How to make this text area show which toggle buttons are selected?

Please can someone help me, I'm trying to make a seat reservation part for my cinema ticket system assignment ... so the problem is i want the text of the button to show in the text area when selected and not show only the specific text when deselected .. but when i deselect a button the whole text area is cleared.

For e.g. when I select C1, C2, C3 - it shows in the text area correctly, but if I want to deselect C3, the text area must now show only C1 & C2. Instead, it clears the whole text area!

Can anyone spot the problem in the logic?

  import java.awt.*;
  import static java.awt.Color.blue;
  import javax.swing.*;
  import java.awt.event.*;
  import javax.swing.border.Border;


  public class Cw_Test2  extends JFrame {

JButton btn_payment,btn_reset;
JButton buttons;
JTextField t1,t2; 



public static void main(String[] args) {
    // TODO code application logic here
   new  Cw_Test2();
}

public Cw_Test2()
{
    Frame(); 

}

  public void Frame()
{
    this.setSize(1200,700);     //width, height
    this.setTitle("Seat Booking");
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setLocationRelativeTo(null);

    Font myFont = new Font("Serif", Font.ITALIC | Font.BOLD, 6);
    Font newFont = myFont.deriveFont(20F);

    t1=new JTextField();  
    t1.setBounds(15, 240, 240,30); 

    JPanel thePanel = new JPanel()
     {
        @Override
         public Dimension getPreferredSize() {
         return new Dimension(350, 350);
        };
    };    
    thePanel.setLayout(null);

    JPanel ourPanel = new JPanel()        
    {
        @Override
         public Dimension getPreferredSize() {
         return new Dimension(350, 350);
        };
    };
    //ourPanel.setBackground(Color.green);
    Border ourBorder = BorderFactory.createLineBorder(blue , 2);
    ourPanel.setBorder(ourBorder);
    ourPanel.setLayout(null);
    ourPanel.setBounds(50,90, 1100,420); 

    JPanel newPanel = new JPanel()        
    {
        @Override
         public Dimension getPreferredSize() {
         return new Dimension(350, 350);
        };
    };
    //ourPanel.setBackground(Color.green);
    Border newBorder = BorderFactory.createLineBorder(blue , 1);
    newPanel.setBorder(newBorder);
    newPanel.setLayout(null);
    newPanel.setBounds(790,50, 270,340); 

    JLabel label1 = new JLabel( new ColorIcon(Color.GRAY, 400, 100) );
    label1.setText( "SCREEN" );
    label1.setHorizontalTextPosition(JLabel.CENTER);
    label1.setVerticalTextPosition(JLabel.CENTER);
    label1.setBounds(130,50, 400,30);

    JLabel label2 = new JLabel(" CINEMA TICKET MACHINE ");
    label2.setBounds(250,50,400,30);
    label2.setFont(newFont);
    JLabel label3 = new JLabel("Please Select Your Seat");
    label3.setBounds(270,10,500,30);
    label3.setFont(newFont);
    JLabel label4 = new JLabel("Selected Seats:");
    label4.setBounds(20,10,200,30);
    label4.setFont(newFont);


    btn_payment=new JButton("PROCEED TO PAY");  
    btn_payment.setBounds(35,290,200,30);

    JLabel label6 = new JLabel("Center Stall");
   label6.setBounds(285,172,200,30);

     JPanel seatPane, seatPane1, seatPane2, seatPane3, seatPane4, seatPane5;
      JToggleButton[] seat2 = new JToggleButton[8];

    JTextArea chosen = new JTextArea();
 chosen.setEditable(false);
 chosen.setLineWrap(true);
 chosen.setBounds(20, 60, 200, 100); 

  // Center Seats
 seatPane1 = new JPanel();
 seatPane1.setBounds(200,200,250,65);
 seatPane1.setLayout(new FlowLayout());

 for(int x=0; x<8; x++){


     seat2[x] = new JToggleButton("C"+(x+1));


     seatPane1.add(seat2[x]);


    seat2[x].addActionListener(new ActionListener(){

        public void actionPerformed(ActionEvent ev){

            AbstractButton abstractButton = (AbstractButton) ev.getSource();
            boolean selected = abstractButton.getModel().isSelected();

            for(int x=0; x<8; x++){


            if(seat2[x]==ev.getSource()){
                if(selected){


                    chosen.append(seat2[x].getText()+",");


                }else{
                    chosen.setText(seat2[x].getText().replace(seat2[x].getText(),""));





                }



            }

            }

        }

    }); 
 }

 newPanel.add(chosen);
 ourPanel.add(seatPane1);
 ourPanel.add(label6);
 thePanel.add(label2);
    ourPanel.add(label3);
    ourPanel.add(label1);
    newPanel.add(btn_payment);
    newPanel.add(label4);

    ourPanel.add(newPanel);
    thePanel.add(ourPanel);
    add(thePanel);
    setResizable(false);
    this.setVisible(true);

}


  public static class ColorIcon implements Icon
{
    private Color color;
    private int width;
    private int height;

    public ColorIcon(Color color, int width, int height)
    {
        this.color = color;
        this.width = width;
        this.height = height;
    }

    public int getIconWidth()
    {
        return width;
    }

    public int getIconHeight()
    {
        return height;
    }

    public void paintIcon(Component c, Graphics g, int x, int y)
    {
        g.setColor(color);
        g.fillRect(x, y, width, height);
    }
}

When any seat is selected or deselected, this code iterates an array of seats (in the method showSelectedSeats()) and updates the text area to show the seats that are selected.

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

public class CinemaTicketMachine {

    private JComponent ui = null;
    private JToggleButton[] seats = new JToggleButton[80];
    private JTextArea selectedSeats = new JTextArea(3, 40);

    CinemaTicketMachine() {
        initUI();
    }

    public void initUI() {
        if (ui!=null) return;

        ui = new JPanel(new BorderLayout(4,4));
        ui.setBorder(new EmptyBorder(4,4,4,4));

        selectedSeats.setLineWrap(true);
        selectedSeats.setWrapStyleWord(true);
        selectedSeats.setEditable(false);
        ui.add(new JScrollPane(selectedSeats), BorderLayout.PAGE_END);

        JPanel cinemaFloor = new JPanel(new BorderLayout(40, 0));
        cinemaFloor.setBorder(new TitledBorder("Available Seats"));
        ui.add(cinemaFloor, BorderLayout.CENTER);
        JPanel leftStall = new JPanel(new GridLayout(0, 2, 2, 2));
        JPanel centerStall = new JPanel(new GridLayout(0, 4, 2, 2));
        JPanel rightStall = new JPanel(new GridLayout(0, 2, 2, 2));

        cinemaFloor.add(leftStall, BorderLayout.WEST);
        cinemaFloor.add(centerStall, BorderLayout.CENTER);
        cinemaFloor.add(rightStall, BorderLayout.EAST);

        ActionListener seatSelectionListener = new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                showSelectedSeats();
            }
        };

        for (int ii=0; ii <seats.length; ii++) {
            JToggleButton tb = new JToggleButton("S-" + (ii+1));
            tb.addActionListener(seatSelectionListener);
            seats[ii] = tb;
            int colIndex = ii%8;
            if (colIndex<2) {
                leftStall.add(tb);
            } else if (colIndex<6) {
                centerStall.add(tb);
            } else {
                rightStall.add(tb);
            }
        }
    }

    private void showSelectedSeats() {
        StringBuilder sb = new StringBuilder();
        for (int ii=0; ii<seats.length; ii++) {
            JToggleButton tb = seats[ii];
            if (tb.isSelected()) {
                sb.append(tb.getText());
                sb.append(", ");
            }
        }
        String s = sb.toString();
        if (s.length()>0) {
            s = s.substring(0, s.length()-2);
        }
        selectedSeats.setText(s);
    }

    public JComponent getUI() {
        return ui;
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                CinemaTicketMachine o = new CinemaTicketMachine();

                JFrame f = new JFrame(o.getClass().getSimpleName());
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                f.setLocationByPlatform(true);

                f.setContentPane(o.getUI());
                f.pack();
                f.setMinimumSize(f.getSize());

                f.setVisible(true);
            }
        };
        SwingUtilities.invokeLater(r);
    }
}