private Color currentColor;
...
public void paint(Graphics g)
{
g.setColor(Color.white);
g.fillRect(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
g.setColor(currrentColor);
g.fillOval(x - radius, y - radius, 2 * radius, 2 * radius);
}
...
public void keyPressed(KeyEvent e)
{
int keyCode = e.getKeyCode();
if (keyCode == KeyEvent.VK_LEFT)
{
x = x - STEP_SIZE;
}
else if (keyCode == KeyEvent.VK_RIGHT)
{
x = x + STEP_SIZE;
}
else if (keyCode == KeyEvent.VK_UP)
{
y = y - STEP_SIZE;
}
else if (keyCode == KeyEvent.VK_DOWN)
{
y = y + STEP_SIZE;
}else currentColor = Color.BLUE;
repaint();
}
You should probably do something like this.