请各位告诉下这几道JAVA上机题的做法?
2 .请完成下列Java程序：用位于JFrame窗口下方的Open按钮，打开一个文件对话框，检索.gif或者.png图形文件，并在窗口中央将图象显示出来.（提示：将图象文件嵌入图象标内，再将图像图标置于标签中）
注意：请勿改动main主方法和其他已有语句内容，仅在下划线处填入适当的语句.
import java.awt.*;
import jova.awt.event.*;
import java.io.*;
import javax.swing.*;
public class ImageViewer
{ public stratic void main(String[]args)
{ JFrame frame=new ImageViewer Frame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.show();
}
}
class ImgeViewerFrame extends JFrame
{ public ImageViewerFrame()
{ setTitle("ImageViewer");
setSize(DEFAULT_WIDTH,DEFAULT_HEIGTH);
label = new JLAbel();
Container contentpane = getContentpane();
contentpane.add(label.BorderLayout.CENTER);
chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
Button button = new Button("open");
contentpane.add(button,BorderLayout.SOUTH);
button.addActionListener(new
ActionListener()
{ public void actionperformed(ActionEvent evt)
{ int r = chooser.showOpenDialog(null));
if(r = = JFilechooser.APPROVE_OPTLON)
{ String name
=________________
_______________
}
}
});
}
private JLabel label;
private JFileChooser chooser;
private static final int DEFAULT_WIDTH = 300;
private static final int DEFAULT_HEIGHT = 400;
}
3.下面是一个Applet程序，其功能是接收用户输入的两个整数，比较它们的大小，并在用户按下“比较”按钮后，将Applet中显示的“请先输入两个待比较的整数”，改为“两个整数中最大值是：x”，x是两个数中的最大值.请改正程序中的错误（有下划线的语句），使程序能输出正确的结果.
注意：不改动程序的结构，不得增行或删行.
import java.applet.*;
import java.awt.*;
import java.awr.event.*;
public class FindMax extends Applet implements ActionListener{
Label result;
TextField in1,in2;
Button btn;
int a=0,b=0,max;
public void init(){
result = new Label"请先输入两个待比较的整数"};
in1=new TextField(5);
in2=new TextField(5);
btn=new Button("比较")；
add(in1);
add(in2);
add(btn);
add(result);
btn.addActionListener(this);
}
public void actionperformed(ActionEvent e){
a=in1;
n=in2;
if(a>b)
max=a;
else
max=b;
btn.setText("两个数中最大值是:"+max);
}
}
findmax.html:
package ImageViewer;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
public class ImageViewer
{
public static void main(String[] args)
{
JFrame frame=new ImageViewerFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.show();
}
}
class ImageViewerFrame extends JFrame
{
private JLabel label;
private JFileChooser chooser;
private static final int DEFAULT_WIDTH=300;
private static final int DEFAULT_HEIGHT=400;
public ImageViewerFrame()
{
setTitle("ImageViewer");
setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
label=new JLabel();
Container contentPane=getContentPane();
contentPane.add(label,BorderLayout.CENTER);
chooser=new JFileChooser();
chooser.setCurrentDirectory(new File("."));
Button button=new Button("open");
contentPane.add(button,BorderLayout.SOUTH);
button.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent evt)
{
int r=chooser.showOpenDialog(null);
if(r==JFileChooser.APPROVE_OPTION)
{
String name=chooser.getSelectedFile().getPath();
}
}
});
}
}
这个题目有问题！
具体的文件过滤应该这样！
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.swing.*;
public class ImageViewer
{
public static void main(String[] args)
{
JFrame frame=new ImageViewerFrame();
frame.setTitle("ImageViewer");
frame.setSize(300, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.show();
}
}
class ImageViewerFrame extends JFrame
{
public ImageViewerFrame()
{
//set up menu bar
JMenuBar menuBar=new JMenuBar();
setJMenuBar(menuBar);
JMenu menu=new JMenu("File");
menuBar.add(menu);
JMenuItem openItem=new JMenuItem("Open");
menu.add(openItem);
openItem.addActionListener(new FileOpenListener());
JMenuItem exitItem=new JMenuItem("Exit");
menu.add(exitItem);
exitItem.addActionListener(new
ActionListener()
{
public void actionPerformed(ActionEvent event)
{
System.exit(0);
}
}
);
// use a label to display the images
label=new JLabel();
Container contentPane=getContentPane();
contentPane.add(label);
}
private class FileOpenListener implements ActionListener
{
public void actionPerformed(ActionEvent evt)
{
// set up file chooser
JFileChooser chooser=new JFileChooser();
chooser.setCurrentDirectory(new File("."));
// accept all files ending with .gif
chooser.setFileFilter(new javax.swing.filechooser.FileFilter()
{
public boolean accept(File f)
{
return f.getName().toLowerCase().endsWith(".jpg")|| f.isDirectory();
}
public String getDescription()
{
return "*.jpg";
}
});
//show file chooser dialog
int r=chooser.showOpenDialog(ImageViewerFrame.this);
// if image file accepted, set it as icon of the label
if(r==JFileChooser.APPROVE_OPTION)
{
String name=chooser.getSelectedFile().getPath();
label.setIcon(new ImageIcon(name));
}
}
}
private JLabel label;
}
