title: JPanel setBackground(Color.BLACK) does nothing
body: <p>I have the folowing custom JPanel and I have aded it to my frame using Netbeans GUI builder but the background won't change! I can see the circle, drawing with g.fillOval(). What's wrong?</p>
  
  <pre><code>public class Board extends JPanel{
  
      private Player player;
  
      public Board(){
          setOpaque(false);
          setBackground(Color.BLACK);  
      }
  
      public void paintComponent(Graphics g){  
          super.paintComponent(g);
          g.setColor(Color.red);
          g.fillOval(player.getxCenter(), player.getyCenter(), player.getRadius(), player.getRadius());
      }
  
      public void updatePlayer(Player player){
          this.player=player;
      }
  }
  </code></pre>