網上搜索了半天都沒有找到Java8的LocalDateTime的工具類，只好自己寫了一個，常用功能基本都有。還在用Date的Java同道該換換了。

工具類

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中的時間類
 */
 

public class LocalDateTimeUtils {

    //獲取當前時間的LocalDateTime物件
    //LocalDateTime.now();

    //根據年月日構建LocalDateTime
    //LocalDateTime.of();

    //比較日期先後
    //LocalDateTime.now().isBefore(),
    //LocalDateTime.now().isAfter(),

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

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


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

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

    //獲取指定時間的指定格式
    public static String formatTime(LocalDateTime time,String pattern) {
        return time.format(DateTimeFormatter.ofPattern(pattern));
    }

    //獲取當前時間的指定格式
    public static String formatNow(String pattern) {
        return  formatTime(LocalDateTime.now(), pattern);
    }

    //日期加上一個數,根據field不同加不同值,field為ChronoUnit.*
    public static LocalDateTime plus(LocalDateTime time, long number, TemporalUnit field) {
        return time.plus(number, field);
    }

    //日期減去一個數,根據field不同減不同值,field引數為ChronoUnit.*
    public static LocalDateTime minu(LocalDateTime time, long number, TemporalUnit field){
        return time.minus(number,field);
    }

    /**
     * 獲取兩個日期的差  field引數為ChronoUnit.*
     * @param startTime
     * @param endTime
     * @param field  單位(年月日時分秒)
     * @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);
    }

    //獲取一天的開始時間，2017,7,22 00:00
    public static LocalDateTime getDayStart(LocalDateTime time) {
        return time.withHour(0)
                .withMinute(0)
                .withSecond(0)
                .withNano(0);
    }

    //獲取一天的結束時間，2017,7,22 23:59:59.999999999
    public static LocalDateTime getDayEnd(LocalDateTime time) {
        return time.withHour(23)
                .withMinute(59)
                .withSecond(59)
                .withNano(999999999);
    }

}

測試類

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 測試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("小時:" + LocalDateTimeUtils.betweenTwoTime(start, end, ChronoUnit.HOURS));
        System.out.println("分鐘:" + 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
                                      小時:9506
                                      分鐘:570362
                                      秒:34221720
                                      毫秒:34221720000
        */
    }

    @Test
    public void plus_test() {
        //增加二十分鐘
        System.out.println(LocalDateTimeUtils.formatTime(LocalDateTimeUtils.plus(LocalDateTime.now(),
                20,
                ChronoUnit.MINUTES), "yyyy年MM月dd日 HH:mm"));
        //增加兩年
        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
         */
    }

}