java获取当前时间的程序

import javax.swing.*;   //07ppt23-26事件响应

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.*;
import java.util.Calendar;
import java.util.GregorianCalendar;

public class realtime extends JFrame {
  JFrame j=new JFrame();
 JPanel p=new JPanel();
 JButton gett=new JButton("现在时间");
 JLabel h=new JLabel();
 JLabel m=new JLabel();
 JLabel s=new JLabel();
 public realtime(){ 
    j.setSize(800,800);
    j.add(p);
    p.add(h);
    p.add(m);
    p.add(s);
    p.add(gett);
    j.setVisible(true);
    j.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    gett.addActionListener(new gettListener());
    
   }
   public void gtime(){
    Calendar now= new GregorianCalendar();
    int nowh= now.get(Calendar.HOUR_OF_DAY);