Date, SimpleDateFormat

package com.main;

import java.text.SimpleDateFormat;
import java.util.Date;

public class Main {
    public static void main(String[] args) throws Exception {
        String dateStr = "2021-03-29 18:29:02";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        Date date = sdf.parse(dateStr);
        System.out.println(date.getTime());
        Date d = new Date(1617028142000l);
        System.out.println(d);
        SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        System.out.println(sdf2.format(d));
        Date now = new Date();
        System.out.println(now);
    }
}