程序错误""显示系统当前年月日时分秒 ""该怎么办？

Question

import java.awt.*;import java.awt.event.*;import java.util.Calendar;import javax.swing.*;public class timeTest extends JFrame{final timeTest ti=this;private JLabel label=new JLabel(); public timeTest(){this.setSize(800,400);this.setTitle("时间");this.setLayout(null);this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);Toolkit tk=this.getToolkit();Dimension screenSize=tk.getScreenSize();this.setLocation(screenSize.width/4-this.getWidth()/4, screenSize.height/4-this.getHeight()/4);label.setBounds(200,80,480,80); this.getContentPane().add(label); ActionListener taskPerformer=new ActionListener(){public void actionPerformed(ActionEvent e){Calendar calendar=new Calendar();label.setText(calendar.get(Calendar.YEAR) - 1900 +"年"+calendar.get(Calendar.MONTH)+"月"+calendar.get(Calendar.DAY_OF_WEEK)+"日"+ calendar.get(Calendar.HOUR_OF_DAY) +":"+calendar.get(Calendar.MINUTE)+":"+calendar.get(Calendar.SECOND));label.setFont(new Font("黑体",Font.PLAIN,25));};new Timer(1000, taskPerformer).start(); this.setVisible(true); }public static void main(String[] args) {new timeTest();}}

Answer 1

Date nowDate = nowTime.getTime();
public static String getTime(long time) {
Date da = new Date(time);
String dateFormat = "yyyy-MM-dd HH:mm:ss";
SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
return sdf.format(da);
}

Answer 2

calendar.get(Calendar.YEAR) - 1900 +"年"+
calendar.get(Calendar.MONTH)+"月"+calendar.get(Calendar.DAY_OF_WEEK)
+"日"+ calendar.get(Calendar.HOUR_OF_DAY) +":"+calendar.get(Calendar.MINUTE)
+":"+calendar.get(Calendar.SECOND)) 改成：
SimpleDateFormat sf=new SimpleDateFormat("yyyy年-MM月-dd日 hh时:mm分:ss秒");
String s=sf.format(new Date());

Answer 3

Calendar 不是用来New 的！通过Calendar.getInstance();来创建的！