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 */
    }

}