Question

I have a java program which displays an ellipse on the screen and changes its direction through the use of the arrow keys. I constantly call repaint() on the ellipse using a while loop.

The ellipse moves, but the problem is that it leaves a trail of ellipses on its path. How do I make it so that it removes the old ellipses and then repaint the new one?

Code:

public void run(){
        while (animator != null) 
        {
            setBackground(Color.GREEN);
            repaint();
                            // The direction works and the rest works fine.
            player1.move(player1, player1.direction);
            try  
            {  
                Thread.sleep(100);  
            }  
            catch (InterruptedException e)  
            {  
                break;  
            }  
        }
}

// The paintComponent of my player1 is fine.
public void paint(Graphics g){
        Graphics2D g2 = (Graphics2D)g;
        player1.paintComponent(g2, player1);
}

Answer 1

The problem is likely that your paintComponent(Graphics) overriden method is not calling super.paintComponent(g), which clears the canvas, among other things:

// Bad:
@Override
public void paintComponent(Graphics g) {
    // paint the ellipse, etc.
}

// Good:
@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    // paint the ellipse, etc.
}