java swing layout-manager gridbaglayout jradiobutton

JRadioButton is not show properly

I want to create a simple food ordering system, now i'm creating the interface of an order form. I used GridBagLayout for create the form layout, my problem is when I want to assign 3 radio button in same row, it's only show me 1 of the button....I hope somebody can help me pls....

Here is my java code:

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.*;

/**
 *
 * @author user
 */
public class ChickenChopOrderingSystem
{
    JFrame frame;
    JPanel mainPanel, p1, p2, p3, p4;
    JLabel lblTitle, lblName, lblPhoneNum, lblFlavour, lblChickenPart;
    JTextField txtName, txtPhoneNum;
    String flavour[] = {"Black Pepper Sauce", "Hainanese", "Grilled", "Lemon"};
    JComboBox box;
    ButtonGroup bg = new ButtonGroup();
    JRadioButton btnWhole, btnHalf, btnQuarter;
    JButton btnDone, btnExit;

    public ChickenChopOrderingSystem()
    {
        frame = new JFrame("Chicken Chop Ordering System");
        mainPanel = new JPanel();
        mainPanel.setPreferredSize(new Dimension(700,700));
        mainPanel.setBackground(Color.yellow);

        lblName = new JLabel("Customer's Name: ");
            txtName = new JTextField(20);

        lblPhoneNum = new JLabel("Phone Number: ");
            txtPhoneNum = new JTextField(11);

        lblChickenPart = new JLabel("Select Part of Chicken: ");
            btnWhole = new JRadioButton("Whole");
                btnWhole.addItemListener(new OperationListener());
            btnHalf = new JRadioButton("Half");
                btnHalf.addItemListener(new OperationListener());
            btnQuarter = new JRadioButton("Quarter");
                btnQuarter.addItemListener(new OperationListener());
            bg.add(btnWhole);
            bg.add(btnHalf);
            bg.add(btnQuarter);

        lblFlavour = new JLabel("Select a flavour: ");
            box = new JComboBox(flavour);

        btnDone = new JButton("Done");
        btnExit = new JButton("Exit");
            btnExit.addActionListener(new ButtonListener());

        //GridBaglayout
        mainPanel.setLayout(new GridBagLayout()); 
        GridBagConstraints gbc = new GridBagConstraints();

        //Label
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.weightx = 0.5;
        gbc.weighty = 0.5;
        mainPanel.add(lblName, gbc);


        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.weightx = 0.5;
        mainPanel.add(lblPhoneNum, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.weightx = 0.5;        
        mainPanel.add(lblChickenPart, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 3;
        gbc.weightx = 0.5;
        mainPanel.add(lblFlavour, gbc);

        //TextField
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 0;
        gbc.gridwidth = 3;
        mainPanel.add(txtName, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 1;
        gbc.gridwidth = 3;
        mainPanel.add(txtPhoneNum, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 2;
        mainPanel.add(btnWhole, gbc);

        gbc.gridx = 2;
        gbc.gridy = 2;
        mainPanel.add(btnHalf, gbc);

        gbc.gridx = 3;
        gbc.gridy = 2;
        mainPanel.add(btnHalf, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 3;
        mainPanel.add(box, gbc);


        //frame setting
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new GridBagLayout());
        frame.add(mainPanel, new GridBagConstraints());
        frame.setSize(new Dimension(1000, 1000));
        frame.setVisible(true);
    }


    public class OperationListener implements ItemListener
    {
        @Override
        public void itemStateChanged(ItemEvent ie) {
            if (ie.getSource() == btnWhole) 
            {                 
                if (ie.getStateChange() == ItemEvent.SELECTED) 
                {   
                    box.removeAllItems(); 
                    box.addItem(flavour[2]);
                }


            } if (ie.getSource() == btnHalf)
            {                 
                if (ie.getStateChange() == ItemEvent.SELECTED) 
                {   
                    box.removeAllItems(); 
                    box.addItem(flavour[0]);
                    box.addItem(flavour[2]);
                    box.addItem(flavour[3]);
                }

            } if (ie.getSource() == btnQuarter)
            {
                if (ie.getStateChange() == ItemEvent.SELECTED) 
                {   
                    box.removeAllItems(); 
                    box.addItem(flavour[0]);
                    box.addItem(flavour[1]);
                    box.addItem(flavour[3]);              
                }
            }
        }
    }

    public class ButtonListener implements ActionListener
    {
        @Override

        public void actionPerformed(ActionEvent ae) {
            if (ae.getSource() == btnExit)
            {
                int s = JOptionPane.showConfirmDialog(null, "Are you sure you want to exit?",              
                    "Exit", JOptionPane.YES_NO_OPTION);      

                if (s == JOptionPane.YES_OPTION) 
                {            
                    System.exit(0);         
                } 
            }
        }

    }

    public static void main(String[] args)
    {
        ChickenChopOrderingSystem run = new ChickenChopOrderingSystem();
    }
}

Click here to view output

Solution

For something like this:

Use this code:

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

public class ChickenChopOrderingSystem {

    JFrame frame;
    JPanel mainPanel, p1, p2, p3, p4;
    JLabel lblTitle, lblName, lblPhoneNum, lblFlavour, lblChickenPart;
    JTextField txtName, txtPhoneNum;
    String flavour[] = {"Black Pepper Sauce", "Hainanese", "Grilled", "Lemon"};
    JComboBox box;
    ButtonGroup bg = new ButtonGroup();
    JRadioButton btnWhole, btnHalf, btnQuarter;
    JButton btnDone, btnExit;

    public ChickenChopOrderingSystem() {
        frame = new JFrame("Chicken Chop Ordering System");
        mainPanel = new JPanel();
        // GUESSWORK! 
        //mainPanel.setPreferredSize(new Dimension(700,700));
        mainPanel.setBackground(Color.yellow);

        lblName = new JLabel("Customer's Name: ");
        txtName = new JTextField(20);

        lblPhoneNum = new JLabel("Phone Number: ");
        txtPhoneNum = new JTextField(11);

        lblChickenPart = new JLabel("Select Part of Chicken: ");
        btnWhole = new JRadioButton("Whole");
        btnHalf = new JRadioButton("Half");
        btnQuarter = new JRadioButton("Quarter");
        bg.add(btnWhole);
        bg.add(btnHalf);
        bg.add(btnQuarter);

        lblFlavour = new JLabel("Select a flavour: ");
        box = new JComboBox(flavour);

        btnDone = new JButton("Done");
        btnExit = new JButton("Exit");

        //GridBaglayout
        mainPanel.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        int s = 20;
        gbc.insets = new Insets(s,s,s,s);

        //Label
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.weightx = 0.5;
        gbc.weighty = 0.5;
        mainPanel.add(lblName, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.weightx = 0.5;
        mainPanel.add(lblPhoneNum, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.weightx = 0.5;
        mainPanel.add(lblChickenPart, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 0;
        gbc.gridy = 3;
        gbc.weightx = 0.5;
        mainPanel.add(lblFlavour, gbc);

        //TextField
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 0;
        gbc.gridwidth = 3;
        mainPanel.add(txtName, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 1;
        gbc.gridwidth = 3;
        mainPanel.add(txtPhoneNum, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 2;
        gbc.gridwidth = 1;
        gbc.weightx = 1d/6d;
        mainPanel.add(btnWhole, gbc);

        gbc.gridx = 2;
        gbc.gridy = 2;
        mainPanel.add(btnHalf, gbc);

        gbc.gridx = 3;
        gbc.gridy = 2;
        mainPanel.add(btnQuarter, gbc);

        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridx = 1;
        gbc.gridy = 3;
        gbc.gridwidth = 3;
        mainPanel.add(box, gbc);

        //frame setting
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new GridBagLayout());
        frame.add(mainPanel, new GridBagConstraints());
        // GUESSWORK! 
        //frame.setSize(new Dimension(1000, 1000));
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        ChickenChopOrderingSystem run = new ChickenChopOrderingSystem();
    }
}

The problems in the original code were many. (Trawling memory..)

The constraints of the last element were not set back to grid width of 3, confusing the layout manager.
The ItemListener was doing strange stuff with removing components, don't do that.
The preferred size of the panel, and the size of the frame, were guesswork. Use pack() to have the correct size calculated. (Add a standard Inserts to the initial constraints for white space.)