JDK1.8时间工具类

JDK1.8时间工具类

一、特点：比起Date类和Calendar类，jdk1.8的时间类更全面、线程安全、可修改

二、JDK1.8各时间类特点及应用

2.1、LocalDate类

 //取当前日期
LocalDate today=LocalDate.now();
System.out.println("today = " + today);

输出：today = 2020-11-24

 //取当前日期
 LocalDate today=LocalDate.now();
 //获取当前是一周的第几天
 int dayOfWeek = today.getDayOfWeek().getValue();
 System.out.println("dayOfWeek = " + dayOfWeek);
 //获取当前日
 int dayOfMonth = today.getDayOfMonth();
 System.out.println("dayOfMonth = " + dayOfMonth);
 //获取当前是一年中的第几天
 int dayOfYear = today.getDayOfYear();
 System.out.println("dayOfYear = " + dayOfYear);
 //获取当前月
 int monthValue = today.getMonthValue();
 System.out.println("monthValue = " + monthValue);
 //获取当前年
 int year = today.getYear();
 System.out.println("year = " + year);

输出：
dayOfWeek = 2
dayOfMonth = 24
dayOfYear = 329
monthValue = 11
year = 2020

 //根据年月日取日期,12月就是12月，月份不需要像date和calendar类0-11
 LocalDate myDate = LocalDate.of(2020, 11, 11);
 System.out.println("myDate = " + myDate);

输出：myDate = 2020-11-11

 //根据字符串取1：（必须严格按照格式:yyyy-MM-dd）
LocalDate parseStr1 = LocalDate.parse("2020-11-24");
System.out.println("parseStr1 = " + parseStr1);

输出：parseStr1 = 2020-11-24

 //根据字符串取2：（自定义格式）
LocalDate parseStr2 = LocalDate.parse("2020/08/02", DateTimeFormatter.ofPattern("yyyy/MM/dd"));
System.out.println("parseStr2 = " + parseStr2);

输出：parseStr2 = 2020-08-02

//取本月第一天
LocalDate firstDayOfMonth = today.with(TemporalAdjusters.firstDayOfMonth());
System.out.println("firstDayOfMonth = " + firstDayOfMonth);

输出：firstDayOfMonth = 2020-11-01

//取本月第2天：
LocalDate secondDayOfMonth = today.withDayOfMonth(2);
System.out.println("secondDayOfMonth = " + secondDayOfMonth);

输出：secondDayOfMonth = 2020-11-02

//取本月最后一天
LocalDate lastDayOfMonth = today.with(TemporalAdjusters.lastDayOfMonth());
System.out.println("lastDayOfMonth = " + lastDayOfMonth);

输出：lastDayOfMonth = 2020-11-30

 //取下一天
LocalDate tomorrow = lastDayOfMonth.plusDays(1);
System.out.println("tomorrow = " + tomorrow);

输出：tomorrow = 2020-12-01

 //取2020年11月第一个周一
LocalDate firstMondayOf2020 = LocalDate.parse("2020-11-01").with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
System.out.println("firstMondayOf2020 = " + firstMondayOf2020);

输出：firstMondayOf2020 = 2020-11-02

//几个使用方法
LocalDate today = LocalDate.now();

//判断 today 是否为闰年
boolean isLeapYear = today.isLeapYear();
System.out.println("isLeapYear = " + isLeapYear);

//获取 today 是该年的第几季度
int quarterOfYear = today.get(IsoFields.QUARTER_OF_YEAR);
System.out.println("quarterOfYear = " + quarterOfYear);

//获取 today 是该季度的第几天
int daysOfQuarter = today.get(IsoFields.DAY_OF_QUARTER);
System.out.println("daysOfQuarter = " + daysOfQuarter);

输出：
isLeapYear = true
quarterOfYear = 4
daysOfQuarter = 55

2.2、LocalTime类

//获取当前时间(带有毫秒)
LocalTime timeMills = LocalTime.now();
System.out.println("timeMills = " + timeMills);
//在timeMills的基础上获取不带毫秒的time
//nanoSecond纳秒,十亿分之一秒
LocalTime time1 = timeMills.withNano(0);
System.out.println("time1 = " + time1);

//设置并得到时间对象
LocalTime time2 = LocalTime.of(12, 00, 00);
System.out.println("time2 = " + time2);

//解析时间字符串
LocalTime parseStr1 = LocalTime.parse("12:30:00");
System.out.println("parseStr1 = " + parseStr1);
LocalTime parseStr2 = LocalTime.parse("12时30分00秒", DateTimeFormatter.ofPattern("HH时mm分ss秒"));
System.out.println("parseStr2 = " + parseStr2);

//获取一天的第多少秒的时间对象
LocalTime time3 = LocalTime.ofSecondOfDay(18 * 60 * 60 + 60 * 30);
System.out.println("time3 = " + time3);

//MIN、MAX、 NOON、 MIDNIGHT
//MIN和MIDNIGHT都是00:00，意味一天的开始
//NOON是中午12:00，意味着半天
//MAX是23:59:59.999999999，意味着一天的结束
System.out.println("MIN = " + LocalTime.MIN);
System.out.println("MIDNIGHT = " + LocalTime.MIDNIGHT);
System.out.println("NOON = " + LocalTime.NOON);
System.out.println("MAX = " + LocalTime.MAX);

输出：
timeMills = 22:58:55.326
time1 = 22:58:55
time2 = 12:00
parseStr1 = 12:30
parseStr2 = 12:30
time3 = 18:30
MIN = 00:00
MIDNIGHT = 00:00
NOON = 12:00
MAX = 23:59:59.999999999

//获取当前时间(带有毫秒)
LocalTime timeMills = LocalTime.now();
System.out.println("timeMills = " + timeMills);
//在timeMills的基础上获取不带毫秒的time
//nanoSecond纳秒,十亿分之一秒
LocalTime time = timeMills.withNano(0);
System.out.println("time = " + time);

//获取时
int hour = time.getHour();
System.out.println("hour = " + hour);
//获取分
int minute = time.getMinute();
System.out.println("minute = " + minute);
//获取秒
int second = time.getSecond();
System.out.println("second = " + second);

//下班时间
LocalTime workOver = LocalTime.of(18, 30, 00);

//睡觉时间
LocalTime sleepTime = LocalTime.of(23, 30, 00);

//判断现在是否是下班时间
boolean after = time.isAfter(workOver);
System.out.println("after = " + after);
//判断现在是否是睡觉时间
boolean before = time.isBefore(sleepTime);
System.out.println("before = " + before);

//现在和下班时间比较
int i = time.compareTo(workOver);
System.out.println("i = " + i);
//现在和睡觉时间比较
int j = time.compareTo(sleepTime);
System.out.println("j = " + j);

//获取离现在1个半小时的时间
LocalTime time2 = time.plusHours(1).plusMinutes(30);
System.out.println("time2 = " + time2);

输出：
timeMills = 23:11:22.379
time = 23:11:22
hour = 23
minute = 11
second = 22
after = true
before = true
i = 1
j = -1
time2 = 00:41:22