Very Basic Java Game Code

Here is the working code for a very basic Java game were you move an oval around the screen.
This is to demonstrate the basics of paint(), KeyListener, JFrame and JPanelimport java.awt.Color;import java.awt.Dimension;import java.awt.Graphics;import java.awt.event.KeyEvent;import java.awt.event.KeyListener;import javax.swing.JFrame;import javax.swing.JPanel;public class Main extends JPanel implements KeyListener{private int x = 5, y = 5; private int speed = 5;private Dimension dimension = new Dimension(500,400); public Main(){ setSize(dimension); setPreferredSize(dimension); setFocusable(true); addKeyListener(this); } @Override public void update (Graphics g){ paint(g); } public void paint(Graphics g){ g.setColor(Color.black); g.fillRect(0, 0, getWidth(), getHeight()); g.setColor(Color.white); g.fillOval(x,y,20,20); repaint(); } public static void main (String[] args){ Main game = new Main(); JFrame frame = new JFrame(); frame.setTitle("Game"); frame.add(game); frame.pack(); frame.setResizable(false); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLocationRelativeTo(null); frame.setVisible(true); } @Override public void keyPressed(KeyEvent e) { int c = e.getKeyCode(); if ( c == KeyEvent.VK_W){ y -= speed;} if ( c == KeyEvent.VK_S){ y += speed;} if ( c == KeyEvent.VK_A){ x -= speed;} if ( c == KeyEvent.VK_D){ x += speed;} } @Override public void keyReleased(KeyEvent e) {} @Override public void keyTyped(KeyEvent e) {}}