Java8中的LocalDateTime和时间戳timestamp互相转换

将timestamp转为LocalDateTime

public LocalDateTime timestamToDatetime(long timestamp){
        Instant instant = Instant.ofEpochMilli(timestamp);
        return LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
}

将LocalDataTime转为timestamp

public long datatimeToTimestamp(LocalDateTime ldt){
        long timestamp = ldt.toInstant(ZoneOffset.of("+8")).toEpochMilli();
        return timestamp;
}

我在网上还找到了另一个将datetime转为时间戳的方法：

ZoneId zone = ZoneId.systemDefault();
long timestamp = ldt.atZone(zone).toInstant().toEpochMilli();

Java8的时间转为时间戳的大概的思路就是LocalDateTime先转为Instant，设置时区，然后转timestamp。

1.LocalDateTime获取毫秒数

//获取秒数
Long second = LocalDateTime.now().toEpochSecond(ZoneOffset.of("+8"));
//获取毫秒数
Long milliSecond = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli();

2.LocalDateTime与String互转

//时间转字符串格式化
 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
 String dateTime = LocalDateTime.now(ZoneOffset.of("+8")).format(formatter);

//字符串转时间
String dateTimeStr = "2018-07-28 14:11:15";
DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime dateTime = LocalDateTime.parse(dateTimeStr, df);

3.Date与LocalDateTime互转

//将java.util.Date 转换为java8 的java.time.LocalDateTime,默认时区为东8区
    public static LocalDateTime dateConvertToLocalDateTime(Date date) {
        return date.toInstant().atOffset(ZoneOffset.of("+8")).toLocalDateTime();
    }


    //将java8 的 java.time.LocalDateTime 转换为 java.util.Date，默认时区为东8区
    public static Date localDateTimeConvertToDate(LocalDateTime localDateTime) {
        return Date.from(localDateTime.toInstant(ZoneOffset.of("+8")));
    }


    /**
     * 测试转换是否正确
     */
    @Test
    public void testDateConvertToLocalDateTime() {
        Date date = DateUtils.parseDate("2018-08-01 21:22:22", DateUtils.DATE_YMDHMS);
        LocalDateTime localDateTime = DateUtils.dateConvertToLocalDateTime(date);
        Long localDateTimeSecond = localDateTime.toEpochSecond(ZoneOffset.of("+8"));
        Long dateSecond = date.toInstant().atOffset(ZoneOffset.of("+8")).toEpochSecond();
        Assert.assertTrue(dateSecond.equals(localDateTimeSecond));
    }

1.LocalDate转Date

LocalDate nowLocalDate = LocalDate.now();
Date date = Date.from(localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant());

2.LocalDateTime转Date

LocalDateTime localDateTime = LocalDateTime.now();
Date date = Date.from(localDateTime.atZone(ZoneOffset.ofHours(8)).toInstant());

3.Date转LocalDateTime(LocalDate)

Date date = new Date();
LocalDateTime localDateTime = date.toInstant().atZone(ZoneOffset.ofHours(8)).toLocalDateTime();
LocalDate localDate = date.toInstant().atZone(ZoneOffset.ofHours(8)).toLocalDate();

4.LocalDate转时间戳

LocalDate localDate = LocalDate.now();
long timestamp = localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant().toEpochMilli();

5.LocalDateTime转时间戳

LocalDateTime localDateTime = LocalDateTime.now();
long timestamp = localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli();

6.时间戳转LocalDateTime(LocalDate)

long timestamp = System.currentTimeMillis();
LocalDate localDate = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDate();
LocalDateTime localDateTime = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDateTime();

7.计算两天的时间差