Java8中LocalDateTime与时间戳timestamp的互相转换

Java8 LocalDateTime与timestamp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。

附一个Java8中的LocalDateTime工具类

工具类

package com.kingboy.common.utils.date;

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.time.temporal.TemporalUnit;
import java.util.Date;

/*
 * @author kingboy
 * @Date 2017/7/22 下午2:12
 * @Description LocalDateTimeUtils is used to Java8中的时间类
 */
public class LocalDateTimeUtils {

  //获取当前时间的LocalDateTime对象
  //LocalDateTime.now();

  //根据年月日构建LocalDateTime
  //LocalDateTime.of();

  //比较日期先后
  //LocalDateTime.now().isBefore(),
  //LocalDateTime.now().isAfter(),

  //Date转换为LocalDateTime
  public static LocalDateTime convertDateToLDT(Date date) {
    return LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
  }

  //LocalDateTime转换为Date
  public static Date convertLDTToDate(LocalDateTime time) {
    return Date.from(time.atZone(ZoneId.systemDefault()).toInstant());
  }


  //获取指定日期的毫秒
  public static Long getMilliByTime(LocalDateTime time) {
    return time.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
  }

  //获取指定日期的秒
  public static Long getSecondsByTime(LocalDateTime time) {
    return time.atZone(ZoneId.systemDefault()).toInstant().getEpochSecond();
  }

  //获取指定时间的指定格式
  public static String formatTime(LocalDateTime time,String pattern) {
    return time.format(DateTimeFormatter.ofPattern(pattern));
  }

  //获取当前时间的指定格式
  public static String formatNow(String pattern) {
    return formatTime(LocalDateTime.now(), pattern);
  }

  //日期加上一个数,根据field不同加不同值,field为ChronoUnit.*
  public static LocalDateTime plus(LocalDateTime time, long number, TemporalUnit field) {
    return time.plus(number, field);
  }

  //日期减去一个数,根据field不同减不同值,field参数为ChronoUnit.*
  public static LocalDateTime minu(LocalDateTime time, long number, TemporalUnit field){
    return time.minus(number,field);
  }

  /**
   * 获取两个日期的差 field参数为ChronoUnit.*
   * @param startTime
   * @param endTime
   * @param field 单位(年月日时分秒)
   * @return
   */
  public static long betweenTwoTime(LocalDateTime startTime, LocalDateTime endTime, ChronoUnit field) {
    Period period = Period.between(LocalDate.from(startTime), LocalDate.from(endTime));
    if (field == ChronoUnit.YEARS) return period.getYears();
    if (field == ChronoUnit.MONTHS) return period.getYears() * 12 + period.getMonths();
    return field.between(startTime, endTime);
  }

  //获取一天的开始时间，2017,7,22 00:00
  public static LocalDateTime getDayStart(LocalDateTime time) {
    return time.withHour(0)
        .withMinute(0)
        .withSecond(0)
        .withNano(0);
  }

  //获取一天的结束时间，2017,7,22 23:59:59.999999999
  public static LocalDateTime getDayEnd(LocalDateTime time) {
    return time.withHour(23)
        .withMinute(59)
        .withSecond(59)
        .withNano(999999999);
  }

}

测试类

package com.kingboy.common.localdatetimeutils;

import com.kingboy.common.utils.date.LocalDateTimeUtils;
import org.junit.Test;
import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

import static com.kingboy.common.utils.date.LocalDateTimeUtils.getDayEnd;
import static com.kingboy.common.utils.date.LocalDateTimeUtils.getDayStart;

/**
 * @author kingboy
 * @Date 2017/7/22 下午7:16
 * @Description LocaDateTimeUtilsTest is used to 测试LocalDateTime工具
 */
public class LocaDateTimeUtilsTest {

  @Test
  public void format_test() {
    System.out.println(LocalDateTimeUtils.formatNow("yyyy年MM月dd日 HH:mm:ss"));
  }

  @Test
  public void betweenTwoTime_test() {
    LocalDateTime start = LocalDateTime.of(1993, 10, 13, 11, 11);
    LocalDateTime end = LocalDateTime.of(1994, 11, 13, 13, 13);
    System.out.println("年:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.YEARS));
    System.out.println("月:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.MONTHS));
    System.out.println("日:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.DAYS));
    System.out.println("半日:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.HALF_DAYS));
    System.out.println("小时:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.HOURS));
    System.out.println("分钟:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.MINUTES));
    System.out.println("秒:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.SECONDS));
    System.out.println("毫秒:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.MILLIS));
    //=============================================================================================
    /*
                   年:1
                   月:13
                   日:396
                   半日:792
                   小时:9506
                   分钟:570362
                   秒:34221720
                   毫秒:34221720000
    */
  }

  @Test
  public void plus_test() {
    //增加二十分钟
    System.out.println(LocalDateTimeUtils.formatTime(LocalDateTimeUtils.plus(LocalDateTime.now(),
        20,
        ChronoUnit.MINUTES), "yyyy年MM月dd日 HH:mm"));
    //增加两年
    System.out.println(LocalDateTimeUtils.formatTime(LocalDateTimeUtils.plus(LocalDateTime.now(),
        2,
        ChronoUnit.YEARS), "yyyy年MM月dd日 HH:mm"));
    //=============================================================================================
    /*
                    2017年07月22日 22:53
                    2019年07月22日 22:33
     */
  }

  @Test
  public void dayStart_test() {
    System.out.println(getDayStart(LocalDateTime.now()));
    System.out.println(getDayEnd(LocalDateTime.now()));
    //=============================================================================================
    /*
                    2017-07-22T00:00
                2017-07-22T23:59:59.999999999
     */
  }

}

总结

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