[hardwired]

Code:

Board board_for_game = new Board(300, 300, car_set_1, exit_1);
RushPanel panel_for_game = new RushPanel(board_for_game);

JFrame f = new JFrame("The Rush Hour Game");
// "panel_for_game" is a reference to this new RushHour
// instance you created with the new operator.
// Since RushHour extends JPanel then this instance
// ("panel_for_game") _is_ a JPanel and can be added to
// your frames contentPane as a component. There is no
// need to make another one. This instance of RushHour
// comes with a paint method override and is ready to go.
//RushPanel rushPanel = new RushPanel(); // create paint panel

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
f.getContentPane().add(panel_for_game);

Code:

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

public class RushPanelRx extends JPanel {
    Board myBoard;

    RushPanelRx(Board board) {
        myBoard = board;
    }

    // Overriding this method is easier for custom drawing.
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        double yInc = (double)(myBoard.getHeight()-1)/Board.NOOFROWS;
        for (int row = 0; row <= Board.NOOFROWS; row ++) {
            int y = (int)(row * yInc);
            g.drawLine(0, y, myBoard.getWidth(), y);
        }
        double xInc = (double)(myBoard.getWidth()-1)/Board.NOOFCOLS;
        for (int col = 0; col <= Board.NOOFROWS; col++) {
            int x = (int)(col * xInc);
            g.drawLine(x, 0, x, myBoard.getHeight());
        }
    }

    public static void main(String[] args) {
        Board board = new Board(300, 300);
        RushPanelRx rushPanel = new RushPanelRx(board);
        JFrame f = new JFrame("The Rush Hour Game");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        f.getContentPane().add(rushPanel);
        f.setSize(350, 350);
        f.setVisible(true);    
    }
}

class Board {
    public static final int NOOFROWS = 6;
    public static final int NOOFCOLS = 6;
    int width;
    int height;

    Board(int width, int height) {
        this.width = width;
        this.height = height;
    }

    public int getWidth() { return width; }

    public int getHeight() { return height; }
}