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1. Date 计算时间差

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;public class DateFormatDemo {public static void main(String[] args) {//设置时间格式，为了 能转换成 字符串DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//当前时间Date beginTime = new Date();//利用时间格式，把当前时间转为字符串String start = df.format(beginTime);//当前时间 转为 长整型 LongLong begin = beginTime.getTime();System.out.println("任务开始，开始时间为："+ start);int num;//循环睡眠 5次，每次 1秒for(int i = 0; i < 5 ; i++){num = i +1;try {//调阻塞(睡眠)方法，这里睡眠 1 秒Thread.sleep(1000);System.out.println(num+"秒");} catch (InterruptedException e) {e.printStackTrace();}}//获取结束时间Date finishTime = new Date();//结束时间 转为 Long 类型Long end = finishTime.getTime();// 时间差 = 结束时间 - 开始时间，这样得到的差值是毫秒级别long timeLag = end - begin;//天long day=timeLag/(24*60*60*1000);//小时long hour=(timeLag/(60*60*1000)-day*24);//分钟long minute=((timeLag/(60*1000))-day*24*60-hour*60);//秒，顺便说一下，1秒 = 1000毫秒long s=(timeLag/1000-day*24*60*60-hour*60*60-minute*60);System.out.println("用了 "+day+"天 "+hour+"时 "+minute+"分 "+s+"秒");System.out.println("任务结束，结束时间为："+ df.format(finishTime));}}

2. 两 LocalDate 计算时间差

2.1 按 整数年 计算 LocalDate

/**
* 传过来的LocalDate类型的日期，距当前时间，相差多少年
* 可计算年龄，工龄等
* 返回Integer类型的数
*/
public static Integer getYear(LocalDate date){//传过来的日期DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy");String dateStr = df.format(date);Long yearLong = Long.parseLong(dateStr);//当前日期LocalDate yearNow = LocalDate.now();String yearNowStr = df.format(yearNow);Long yearNowLong = Long.parseLong(yearNowStr);//当前 - 传过来的参数long age = yearNowLong - yearLong;Integer year = Math.toIntExact(age);return year;
}

2.2 按 年月日 yyyy-MM-dd 判断 俩 LocalDate 大小

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;
import java.util.Date;/*** @author 孙永潮*/
public class DateTimeDemo {public static void main(String[] args) {DateTimeFormatter daf = DateTimeFormatter.ofPattern("yyyy-MM-dd");LocalDate firstDate = LocalDate.of(2023, 3, 22);System.out.println( "firstDate = " + firstDate );LocalDate secondDate = LocalDate.now();System.out.println("secondDate = "  + secondDate);boolean before = firstDate.isBefore(secondDate);System.out.println("判断 firstDate < secondDate 结果为 " +before);boolean after = firstDate.isAfter(secondDate);System.out.println("判断 firstDate > secondDate 结果为 " + after);boolean equal = firstDate.isEqual(secondDate);System.out.println("判断 两日期相等 结果为 " + equal);}
}

3. LocalDateTime 计算时间差

import lombok.extern.slf4j.Slf4j;
import java.time.Duration;
import java.time.LocalDateTime;/*** @author 孙永潮* @date 2022/8/25*/
@Slf4j
public class LocalDateTimeDemo {public static void main(String[] args) {//开始时间LocalDateTime startTime = LocalDateTime.now();int num;//循环睡眠 3次，每次 1秒for(int i = 0; i < 3 ; i++){num = i +1;try {//调阻塞(睡眠)方法，这里睡眠 1 秒Thread.sleep(1000);System.out.println(num+"秒");} catch (InterruptedException e) {e.printStackTrace();}}//结束时间LocalDateTime endTime  = LocalDateTime.now();// 获得两个时间之间的相差值Duration dur= Duration.between(startTime, endTime );//两个时间差的分钟数long minute = dur.toMinutes();//纳秒dur.toNanos();//毫秒long millisecond = dur.toMillis();//秒  ( 1秒 = 1000毫秒 )long s = dur.toMillis()/1000;//分钟dur.toMinutes();//小时dur.toHours();//天数dur.toDays();log.info("用了 {}分", minute);log.info("用了 {}秒", s);log.info("用了 {}毫秒", millisecond);}
}

使用Math.abs让差值永远为正数

import lombok.extern.slf4j.Slf4j;
import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;/*** @author 孙永潮* @date 2022/8/26*/
@Slf4j
public class LocalDateTimeDemo {public static void main(String[] args) {//开始时间LocalDateTime startTime = LocalDateTime.now();int s;//循环睡眠 3次，每次 1秒for(int i = 0; i < 3 ; i++){s = i + 1;try {//调阻塞(睡眠)方法，这里睡眠 1 秒Thread.sleep(1000);System.out.println(s + "秒");} catch (InterruptedException e) {e.printStackTrace();}}//LocalDateTime endTime = LocalDateTime.of(2022, 8, 26, 9, 13, 38);//结束时间LocalDateTime endTime = LocalDateTime.now();//时间格式转换对象DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");String startStr = startTime.format(dtf);System.out.println("开始时间 = "+startStr);String endStr = endTime.format(dtf);System.out.println("结束时间 = " + endStr);//获取开始秒数long startSecond = startTime.toEpochSecond(ZoneOffset.ofHours(0));System.out.println("开始的秒数 = " + startSecond);//获取结束秒数long endSecond = endTime.toEpochSecond(ZoneOffset.ofHours(0));System.out.println("结束的秒数 = " + endSecond);//Math.abs()方法,两个long类型的数相减，得到的永远是正数long abs = Math.abs(endSecond - startSecond);//计算两个时间差的秒数，Java8的API暂时不支持，到Java9开始引入 duration.toSeconds() 支持//获取秒数long second = abs % 60;//获取分钟数long minute = abs / 60 % 60;//获取小时数long hour = abs / 60 / 60 % 24;//获取天数long day = abs / 60 / 60 / 24;System.out.println(day + "天" + hour + "时" + minute + "分" + second + "秒");}}

4. Java获取 当前时间

import cn.hutool.core.date.DateTime;
import cn.hutool.core.text.CharSequenceUtil;
import lombok.extern.slf4j.Slf4j;import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Date;
import java.util.Objects;/*** @author 孙永潮* @date 2023/1/5*/
@Slf4j
public class StringDemo2 {public static void main(String[] args) {Calendar calendar = Calendar.getInstance();// 获取当前年int year = calendar.get(Calendar.YEAR);System.out.println(year + "年");// 获取当前月int month = calendar.get(Calendar.MONTH) + 1;System.out.println(year + "年"+ month + "月");// 获取当前日int day = calendar.get(Calendar.DATE);System.out.println(year + "年"+ month + "月"+ day + "日");// 获取当前小时int hour = calendar.get(Calendar.HOUR_OF_DAY);System.out.println(year + "年"+ month + "月"+ day + "日 "+hour+"点");// 获取当前分钟int minute = calendar.get(Calendar.MINUTE);System.out.println(year + "年"+ month + "月"+ day + "日 "+hour+"点"+minute+"分");// 获取当前秒int second = calendar.get(Calendar.SECOND);System.out.println(year + "年"+ month + "月"+ day + "日 "+hour+"点"+minute+"分"+second+"秒");// 获取当前是本周第几天int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);//星期几String week = dateToWeek(null);System.out.println("按周日为每周的第1天，则现在是本周第" + dayOfWeek + "天 "+week);// 获取当前是本月第几天int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);System.out.println("当前为本 月 第" + dayOfMonth + "天");// 获取当前是本年第几天int dayOfYear = calendar.get(Calendar.DAY_OF_YEAR);System.out.println("当前为本 年 第" + dayOfYear + "天");}//获取星期几public static String dateToWeek(String datetime) {//若参数 为空 或 为空字符串，就把参数 设置为当前时间if (CharSequenceUtil.isBlank(datetime) || Objects.equals(CharSequenceUtil.EMPTY,datetime)){datetime = DateTime.now().toString();}//时间日期转换对象SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd");//星期几的 字符串数组String[] weekDays = {"星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"};//获得一个日历，供计算使用Calendar cal = Calendar.getInstance();Date datet = null;try {datet = f.parse(datetime);cal.setTime(datet);} catch (ParseException e) {e.printStackTrace();}//指示一个星期中的某天。int w = cal.get(Calendar.DAY_OF_WEEK) - 1;if (w < 0){w = 0;}return weekDays[w];}}