目录

Date

SimpleDateFormat

Calendar

LocalDate -- JDK8 后提供日期类(年月日)

LocalTime --  JDK8 后提供时间类(时分秒)

LocalDateTime -- JDK8 后提供日期时间类(年月日时分秒)

Instant -- JDK8 后提供时间戳类

DateTimeFormatter -- JDK8 后提供格式化日期类

Period -- JDK8 后提供日期间隔类

Duration-- JDK8 后提供时间间隔类

ChronoUnit -- JDK8 提供日期时间间隔工具类(推荐)

Date

// 1、创建一个Date类的对象：代表系统此刻日期时间对象Date d = new Date();// 2、获取时间毫秒值long time = d.getTime();// 1、得到当前时间Date d1 = new Date();System.out.println(d1);// 2、当前时间往后走 1小时 121slong time2 = System.currentTimeMillis();time2 += (60 * 60 + 121) * 1000;// 3、把时间毫秒值转换成对应的日期对象。Date d2 = new Date(time2);Date d3 = new Date();d3.setTime(time2);


SimpleDateFormat

// 1、日期对象Date d = new Date();// 2、格式化这个日期对象 (指定最终格式化的形式)SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss EEE a");// 3、开始格式化日期对象成为喜欢的字符串形式String rs = sdf.format(d);// 4、格式化时间毫秒值// 需求：请问121秒后的时间是多少long time1 = System.currentTimeMillis() + 121 * 1000;String rs2 = sdf.format(time1);String dateStr = "2021年08月06日 11:11:11";SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");Date d2 = sdf.parse(dateStr);//往后走2天 14小时 49分 06秒long time = d2.getTime() + (2L*24*60*60 + 14*60*60 + 49*60 + 6) * 1000;//格式化这个时间毫秒值就是结果System.out.println(sdf.format(time));

Calendar

// 1、拿到系统此刻日历对象Calendar cal = Calendar.getInstance();System.out.println(cal); //可以看到所有Calendar的field// 2、获取日历的信息:public int get(int field)：取日期中的某个字段信息。int year = cal.get(Calendar.YEAR);int mm = cal.get(Calendar.MONTH) + 1;int days = cal.get(Calendar.DAY_OF_YEAR) ;// 3、public void set(int field,int value)：修改日历的某个字段信息。cal.set(Calendar.HOUR , 12);// 4.public void add(int field,int amount)：为某个字段增加/减少指定的值// 请问64天后是什么时间cal.add(Calendar.DAY_OF_YEAR , 64);cal.add(Calendar.MINUTE , 59);// 5.public final Date getTime(): 拿到此刻日期对象。Date d = cal.getTime();// 6.public long getTimeInMillis(): 拿到此刻时间毫秒值long time = cal.getTimeInMillis();

LocalDate -- JDK8 后提供日期类(年月日)

// 1、获取本地日期对象。LocalDate nowDate = LocalDate.now();System.out.println("今天的日期：" + nowDate);//今天的日期：int year = nowDate.getYear();System.out.println("year：" + year);int mOnth= nowDate.getMonthValue();System.out.println("month：" + month);int day = nowDate.getDayOfMonth();System.out.println("day：" + day);//当年的第几天int dayOfYear = nowDate.getDayOfYear();//星期System.out.println(nowDate.getDayOfWeek());System.out.println(nowDate.getDayOfWeek().getValue());//月份System.out.println(nowDate.getMonth());//AUGUSTSystem.out.println(nowDate.getMonth().getValue());//8System.out.println("------------------------");LocalDate bt = LocalDate.of(1991, 11, 11);System.out.println(LocalDate.of(1991, Month.NOVEMBER, 11));//相对上面只是把月换成了枚举LocalDate myDate = LocalDate.of(2018, 9, 5);System.out.println("今天是2018-09-06吗？ " + nowDate.equals(myDate));//今天是2018-09-06吗？ falseSystem.out.println(myDate + "是否在" + nowDate + "之前？ " + myDate.isBefore(nowDate));//2018-09-05是否在2018-09-06之前？ trueSystem.out.println(myDate + "是否在" + nowDate + "之后？ " + myDate.isAfter(nowDate));//2018-09-05是否在2018-09-06之后？ false// 判断今天是否是你的生日LocalDate birDate = LocalDate.of(1996, 8, 5);LocalDate nowDate1 = LocalDate.now();MonthDay birMd = MonthDay.of(birDate.getMonthValue(), birDate.getDayOfMonth());MonthDay nowMd = MonthDay.from(nowDate1);System.out.println("今天是你的生日吗？ " + birMd.equals(nowMd));//今天是你的生日吗？ false


LocalTime --  JDK8 后提供时间类(时分秒)

// 1、获取本地时间对象。LocalTime nowTime = LocalTime.now();System.out.println("今天的时间：" + nowTime);//今天的时间：int hour = nowTime.getHour();//时int minute = nowTime.getMinute();//分int secOnd= nowTime.getSecond();//秒int nano = nowTime.getNano();//纳秒System.out.println(nowTime.minusHours(1));//一小时前System.out.println(nowTime.minusMinutes(1));//一分钟前System.out.println(nowTime.minusSeconds(1));//一秒前System.out.println(nowTime.minusNanos(1));//一纳秒前System.out.println(nowTime.plusHours(1));//一小时后System.out.println(nowTime.plusMinutes(1));//一分钟后System.out.println(nowTime.plusSeconds(1));//一秒后System.out.println(nowTime.plusNanos(1));//一纳秒后// 不可变对象，每次修改产生新对象！System.out.println(nowTime);System.out.println("-----");System.out.println(LocalTime.of(8, 20));//时分System.out.println(LocalTime.of(8, 20, 30));//时分秒System.out.println(LocalTime.of(8, 20, 30, 150));//时分秒纳秒LocalTime mTime = LocalTime.of(8, 20, 30, 150);

LocalDateTime -- JDK8 后提供日期时间类(年月日时分秒)

// 日期 时间LocalDateTime nowDateTime = LocalDateTime.now();System.out.println("今天是：" + nowDateTime);//今天是：System.out.println(nowDateTime.getYear());//年System.out.println(nowDateTime.getMonthValue());//月System.out.println(nowDateTime.getDayOfMonth());//日System.out.println(nowDateTime.getHour());//时System.out.println(nowDateTime.getMinute());//分System.out.println(nowDateTime.getSecond());//秒System.out.println(nowDateTime.getNano());//纳秒//日：当年的第几天System.out.println("dayOfYear：" + nowDateTime.getDayOfYear());//dayOfYear：249//星期System.out.println(nowDateTime.getDayOfWeek());//THURSDAYSystem.out.println(nowDateTime.getDayOfWeek().getValue());//4//月份System.out.println(nowDateTime.getMonth());//SEPTEMBERSystem.out.println(nowDateTime.getMonth().getValue());//9LocalDate ld = nowDateTime.toLocalDate();System.out.println(ld);LocalTime lt = nowDateTime.toLocalTime();System.out.println(lt.getHour());System.out.println(lt.getMinute());System.out.println(lt.getSecond());

Instant -- JDK8 后提供时间戳类

// 1、得到一个Instant时间戳对象Instant instant = Instant.now();System.out.println(instant);// 2、系统此刻的时间戳怎么办？Instant instant1 = Instant.now();System.out.println(instant1.atZone(ZoneId.systemDefault()));// 3、如何去返回Date对象Date date = Date.from(instant);System.out.println(date);Instant i2 = date.toInstant();System.out.println(i2);

DateTimeFormatter -- JDK8 后提供格式化日期类

// 本地此刻 日期时间 对象LocalDateTime ldt = LocalDateTime.now();System.out.println(ldt);// 解析/格式化器DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss EEE a");// 正向格式化System.out.println(dtf.format(ldt));// 逆向格式化System.out.println(ldt.format(dtf));// 解析字符串时间DateTimeFormatter dtf1 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");// 解析当前字符串时间成为本地日期时间对象LocalDateTime ldt1 = LocalDateTime.parse("2019-11-11 11:11:11" , dtf1);System.out.println(ldt1);System.out.println(ldt1.getDayOfYear());

Period -- JDK8 后提供日期间隔类

// 当前本地 年月日LocalDate today = LocalDate.now();System.out.println(today);//// 生日的 年月日LocalDate birthDate = LocalDate.of(1998, 10, 13);System.out.println(birthDate);Period period = Period.between(birthDate, today);//第二个参数减第一个参数System.out.println(period.getYears());System.out.println(period.getMonths());System.out.println(period.getDays());

Duration-- JDK8 后提供时间间隔类

// 本地日期时间对象。LocalDateTime today = LocalDateTime.now();System.out.println(today);// 出生的日期时间对象LocalDateTime birthDate = LocalDateTime.of(2021,8,06,01,00,00);System.out.println(birthDate);Duration duration = Duration.between( today , birthDate);//第二个参数减第一个参数System.out.println(duration.toDays());//两个时间差的天数System.out.println(duration.toHours());//两个时间差的小时数System.out.println(duration.toMinutes());//两个时间差的分钟数System.out.println(duration.toMillis());//两个时间差的毫秒数System.out.println(duration.toNanos());//两个时间差的纳秒数

ChronoUnit -- JDK8 提供日期时间间隔工具类(推荐)

// 本地日期时间对象：此刻的LocalDateTime today = LocalDateTime.now();System.out.println(today);// 生日时间LocalDateTime birthDate = LocalDateTime.of(1990,10,1,10,50,59);System.out.println(birthDate);System.out.println("相差的年数：" + ChronoUnit.YEARS.between(birthDate, today));System.out.println("相差的月数：" + ChronoUnit.MONTHS.between(birthDate, today));System.out.println("相差的周数：" + ChronoUnit.WEEKS.between(birthDate, today));System.out.println("相差的天数：" + ChronoUnit.DAYS.between(birthDate, today));System.out.println("相差的时数：" + ChronoUnit.HOURS.between(birthDate, today));System.out.println("相差的分数：" + ChronoUnit.MINUTES.between(birthDate, today));System.out.println("相差的秒数：" + ChronoUnit.SECONDS.between(birthDate, today));System.out.println("相差的毫秒数：" + ChronoUnit.MILLIS.between(birthDate, today));System.out.println("相差的微秒数：" + ChronoUnit.MICROS.between(birthDate, today));System.out.println("相差的纳秒数：" + ChronoUnit.NANOS.between(birthDate, today));System.out.println("相差的半天数：" + ChronoUnit.HALF_DAYS.between(birthDate, today));System.out.println("相差的十年数：" + ChronoUnit.DECADES.between(birthDate, today));System.out.println("相差的世纪（百年）数：" + ChronoUnit.CENTURIES.between(birthDate, today));System.out.println("相差的千年数：" + ChronoUnit.MILLENNIA.between(birthDate, today));System.out.println("相差的纪元数：" + ChronoUnit.ERAS.between(birthDate, today));