Java时间戳转字符串

String checkin_time = “2021-12-22 08:32:08”
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
long date_temp = Long.valueOf(checkin_time); 
String date_string = simpleDateFormat.format(new Date(date_temp * 1000L));
System.out.println(date_string);