Java時間戳、String時間格式和LocalDateTime轉換

1.從默認時區中的系統時鐘獲取當前日期時間

       
   LocalDateTime now = LocalDateTime.now();
   System.out.println(now);//2020-03-16T09:31:18.018

2.LocalDateTime轉時間戳

	LocalDateTime now = LocalDateTime.now();
    long timestamp = now.toInstant(ZoneOffset.of("+8")).toEpochMilli();
    System.out.println(timestamp);//1584321669767  13位的時間戳

3.時間戳轉LocalDateTime

	LocalDateTime now = LocalDateTime.now();
    long timestamp = now.toInstant(ZoneOffset.of("+8")).toEpochMilli();
    LocalDateTime localDateTime = LocalDateTime.ofEpochSecond(timestamp / 1000, 0, ZoneOffset.ofHours(8));
    System.out.println(localDateTime);//2020-03-16T09:31:18

4.String時間轉LocalDateTime

    String time = "2020-03-16 09:27:30";
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    LocalDateTime localDateTime1 = LocalDateTime.parse(time, dateTimeFormatter);
    System.out.println(localDateTime1);//2020-03-16T09:27:30