Java 8におけるLocal DateTimeとタイムスタンプの相互変換

Java 8 Local DateTimeとtimestamp変換
timestampをLocal DateTimeに変更します。

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

Local DataTimeをtimestampに変換します。

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

インターネットでもう一つのdatetimeをタイムスタンプに変える方法を見つけました。

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

Java 8の時間がタイムスタンプに変わる大体の考えはLocalDateTimeが先にInstantに変えて、タイムゾーンを設定して、timestampに変えます。
付随するJava 8の中のLocal DateTimeツール類
ツールクラス

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   2:12
 * @Description LocalDateTimeUtils is used to Java8     
 */
public class LocalDateTimeUtils {

  //       LocalDateTime  
  //LocalDateTime.now();

  //       LocalDateTime
  //LocalDateTime.of();

  //      
  //LocalDateTime.now().isBefore(),
  //LocalDateTime.now().isAfter(),

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

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


  //         
  public static Long getMilliByTime(LocalDateTime time) {
    return time.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
  }

  //        
  public static Long getSecondsByTime(LocalDateTime time) {
    return time.atZone(ZoneId.systemDefault()).toInstant().getEpochSecond();
  }

  //           
  public static String formatTime(LocalDateTime time,String pattern) {
    return time.format(DateTimeFormatter.ofPattern(pattern));
  }

  //           
  public static String formatNow(String pattern) {
    return formatTime(LocalDateTime.now(), pattern);
  }

  //       ,  field      ,field ChronoUnit.*
  public static LocalDateTime plus(LocalDateTime time, long number, TemporalUnit field) {
    return time.plus(number, field);
  }

  //       ,  field      ,field   ChronoUnit.*
  public static LocalDateTime minu(LocalDateTime time, long number, TemporalUnit field){
    return time.minus(number,field);
  }

  /**
   *          field   ChronoUnit.*
   * @param startTime
   * @param endTime
   * @param field   (      )
   * @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);
  }

  //         ，2017,7,22 00:00
  public static LocalDateTime getDayStart(LocalDateTime time) {
    return time.withHour(0)
        .withMinute(0)
        .withSecond(0)
        .withNano(0);
  }

  //         ，2017,7,22 23:59:59.999999999
  public static LocalDateTime getDayEnd(LocalDateTime time) {
    return time.withHour(23)
        .withMinute(59)
        .withSecond(59)
        .withNano(999999999);
  }

}

テストクラス

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   7:16
 * @Description LocaDateTimeUtilsTest is used to   LocalDateTime  
 */
public class LocaDateTimeUtilsTest {

  @Test
  public void format_test() {
    System.out.println(LocalDateTimeUtils.formatNow("yyyy MM dd  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(" :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.YEARS));
    System.out.println(" :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.MONTHS));
    System.out.println(" :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.DAYS));
    System.out.println("  :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.HALF_DAYS));
    System.out.println("  :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.HOURS));
    System.out.println("  :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.MINUTES));
    System.out.println(" :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.SECONDS));
    System.out.println("  :" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.MILLIS));
    //=============================================================================================
    /*
                    :1
                    :13
                    :396
                     :792
                     :9506
                     :570362
                    :34221720
                     :34221720000
    */
  }

  @Test
  public void plus_test() {
    //      
    System.out.println(LocalDateTimeUtils.formatTime(LocalDateTimeUtils.plus(LocalDateTime.now(),
        20,
        ChronoUnit.MINUTES), "yyyy MM dd  HH:mm"));
    //    
    System.out.println(LocalDateTimeUtils.formatTime(LocalDateTimeUtils.plus(LocalDateTime.now(),
        2,
        ChronoUnit.YEARS), "yyyy MM dd  HH:mm"));
    //=============================================================================================
    /*
                    2017 07 22  22:53
                    2019 07 22  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
     */
  }

}

締め括りをつける
ここでは、Java 8のLocal DateTimeとタイムスタンプスタンプの切り替えに関する記事を紹介します。これに関連して、Java 8 LocalDateTimeとtimestampの変換内容は以前の文章を検索したり、以下の関連記事を見たりしてください。これからもよろしくお願いします。