Mengapa JPanel Saya Tidak Kemas Kini dalam Permainan Teka-teki Swing Saya dan Bagaimana Saya Boleh Membetulkannya Menggunakan `revalidate()`?

public void addComponents(Img[] im){
    this.removeAll();
    for(int i=0; i<16; i++){
        im[i].addActionListener(this);
        im[i].setPreferredSize(new Dimension(53,53));
        add(im[i]);
    }
    this.revalidate();
}

import javax.swing.*;
import java.util.Random;
import java.awt.event.*;
import java.awt.*;

class Puzzle extends JPanel implements ActionListener {
    private int selected_nr=-1;
    private int selected_pl=-1;
    private boolean memory=false;
    private static Img[] images;

    public Puzzle(){
        JFrame f = new JFrame("Smile");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.setSize(252,252);
        f.setVisible(true);

        setLayout(new GridLayout(4, 4));
        images = new Img[16];
        int[] buttons = new int[16];

        for(int i=0; i<16; i++){
            buttons[i] = i;
        }

        int rand;
        int temp;
        Random random;

        random = new Random(System.currentTimeMillis());
        for (int i = 0; i < buttons.length; i++) {
            rand = (random.nextInt() &amp; 0x7FFFFFFF) % buttons.length;
            temp = buttons[i];
            buttons[i] = buttons[rand];
            buttons[rand] = temp;
        }

        for (int i = 0; i < 16; i++) {
            images[i] = new Img(i, buttons[i]);
        }
        addComponents(images);
    }

    public void addComponents(Img[] im){
        this.removeAll();
        for(int i=0; i<16; i++){
            im[i].addActionListener(this);
            im[i].setPreferredSize(new Dimension(53,53));
            add(im[i]);
        }
        this.revalidate();
    }

    public void actionPerformed(ActionEvent e) {
        Img b = (Img)(e.getSource());
        int num = b.getNumber();
        int pl = b.getPlace();

        if(!(b.rightPlace())){
            if(memory){
                if(pl == selected_nr){
                    images[pl].setPlace(selected_pl);
                    images[selected_pl].setPlace(selected_nr);
                    selected_nr = -1;
                    selected_pl = -1;
                    memory = false;
                    addComponents(images);
                }
                else{
                    System.out.println("Try other image");
                }
            }
            else{
                memory = true;
                selected_nr = num;
                selected_pl = pl;
            }
        }
        else{
            System.out.println("OK !");
        }
    }

    public static void main(String args[]) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new Puzzle();
            }
        });
    }
}

class Img extends JButton {
    int number;
    int place;
    ImageIcon img;

    public Img(int p, int n){
        number = n;
        place = p;
        img = new ImageIcon("u"+number+".jpg", BorderLayout.CENTER);
        setIcon(img);
    }

    public boolean rightPlace(){
        boolean correct=false;
        if(number == place){
            correct = true;
        }
        return correct;
    }
    public void setPlace(int i){
        place = i;
    }
    public int getNumber(){
        return number;
    }
    public int getPlace(){
        return place;
    }
}