悠姿玉茶套盒好用吗:帮我改一下java 程序

import java.awt.* ;
import java.awt.event.* ;
import java.swing.* ;
public class exam{
public static void main (string[] args) {
IFrame frame=new IFrame();
frame.setDefaultCloseOperation (JFrmae,EXIT_ON_CLOSE);
frame.show();
}
}
class IFrame extends JFrame{
public IFrame(){
setTitle("Welcome");
setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
IPanel panel=new IPamel();
Container contentPane=getContentPane();
contentPanel.add(_____);
}
public static final int DEFAULT_WIDTH=250;
public static final int DEFAULT_HEIGHT=120;
}
class IPanel extends JPanel{
public IPanel(){
JLabel prompt=new JLabel("输入你的名字");
final JTextField input=new JTextField(10);
final JLabel output=new JLabel();
JButton btnn=new JButton("确定");
add(prompt);
add(input);
add(btnn);
add(output);
btnn.addActionListener(_____________
{
public void actionPerformed (ActionEvent event)
{
String s=input.getText();
output.setText(s+",欢迎你加入到JAVA学习的行列!");
}
});
}
}