获取当前时间（旧版）
Date date = new Date();
String str = String.format("%tY-%tm-%td %tH:%tM:%tS", // 或：%tF %tT
date, date, date, date, date, date); // Y-m-d H:M:s => 2021-07-19 08:33:03
获取当前时间（新版）
LocalDateTime now = LocalDateTime.now();
System.out.println(now.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
LocalDateTime转DateTime
LocalDateTime now = LocalDateTime.now();
Date date = Date.from(Instant.from(now.atZone(ZoneId.systemDefault())));
System.out.printf("%tF %tT\n", date, date);