import java.awt.*;
public class Paddle
{
    // instance variables - replace the example below with your own
    private int x, y, length;
    public static final int MAX = 600;
    /**
     * Constructor for objects of class Paddle
     */
    public Paddle(int x, int y, int length)
    {
       this.x = x;
       this.y = y;
       this.length = length;
    }
    public void moveLeft(int n){
        x -= n;
        if (x <0 )
            x=0;
    }
    public void moveRight(int n){
        x += n;
        if (x > MAX )
            x=MAX;
    }
    public void draw(Graphics g){
        g.setColor(Color.BLACK);
        g.fillRect(x, y, length, 20);
    }
}



import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class PaddleTester extends JPanel implements KeyListener
{
    public static int WIDTH=800;
    public static int HEIGHT=600;
    private Font titleFont, regularFont;
    private int keyCode;
    private char c;
    private Paddle paddle;

    public PaddleTester()
    {

        //initialize variables here...
        titleFont = new Font("Roman", Font.BOLD, 18);
        regularFont = new Font("Helvetica", Font.PLAIN, 12);
        keyCode=0;
        c='-';
         paddle = new Paddle(20,300,100);
    }
    public static void main(String[] args) {
        PaddleTester app= new PaddleTester();
        JFrame window = new JFrame("Type a Key to See Its Code");
        window.setSize(WIDTH, HEIGHT);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.getContentPane().add(app);
        window.addKeyListener(app);
        //window.pack();
        window.setVisible(true);

    }
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, getWidth(),getHeight());
        g.setColor(Color.BLUE);
        g.setFont(titleFont);
        g.drawString("Type a Key to See Its Code", 20, 20);
        g.setColor(Color.BLACK);
        g.setFont(regularFont);
        g.drawString("Version 1.0", 20, 40);
        g.drawString("the key char "+c+" has code "+keyCode, 20, 60);
        g.setFont(new Font("Arial", Font.PLAIN, 48));
        g.setColor(Color.red);
        g.drawString("\""+c+"\"",80, 120);
        paddle.draw(g);


    }
    // update is a workaround to cure Windows screen flicker problem
    public void update(Graphics g){
        paint(g);
    }

    // These 3 methods need to be declares to implement the KeyListener Interface
    @Override
    public void keyTyped(KeyEvent e) {}

    @Override
    public void keyPressed(KeyEvent e) 
    {
      keyCode=e.getKeyCode();
      c=e.getKeyChar();
      if (keyCode == 37)
           paddle.moveLeft(3);
      if (keyCode == 39)
           paddle.moveRight(3);
      repaint();
    }

    @Override
    public void keyReleased(KeyEvent e) {}

}