如何擦除Graphics对象？

Question

In the code below I am trying to make a ball bounce up and down. The problem is that the ball is painting itself over and over and forming a line rather than a ball moving in a line.

I'm thinking that I need to erase the ball after it draws itself.

 public void paint(Graphics g) {
            if (bouncing) {
                g.setColor(Color.blue);
                g.drawOval(x, y, 10, 10);
                //erase oval here
            }
        }

NOTE: Method paint is being called over and over

Answer 1

Paint the entire background first ...

public void paint(Graphics g)
{
  g.setColor(Color.BLACK);                    // clear the frame ...
  g.fillRect(0, 0, getWidth(), getHeight());

  if (bouncing) 
  {
    g.setColor(Color.blue);
    g.drawOval(x, y, 10, 10);
  }
}