问答题

本程序中的窗口有一个按钮“得到最新日期”和三个文本框：“年”、“月”和“日”，单击“得到最新日期”按钮后，对应的文本框显示当前的年、月、日信息，如图所示。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Date;
public class exam_25 extends Frame{
public static void main(String args[]){
exam_25 f=new exam_25("exam_7");
Panel pan=new Panel();
f.init();
}
public exam_25(String str){
super(str);
}
public void init(){
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
setSize(200,200);
setLayout(new FlowLayout());
nl=new JLabel("年");
yl=new JLabel("月");
rl=new JLabel("日");
nj=new JTextField(10);
yj=new JTextField(10);
rj=new JTextField(10);
jb=new JButton("得到最新日期");
add(nj);
add(nl);
add(yj);
add(yl);
add(rj);
add(rl);
add(jb);
jb.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
da=______;
nj.setText((new Integer(da.getYear()+1900)).toString());
yj.setText((new Integer(da.getMonth()+1)).toString());
rj.setText((new Integer(______)).toString());
}
});
setVisible(true);
}
private JLabel nl;
private JLabel yl;
private JLabel rl;
private JTextField nj;
private JTextField yj;
private JTextField rj;
private JButton jb;
private Date da;
}