网上搜索了半天都没有找到Java8的LocalDateTime的工具类，只好自己写了一个，常用功能基本都有。还在用Date的Java同道该换换了。

个人项目地址:https://github.com/KingBoyWorld/common.git，Common模块中有很多实用的工具包，都是优化过的。

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

         */

    }

}

原文地址：https://blog.csdn.net/kingboyworld/article/details/75808108