package imagetest; 
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class ShowImage extends Applet
{
    private Image img;
    public void init()
    {
       try 
       {
           img=getImage(getDocumentBase(),"0.jpg");
       } catch (Exception ex) 
       {
           ex.printStackTrace();
       } 
    }
    public void paint(Graphics g)
  {

      g.drawImage(img, 0, 0, this);
  }
}

看不懂呀,大哥再教教呀.怎么用都不知道.我想自己选择打开哪张图.

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;

class Demo extends JFrame implements ActionListener
{
    private JButton but = new JButton("打开文件");
    private MyPanel pan = new MyPanel();
    public Demo()
    {
        JPanel pan = new JPanel(new FlowLayout(FlowLayout.CENTER));
        pan.add(but);
        this.getContentPane().add(pan,"North");
        but.addActionListener(this);
        this.getContentPane().add(this.pan);
        this.setSize(800,600);
        this.setLocationRelativeTo(null);
        this.setVisible(true);
    }
    
    public static void main(String[]args)
    {
        new Demo();
    }
    
    public void actionPerformed(ActionEvent e)
    {
        boolean b = false;
        File file = null;
        do
        {
            try
            {
                JFileChooser fc = new JFileChooser();
                fc.showOpenDialog(this);
                file = fc.getSelectedFile();
                if(!file.exists())
                {
                    JOptionPane.showMessageDialog(this,"文件不存在");
                    b = true;
                }
                else
                {
                    b=false;
                    this.pan.setPath(file.getCanonicalPath());
                }
            }
            catch(Exception ex)
            {
                b=false;
            }
        }while(b);
    }
}

class MyPanel extends JPanel
{
    private String path="";

    public void setPath(String path)
    {
       this.path=path;    
    }
    
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        ImageIcon img = new ImageIcon(path);
        int width = img.getIconWidth();
        int height = img.getIconHeight();
        g.drawImage(img.getImage(),(this.getWidth()-width)/2,(this.getHeight()-height)/2,width,height,null);
        this.repaint();
    }
}

我是2楼：
我给出的程序是一个JAVA小应用程序，所以你先配置个HTML文件，代码如下：

<applet code="ShowImage.class" width="600",height="400" codebase="test">
<parm name="font" value="DialogInput" >
</applet>


然后就是正常的编译运行了：(记着把你想显示的图像放在编译后生成的包中哟
并把代码中图片名称做相应修改就行了)

javac -d . ShowImage.java

appletviewer imagetest.html