screen management - Restarting a game

I'm having trouble restarting a 2D game when the user presses the "New Game" button.

Structure of my game:

The game has several 'screens': Opening screen, instructions screen, main game screen, and a game-over screen.

Each screen is an instance of a class: OpeningScreen class, GameScreen class, etc.

There is a class named Main. This class has three roles.

• It's the JFrame (the window) of the program.


• It has the main method - first class to run.


• It has a method that change's screens.

When the program starts, this class runs. When it first runs:

1. Creates a new instance of itself (it's a JFrame-type class).


2. Creates an instance of every 'screen-class'. The constructor of each 'screen-class' takes the instance of Main as an argument: (aka: GameOverScreen gameOverScreen = new GameOver(this)).


3. Creates a new JPanel named mainPanel, and adds it to the JFrame. Any screen to be displayed will be contained in this JPanel (The screens are also JPanel-type classes).

How the changeScreen() method works:

The signature of changeScreen() is this: changeScreen(JPanel from, JPanel to).

Whenever a screen needs to be changed, the current screen that is displayed calls this method, like so: main.changeScreen(this, main.InstructionsScreen). It removes the previous screen from mainPanel and adds the new screen to mainPanel. As said, these screens are created when the program launches.

This is the method that changes screens:

public void changeScreen(JPanel from, JPanel to){


    mainPanel.remove(from);
    mainPanel.add(to);

    mainPanel.revalidate();
    mainPanel.repaint();

}

My problem:

After a game is finished, the Game class calls the changeScreen method: main.changeScreen(this, main.GameOverScreen) .

This replaces the game screen with a game over screen. Pressing the "New Game" button in the game-over screen, calls main.changeScreen(this, main.GameScreen) .

The problem: Pressing the "New Game" button in the game-over screen, indeed displays once again the instance of the Game class. But this is the old instance, so the game is not restarted. It's already finished.

I tried to do the following changes in changeScreen():

public void changeScreen(JPanel from, JPanel to){

    mainPanel.remove(from);

    if(to.equals(gameScreen)){
        gameScreen = null;

        gameScreen = new GameScreen(this);
    }
    mainPanel.add(gameScreen);

    mainPanel.revalidate();
    mainPanel.repaint();

}

This should reset the gameScreen object. But this creates a delay of about 10 seconds when pressing the "New Game" button.

What would be a good way of restarting the game?

Thank you