java日期互转：LocalDateTime、String、TimeStamp、Long、Instant、Date

时间：2023-03-10 01:05:15
java日期互转：LocalDateTime、String、TimeStamp、Long、Instant、Date

由于java版本的迭代，一个使用java开发的项目中可能出现多种日期对象，例如LocalDateTime、LocalDate、Date，不像C#只有一个DateTime，因此在各种日期格式或者对象之间的转换显得有点复杂，总是记不住，在需要用到时总是需要依靠搜索引擎，有点浪费时间，所以特意把常用的转换场景总结如下：

1、 LocalDateTime转为String、TimeStamp、Long、Instant、 Date

        System.out.println("----------------LocalDateTime----------------");

        //LocalDateTime -> String

        String localDateTimeToString = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));

        System.out.println("LocalDateTime -> String:  " + localDateTimeToString);

        //LocalDateTime -> TimeStamp

        Timestamp localDateTimeToTimeStamp = Timestamp.valueOf(LocalDateTime.now());

        System.out.println("LocalDateTime -> TimeStamp:  " + localDateTimeToTimeStamp);

        //LocalDateTime -> Long

        Long localDateTimeToLong = Timestamp.valueOf(LocalDateTime.now()).getTime();

        System.out.println("LocalDateTime -> Long:  " + localDateTimeToLong);

        //LocalDateTime -> Instant

        Instant localDateTimeToInstant = LocalDateTime.now().atZone(ZoneId.systemDefault()).toInstant();

        System.out.println("LocalDateTime -> Instant:  " + localDateTimeToInstant);

        //LocalDateTime -> Date

        Date LocalDateTimeToDate = Date.from(LocalDateTime.now().atZone(ZoneId.systemDefault()).toInstant());

        System.out.println("LocalDateTime -> Date:  " + LocalDateTimeToDate);

2、String转为LocalDateTime、 Date

        System.out.println("----------------String----------------");

        //String -> LocalDateTime

        LocalDateTime stringToLocalDateTime =

                LocalDateTime.parse("2018-03-11 15:30:11", DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));

        System.out.println("String -> LocalDateTime:  " + stringToLocalDateTime);

        //String -> Date

        try {

            Date stringToDate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2018-03-11 15:30:11");

            System.out.println("String -> Date:  " + stringToDate);

        } catch (ParseException ex) {

        }

3、Timestamp转为LocalDateTime、 Date

        System.out.println("---------------Timestamp-----------------");

        //Timestamp -> LocalDateTime

        LocalDateTime timeStampToLocalDateTime =

                LocalDateTime.ofInstant(new Timestamp(1520754566856L).toInstant(), ZoneId.systemDefault());

        System.out.println("Timestamp -> LocalDateTime:  " + timeStampToLocalDateTime);

        //Timestamp -> Date

        Date timestampToDate = Date.from(new Timestamp(1520754566856L).toInstant());

        System.out.println("Timestamp -> Date:  " + timestampToDate);

4、Long转为LocalDateTime、 Date

        System.out.println("---------------Long-----------------");

        //Long -> LocalDateTime

        LocalDateTime longToLocalDateTime =

                LocalDateTime.ofInstant(Instant.ofEpochMilli(1520754566856L), ZoneId.systemDefault());

        System.out.println("Long -> LocalDateTime:  " + longToLocalDateTime);

        //Long -> Date

        Date longToDate = new Date(1520754566856L);

        System.out.println("Long -> Date: " + longToDate);

5、Instant转为LocalDateTime、 Date

        System.out.println("----------------Instant----------------");

        //Instant -> LocalDateTime

        LocalDateTime instantToLocalDateTime = LocalDateTime.ofInstant(Instant.now(), ZoneId.systemDefault());

        System.out.println("Instant -> LocalDateTime:  " + instantToLocalDateTime);

        //Instant -> Date

        Date instantToDate = Date.from(Instant.now());

        System.out.println("Instant -> Date:  " + instantToDate);

6、Date转为LocalDateTime、String、TimeStamp、Long、Instant

        System.out.println("----------------Date----------------");

        //Date -> String

        String dateToString = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());

        System.out.println("Date -> String:  " + dateToString);

        //Date -> LocalDateTime

        LocalDateTime dateToLocalDateTime = LocalDateTime.ofInstant(new Date().toInstant(), ZoneId.systemDefault());

        System.out.println("Date -> LocalDateTime:  " + dateToLocalDateTime);

        //Date -> Timestamp

        Timestamp dateToTimestamp = new Timestamp(new Date().getTime());

        System.out.println("Date -> Timestamp:  " + dateToTimestamp);

        //Date -> Long

        Long dateToLong = new Date().getTime();

        System.out.println("Date -> Long: " + dateToLong);

        //Date -> Instant

        Instant dateToInstant = new Date().toInstant();

        System.out.println("Date -> Instant:  " + dateToInstant);

　　

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