Java – JPanel freezes my entire application when trying to draw

I'm writing the school project of Oregon Trail, and I'm implementing the hunting mini game We are using a model view demonstrator with a card layout When huntingpanel switches to it, run is called and joptionpane appears, but then the whole application freezes and I have to force exit I wrote the whole hunting game in a separate project and just brought the file to the Oregon Trail game It works well with its own JFrame in its own project I don't know what to do

I call this the initialization panel, switch to it, and then run the game

public void initialize(int ammo) {
         player.setBullets(ammo);
         bulletLabel.setText("Bullets: "+player.getBullets());
         presenter.switchToPanel(OregonTrailPresenter.HUNTING_PANEL);
         run();
     }

This is my run method

public void run() {
    // starting message
    JOptionPane.showMessageDialog(null,"You have reached a nearby field to hunt. You will stay\nhere until " +
            "you run out of ammunition or click Return to Trail.");
    // while the player has bullets or doesn't click return to trail
    while (player.getBullets() > 0 && stillHunting) {
        // creates random animals
        checkForAnimal();
        // moves and updates screen
        repaint();
        update();

        try {
            Thread.sleep(50);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    endHunting();
}

The following are other methods used

private void checkForAnimal() {
    int x = 0;
    int y = rand.nextInt(MAX_Y)-40;
    int rand1 = rand.nextInt(100);
    String str = null;
    if (rand1 < 50) {
        str = "left";
        x = MAX_X-40;
    }
    else if (rand1 >= 50) {
        str = "right";
        x = 0;
    }

    double gen = rand.nextGaussian(); // gen is a number from -inf to +inf
    gen = Math.abs(gen); // gen is Now a number from 0 to inf       
    if (gen >= 1.9 && gen < 2.1) { //1.19%
        animalList.add(new Bunny(x,y,str));
    }
    if(gen >= 2.1 && gen < 2.2) {  //0.9%
        animalList.add(new Bear(x,str));
    }
    if (gen >= 2.2 && gen < 2.3) { 
        animalList.add(new Deer(x,str));
    } 

}

    public void update() {
    for (int i = 0; i < animalList.size(); i++) {
        animalList.get(i).move();
    }
}

Solution

You must implement javax swing. Timer instead of thread Sleep (int), because this line of code freezes all GUIs during EDT until thread Sleep (int) ends This is a demonstration if thread. Is passed during EDT Sleep (int) what happens when the GUI is delayed