Implementing extended class or not

Question

Another question about inheritance in java: I was wondering about two things: 1) how can I set my program to switch between using an inherited class or not? 2) I'm not sure why my extended class glidingObject.java is not responding to my key presses

Here's my Game.java (which runs the game; I should be passing in some parameter that allows the user to choose which class to use right - either flying object or gliding object? I've also included my two classes for flying object and gliding object)

public class Game extends JPanel {

private static final long serialVersionUID = 1L;

public static int WIDTH = 800, HEIGHT = 750;

public static ArrayList<Rectangle> columns;

public static Random rand;

public static double score;

public static boolean gameOver, started; //two modes, started and gameover

public static String username;

public static String currTime;

public static Timer timer;

public static flyingObject obj;

private PropertyChangeSupport mPcs = new PropertyChangeSupport(this);

public Game(flyingObject object){

    obj = object;
    timer = new Timer(20, new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                tick();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
    });

    columns = new ArrayList<Rectangle>();
    rand = new Random(); 
    Background bk = new Background();

    addColumn(true);
    addColumn(true);
    addColumn(true);
    addColumn(true);

    addMouseListener(new MouseAdapter() {       
        @Override
        public void mouseReleased(MouseEvent e) {
            started = true;
        }
    });

    PropertyChangeListener listener = new PropertyChangeListener() {
        @Override
        public void propertyChange(PropertyChangeEvent evt) {
            try {
                scoreBoard.record();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    };
    this.addPropertyChangeListener(listener);

    getDate(); //get the date of the game played
    mPcs.firePropertyChange("gameOver",false, true); //alert record() method when the game is over
    timer.start();      
}

//adding the column
public static void addColumn(boolean start) {
    int space = 300; 
    int width = 100; 
    int height = 50 + rand.nextInt(300);

    if (start) { 
        //add top and bottom
        columns.add(new Rectangle(WIDTH + width + columns.size() * 300, HEIGHT - height - 120, width, height + 100));
        columns.add(new Rectangle(WIDTH + width + (columns.size() - 1) * 300, 0, width, HEIGHT - height - space));
    }
    else
    {
        columns.add(new Rectangle(columns.get(columns.size() - 1).x + 600, HEIGHT - height - 120, width, height + 100));
        columns.add(new Rectangle(columns.get(columns.size() - 1).x, 0, width, HEIGHT - height - space));
    }
}

//paint the columns
public void paintColumn(Graphics g, Rectangle column) {
    g.setColor(Color.white);
    g.fillRect(column.x, column.y, column.width, column.height);
}

public static void reset() {
    obj = new glidingObject(WIDTH / 2 - 10, HEIGHT / 2 - 10);
    columns.clear();
    score = 0.0;

    addColumn(true);
    addColumn(true);
    addColumn(true);
    addColumn(true);

    gameOver = false;
}

public void tick() throws IOException {
    if (started) {      
        int speed = 10;
        glidingObject.move();
        for (int i = 0; i < columns.size(); i ++) {
            Rectangle column = columns.get(i);
            column.x -= speed;

            if (column.x + column.width < 0) {
                columns.remove(column);
                if  (column.y == 0) {
                    addColumn(false);
                }
            }
        }
        for (Rectangle column: columns) {
            if (column.x == glidingObject.X) {
                score += 0.5;
            }

            if (column.intersects(glidingObject.getBounds())) {
                gameOver = true;

                //when the object crashes, it does not go through the column
                if (glidingObject.X <= column.x) {
                    glidingObject.X = column.x - glidingObject.DIAMETER; 
                }
                else if (glidingObject.Y < column.height) {
                    glidingObject.Y = column.height;
                }      
                Main.gameOver();
            }
        }

        if (glidingObject.Y > HEIGHT || glidingObject.Y < 0) {
            gameOver = true;
            //timer.stop();
            Main.gameOver();
        }

        if (glidingObject.Y + glidingObject.YMotion >= HEIGHT) {
            gameOver = true;
            //timer.stop();
            Main.gameOver();
        }
    }
    //update the display
    repaint();
}

public void getDate() {
    DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
    Date date = new Date();
    currTime = dateFormat.format(date);
    }

 @Override
    public void paintComponent(Graphics g) {

    super.paintComponent(g);


    Background.paint(g);
    glidingObject.paint(g);

    for (Rectangle column: columns) {
        paintColumn(g, column);
    }

    g.setColor(Color.white);
    g.setFont(new Font("Manaspace", 1, 60));

   if (!started) {
       g.drawString("Click to start!", 75, HEIGHT / 2 - 50);
   }

   if (gameOver) {
       g.drawString("Game Over!", 200, HEIGHT / 2 - 50);
   }

   if (!gameOver && started) {
       g.drawString(String.valueOf(score), WIDTH / 2 - 25, 100);
   }
}

}

class flyingobject.java

public class flyingObject implements ActionListener, MouseListener, KeyListener {

static int DIAMETER = 25;
static int Y; // Y position of the unicorn
static int X; // X position of the unicorn
static int YMotion; // Y movement of the unicorn

//parameters are the initial positions
public flyingObject(int xpos, int ypos) {
    X = xpos;
    Y = ypos; // this changes
}

//getters
public int getX() {
    return X;
}

public int getY() {
    return Y;
}

//setters
public void setX(int newX) {
    X = newX;
}

public void setY(int newY) {
    Y = newY;
}

//the bounds of the object (rectangle) 
public static Rectangle getBounds() {
    return new Rectangle(X, Y, DIAMETER, DIAMETER);
}

//the visible component of the object - this can get overriden by subclasses
public static void paint(Graphics g){   
    g.setColor(Color.white);
    g.fillRect(X, Y, DIAMETER, DIAMETER);
}

//the movement component of the object
public static void jump() {     

    if (Game.gameOver) {
        Game.reset();
        Game.gameOver = false;
    }
    if (!Game.started) {
        Game.started = true;
    }
    else if (!Game.gameOver) {
    if (YMotion > 0) {
        YMotion = 0;
    }
    YMotion -= 14;
    }
}

public static void move() {
    if ((Y > 0) && (Y < Game.HEIGHT)) {
        YMotion += 1.5; // gravity
        Y += YMotion;
    }
}

@Override
public void keyTyped(KeyEvent e) {

}

@Override
public void keyPressed(KeyEvent e) {

}

@Override
public void keyReleased(KeyEvent e) {
    if (e.getKeyCode() == KeyEvent.VK_SPACE)
    {
        jump();
    }
}

@Override
public void mouseClicked(MouseEvent e) {
    jump();
}

@Override
public void mousePressed(MouseEvent e) {

}

@Override
public void mouseReleased(MouseEvent e) {

}

@Override
public void mouseEntered(MouseEvent e) {

}

@Override
public void mouseExited(MouseEvent e) {

}

@Override
public void actionPerformed(ActionEvent e) {

}


}

Class glidingobject.java (the game.java should allow the user to choose between just using flying object, or the extended class gliding object)

public class glidingObject extends flyingObject{

//velocity of the object
private static int vx; 
private static int vy;
private static int lives;

public glidingObject(int xpos, int ypos) {
    super(xpos, ypos);
    vx = 0;
    vy = 0; 
    lives = 3;
}

//getter methods

public int getVx() {
    return vx;
}

public int getVy() {
    return vy;
}
//setter methods

public void setVx(int newVx) {
    vx = newVx;
}

public void setVy(int newVy) {
    vy = newVy;
}

//moves the object
public static void jump() {
    X += vx;
    Y += vy;
}

public static void paint(Graphics g) {
    g.setColor(Color.CYAN);
    g.fillOval(X, Y, DIAMETER, DIAMETER);
}

@Override 
public void keyTyped(KeyEvent e) {
    if (e.getKeyCode() == KeyEvent.VK_RIGHT){
        vx = 10;
    }
    if (e.getKeyCode() == KeyEvent.VK_LEFT){
        vx = -10;
    }
    if (e.getKeyCode() == KeyEvent.VK_UP){
        vy = 10;
    }
    if (e.getKeyCode() == KeyEvent.VK_DOWN){
        vy = -10;
    }
}

@Override
public void keyPressed(KeyEvent e) {

}

@Override
public void keyReleased(KeyEvent e) {

}

@Override
public void mouseClicked(MouseEvent e) {

}

@Override
public void mousePressed(MouseEvent e) {

}

@Override
public void mouseReleased(MouseEvent e) {

}

@Override
public void mouseEntered(MouseEvent e) {

}

@Override
public void mouseExited(MouseEvent e) {

}

@Override
public void actionPerformed(ActionEvent e) {

}

}

Answer 1

I should be passing in some parameter that allows the user to choose which class to use right - either flying object or gliding object?

This is where interfaces become so powerful. Both the "flying" and "gliding" objects are going to share some common properties/functionality, these should be described by the interface. You Game should then only accept instances of this interface, it shouldn't care what the implementation, only that they adhere to the agreed interface.

This is principle of "code to interface, not implementation"

How complicated this gets is up to you, for example, you could have abstract implementations which describe "air" based entities and "ground" based entities, from which you could have "powered" and "unpowered" implementations of the abstract "air" class, all of which would be tied back to the "game entity" interface

I'm not sure why my extended class glidingObject.java is not responding to my key presses

This is because you're using KeyListener, this well known for it's focus related issues. See How to Use Key Bindings for the recommended solution