Javaサンプル(棒グラフをドラッグして値変更)

//Sample06
import java.awt.*;
import java.awt.event.*;
public class Sample06 extends Frame implements MouseListener, MouseMotionListener{
    TextField[] tf=new TextField[2];
    static int x1=303,y1=198,x2=343,y2=198,sw=0;
    //主処理
    public static void main(String ar[]){
        Frame f=new Sample06();
        f.setTitle("棒グラフをドラッグして値変更");
        f.setSize(640,400);
        f.setVisible(true);
    }
    //部品セット
    Sample06(){
        int i;
        setLayout(new FlowLayout());
        for(i=0;i<2;i++){
            tf[i]=new TextField("100",3);
            add(tf[i]);
        }
        addMouseListener(this);
        addMouseMotionListener(this);
        addWindowListener(new WinAdapter());
    }
    //閉じる
    class WinAdapter extends WindowAdapter{
        public void windowClosing(WindowEvent we){System.exit(0);}
    }
    //描画
    public void paint(Graphics g){
        String rs;
        int hei;
        int i;
        int r=2;
        g.clearRect(0,0,639,399);
        for(i=0;i<2;i++){
            rs = tf[i].getText();
            if (rs != null) {
                try {
                    hei=Integer.parseInt(rs);
                    g.setColor(Color.blue);
                    g.fillRect(300+i*40,300-hei,10,hei);
                    g.setColor(Color.red);
                    g.fillOval(305+i*40-r,300-hei-r,2*r,2*r);
                    if (i==0) y1=300-hei-r;
                    if (i==1) y2=300-hei-r;
                } catch (NumberFormatException e) {}
            }
        }
    }
    //マウスイベント
    public void mousePressed(MouseEvent me){
        int x,y;
        sw=0;
        x=me.getX();
        y=me.getY();
        if (Math.abs(x1-x)<3 && Math.abs(y1-y)<3){
            sw=1;
        }
        if (Math.abs(x2-x)<3 && Math.abs(y2-y)<3){
            sw=2;
        }
    }
    //マウスドラッグイベント
    public void mouseDragged(MouseEvent me){
        int y;
        if (sw>0){
            y=me.getY();
            tf[sw-1].setText(""+(298-y));
            repaint();
        }
    }
    public void mouseReleased(MouseEvent me){}
    public void mouseMoved(MouseEvent me){}
    public void mouseEntered(MouseEvent me){}
    public void mouseExited(MouseEvent me){}
    public void mouseClicked(MouseEvent me){}
}