Programma rotazione poligono

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.*;
import java.awt.geom.*;
import java.awt.Polygon;
public class RotazionePoligonno extends Applet implements MouseListener {
    private int[] xpoints ={0,-10,-7,7,10};
    private int[] ypoints ={-10,-2,10,10,-2};
    private Polygon poly;
  
    int rotation=0;
    public void init(){
         poly=new Polygon(xpoints,ypoints,xpoints.length);
         addMouseListener(this);
        }
       
    public void paint (Graphics g){
    Graphics2D g2D= (Graphics2D) g;
    int ampiezza=getSize().width;
    int altezza=getSize().height;


    g2D.translate(ampiezza/2,altezza/2);
    g2D.scale(20,20);
    g2D.rotate(Math.toRadians(rotation));
    g2D.setColor(Color.RED);
    g2D.draw(poly);
   
    }
    public void mouseEntered (MouseEvent m) {}
    public void mouseExited (MouseEvent m) {}
    public void mouseReleased (MouseEvent m) {}
    public void mouseClicked (MouseEvent m) {}
    public void mousePressed(MouseEvent m) {
        switch (m.getButton() ){
            case MouseEvent.BUTTON1:
            rotation--;
            if (rotation<0)   rotation=359;
            repaint ();
            break;
            case MouseEvent.BUTTON3:
            rotation++;
            if (rotation<360)   rotation=0;
            repaint ();
            break;
        }
    }

     public void keyReleased(KeyEvent k){}
     public void keyTyped(KeyEvent k){}
     public void keyPressed(KeyEvent k){
    
        switch (k.getKeyCode()) {
            case KeyEvent.VK_LEFT:
            rotation--;
            if (rotation<0) rotation=359;
            repaint();
            break;
        case KeyEvent.VK_RIGHT:
        rotation++;
        if (rotation>360) rotation=0;
        repaint();
        break;
      
      }
    }      
}