.out.println("Enter valid car registration number.");
                }
                
            }
        }
            else {
                System.out.println("All Staff parking slots are occupied.");
            }
            
        }
        else {
            System.out.println("Parking slots must start with S or V!");
        }
    }
}

My question is how can I link the GUI class G with the CarPark class so that if the user for example enters 1 into textfield3, the method getSlots is called or if the user enters 2, the method parking is called and the code inside the methods is executed and the output inside the methods is displayed in the GUI window when the confirm button is clicked. I am new to GUI so I have been looking up tutorials so far but I haven't found anything to help me with this issue. Any help would be appreciated!

Answer 1

The question is quiet broad. I'll try to outline a rough roadmap.
The first thing to do is to sperate UI from data. To do that add a class that its sole purpose it to hold all the data (and some logic) that is required by the UI.
Such class is typically referred to as model class. Let's call it CarParkModel.
To demonstrate the idea consider a very basic CarPark that only creates a number of parking slots and shows the number of free slots:

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class CarPark {

    private final CarParkModel model;

    CarPark() {

        model = new CarParkModel();
         Scanner in = new Scanner(System.in);
         int parkingSlot = 0;
         while(true){
             System.out.println("Please enter valid number of parking slots <1-5>: ");
             parkingSlot = in.nextInt();
             if(parkingSlot>0 && parkingSlot<6) {
                break;
            }
         }
         
        for (int i=0; i<parkingSlot; i++) {
            model.addStaffParking(true);
        }
    }

    public int freeParkings() {
        return model.freeParkings();
    }

    public static void main(String[] args) {
        CarPark cp = new CarPark();
        System.out.println("number of free slots is " + cp.freeParkings());
    }
}

class CarParkModel{

    private final List<String> parking = new ArrayList<>();
    private final static String OCCUPIED = "occupied", FREE = "free";

    void addStaffParking(boolean isFree){
        if(isFree){
            parking.add(FREE);
        }else{
            parking.add(OCCUPIED);
        }
    }

    int freeParkings(){
        int numberOfFreeParkings = 0;
        for(String s : parking){
            if(s.equals(FREE)) {
                numberOfFreeParkings++;
            }
        }
        return numberOfFreeParkings;
    }
}  

Next step would be creating a GUI, using the very same model. This is why we separate the data (model) from the view (UI).
When you build swing gui, do not set bounds. Use layout managers .