求JAVA程序注释

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;?
public class exam_3{
public static void main(String[] args){
IFrame frame=new IFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);?
frame.show();
}
}

class IFrame extends JFrame{
public static final int DEFAULT_WIDTH=250;?
public static final int DEFAULT_HEIGHT=250;

public IFrame(){
setTitle("Welcome");
setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
IPanel panel=new IPanel();
Container contentPane=getContentPane();?
contentPane.add(panel);?
}
}

class IPanel extends JPanel{
public IPanel(){
setLayout(new FlowLayout(FlowLayout.LEFT));?
JLabel la1=new JLabel("输入整数a:");
JLabel la2=new JLabel("输入整数b:");
final JTextField num1=new JTextField(10);
final JTextField num2=new JTextField(10);
JButton but=ne

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;导入swing包 swing包用于图形用户界面GUI
public class exam_3{
public static void main(String[] args){
IFrame frame=new IFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);关闭应用程序时退出程序
frame.show();
}
}

class IFrame extends JFrame{
public static final int DEFAULT_WIDTH=250;
public static final int DEFAULT_HEIGHT=250;//定义一个属性 且这个属性类型为static final 意思是在整个应用程序中只能赋值一次

public IFrame(){
setTitle("Welcome");
setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
IPanel panel=new IPanel();
Container contentPane=getContentPane(); 获取窗口容器
contentPane.add(panel)；把panel增加到容器中
}
}

class IPanel extends JPanel{
public IPanel(){
setLayout(new FlowLayout(FlowLayout.LEFT));设置布局方式 为流式布局 偏左
JLabel la1=new JLabel("输入整数a:");
JLabel la2=new JLabel("输入整数b:");