Java中SimpleDateFormat方法超详细分析

Date now = new Date();
String formattedDate = sdf.format(now);
System.out.println(formattedDate);

String dateStr = "2022-01-01 12:00:00";
Date parsedDate = sdf.parse(dateStr);
System.out.println(parsedDate);

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class crj {
    public static void main(String[] args) {
        //Date():
        Date d1 = new Date();
        System.out.println(d1);
        //Date(long date):  1000（毫秒）*60*60   一小时
        Date d2 = new Date(1000 * 60 * 60);
        System.out.println(d2);
        Date d = new Date();
//        SimpleDateFormat sdf = new SimpleDateFormat();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
        String s = sdf.format(d);
        System.out.println(s);
        System.out.println("-------");
        //解析
        String ss="2021-10-27 11:11:11";
//        SimpleDateFormat sdf2=new SimpleDateFormat("2021年10月27日 11:11:11");
        SimpleDateFormat sdf2=new SimpleDateFormat("2021-10-27 11:11:11");
        Date dd= null;
        try {
            dd = sdf2.parse(ss);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        System.out.println(dd);
    }
}

import com.itheima_05.DateChooser;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class crj {
    public static void main(String[] args) {
        JFrame jf = new JFrame();
        jf.setTitle("考勤查询");
        jf.setSize(400, 300);
        jf.setDefaultCloseOperation(3);
        jf.setLocationRelativeTo(null);
        jf.setAlwaysOnTop(true);
        jf.setLayout(null);
        //显示考勤日期
        JLabel dataLable = new JLabel("考勤日期");
        dataLable.setBounds(50, 20, 100, 20);
        jf.add(dataLable);
        //开始时间
        JLabel startDateLable = new JLabel("开始时间");
        startDateLable.setBounds(50, 70, 100, 20);
        jf.add(startDateLable);
        DateChooser dateChooser1 = DateChooser.getInstance("yyyy/MM/dd");
        DateChooser dateChooser2 = DateChooser.getInstance("yyyy/MM/dd");
        //开始时间输入框
        JTextField startDateField = new JTextField();
        startDateField.setBounds(50, 100, 100, 20);
        dateChooser1.register(startDateField);
        jf.add(startDateField);
        //结束时间
        JLabel endDateLable = new JLabel("结束时间");
        endDateLable.setBounds(250, 70, 100, 20);
        jf.add(endDateLable);
        //结束时间输入框
        JTextField endDateField = new JTextField();
        endDateField.setBounds(250, 100, 100, 20);
        dateChooser2.register(endDateField);
        jf.add(endDateField);
        //确定按钮
        JButton confirmButton = new JButton("确定");
        confirmButton.setBounds(250, 180, 60, 20);
        jf.add(confirmButton);
        confirmButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd");
                //获取开始 结束时间
                String startDateString = startDateField.getText();
                String endDateString = endDateField.getText();
                try {
                    Date startDate = sdf.parse(startDateString);
                    Date endDate = sdf.parse(endDateString);
                    JOptionPane.showMessageDialog(jf,startDate+"\n"+endDate);
                } catch (ParseException ex) {
                    ex.printStackTrace();
                }
            }
        });
        jf.setVisible(true);
    }
}