Java Zoom In 怎么弄??

小辉仔

用Java 的 language
怎么才能把一个image zoom in & zoom out 呢???
以下是我的 code
到底是那里出了问题导致不能成功??
希望指点指点 哈哈 谢谢

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.net.URL;
public class Q3 extends JApplet implements ActionListener{
    private URL url;
    private ImageIcon img;
    private Image img2;
    private JLabel jlbl1;
    private Object source;
    private Graphics g;
    private JPanel jpBottom = new JPanel(new GridLayout(1,2));
    private JButton jbIn = new JButton ("Zoom In");
    private JButton jbOut = new JButton ("Zoom Out");
    public void init(){
        url=getClass().getResource("image/GreenFrog.gif");
        img = new ImageIcon(url);
        img2 = getImage(url);
        jlbl1 = new JLabel();
        jlbl1.setIcon(img);
        jpBottom.add(jbIn);
        jpBottom.add(jbOut);
        setLayout(new BorderLayout());
        add(jlbl1, BorderLayout.CENTER);
        add(jpBottom, BorderLayout.SOUTH);
      
    }
      public void actionPerformed(ActionEvent e) {
        source = e.getSource();
        showResult();
    }
     public void showResult() {
         if (source == jbIn) {
             g.drawImage(img2,0,0,650,650,this);
         }
         else if(source == jbOut) {
             g.drawImage(img2,0,0,350,350,this);
         }
      }

   }