Java-2D Problem!!

import javax.swing.JFrame;
/**
 * Write a description of class Arena here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Arena extends JFrame
{
   public static void main(String[] args) {
       JFrame arena = new JFrame("Ball_Battle");
       arena.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       arena.setSize(1000, 700);
       arena.setVisible(true);
       arena.setLocationRelativeTo(null);
       arena.add(new Player());
       arena.add(new Enemigo());
   }
}



import java.awt.Graphics2D;
import java.awt.Graphics;
import java.awt.Color;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JPanel;
public class Player extends JPanel
                    implements KeyListener, MouseListener
{
   Line2D.Double disparo;
   Ellipse2D.Double cuerpo;
   
   protected double x = 461;
   protected double dx = 310;
   protected double y = 40;
   protected double dy = y;
   protected boolean vida = true;
   public Player() {
       this.setFocusable(true);
       this.requestFocusInWindow();
       
       cuerpo = new Ellipse2D.Double(x, dx, y, y);
       disparo = new Line2D.Double();
       
       this.addKeyListener(this);
       this.addMouseListener(this);
   }
   
    @Override
   public void paintComponent(Graphics g1) {
       super.paintComponent(g1);
       Graphics2D miC = (Graphics2D) g1;
       miC.setColor(Color.BLUE);
       miC.fill(cuerpo);
       miC.draw(cuerpo);
       Graphics2D miD = (Graphics2D) g1;
       miD.setColor(Color.BLUE);
       miD.fill(disparo);
       miD.draw(disparo);
   }
   
    @Override
   public void keyPressed(KeyEvent e) {
       if(e.getKeyCode() == KeyEvent.VK_LEFT){
           x-=5;
           cuerpo.setFrame(x,dx,y,dy); 
       } 
       
       if(e.getKeyCode() == KeyEvent.VK_RIGHT){
           x+=5;
           cuerpo.setFrame(x,dx,y,dy); 
       }
       
       if(e.getKeyCode() == KeyEvent.VK_UP){
           dx-=5;
           cuerpo.setFrame(x,dx,y,dy); 
       }
       
       if(e.getKeyCode() == KeyEvent.VK_DOWN){
           dx+=5;
           cuerpo.setFrame(x,dx,y,dy); 
       }
       repaint();
   }
   
    @Override
   public void keyReleased(KeyEvent e) {}
   
    @Override
   public void keyTyped(KeyEvent e) {}
   
    @Override 
   public void mouseClicked(MouseEvent e) {
      
   }
  
    @Override
   public void mouseEntered(MouseEvent e) {}

    @Override
   public void mouseExited(MouseEvent e) {}

    @Override
   public void mousePressed(MouseEvent e) {
       disparo.setLine(x+20, dx+20, e.getX(), e.getY());
       repaint();
   }

    @Override
   public void mouseReleased(MouseEvent e) {
       disparo.setLine(x+20, dx+20, x+20, dx+20);
       repaint();
   }
}





import java.util.Random;
import java.awt.Graphics2D;
import java.awt.Graphics;
import java.awt.Color;
import java.awt.geom.Ellipse2D;

public class Enemigo extends Player
{
    Ellipse2D.Double enemy;
    
    private Random random = new Random();
    protected int rX = (int)(random.nextDouble()*943);
    protected int rY = (int)(random.nextDouble()*620);
    protected int rZ = (int)(random.nextDouble()*Math.abs(40-rX));
    
   public Enemigo() {
       generarEnemigo();
   }
    
    @Override
   public void paint(Graphics enemy) {
       super.paint(enemy);
       enemy.setColor(Color.RED);
       enemy.fillOval(rX, rY, 40, 40);
   }
   
   public void generarEnemigo() {
       if(Math.abs(rX-x) < 40 || Math.abs(rY-dx) < 40){
           enemy = new Ellipse2D.Double(rX+(rX/4), rY+(rY/2), 42, 42);
        }
           enemy = new Ellipse2D.Double(rX, rY, 42, 42);
   }
}

super();