JDK8-JODA实战

Java 8日期/时间（ Date/Time）API是开发人员最受追捧的变化之一，Java从一开始就没有对日期时间处理的一致性方法，因此日期/时间API也是除Java核心API以外另一项倍受欢迎的内容。

为什么我们需要新的Java日期/时间API？

在开始研究Java 8日期/时间API之前，让我们先来看一下为什么我们需要这样一个新的API。在Java中，现有的与日期和时间相关的类存在诸多问题，其中有：

1. Java的日期/时间类的定义并不一致，在java.util和java.sql的包中都有日期类，此外用于格式化和解析的类在java.text包中定义。
2. java.util.Date同时包含日期和时间，而java.sql.Date仅包含日期，将其纳入java.sql包并不合理。另外这两个类都有相同的名字，这本身就是一个非常糟糕的设计。
3. 对于时间、时间戳、格式化以及解析，并没有一些明确定义的类。对于格式化和解析的需求，我们有java.text.DateFormat抽象类，但通常情况下，SimpleDateFormat类被用于此类需求。
4. 所有的日期类都是可变的，因此他们都不是线程安全的，这是Java日期类最大的问题之一。
5. 日期类并不提供国际化，没有时区支持，因此Java引入了java.util.Calendar和java.util.TimeZone类，但他们同样存在上述所有的问题。

在现有的日期和日历类中定义的方法还存在一些其他的问题，但以上问题已经很清晰地表明：Java需要一个健壮的日期/时间类。这也是为什么Joda Time在Java日期/时间需求中扮演了高质量替换的重要角色。

// 获取当前时间
LocalDate localDate = LocalDate.now();

System.out.println(localDate);

System.out.println(localDate.getYear() + ", " + localDate.getMonthValue() + ", " + localDate.getDayOfMonth());

System.out.println("------------");

// 生成日期
LocalDate localDate2 = LocalDate.of(2017, 4, 8);
System.out.println(localDate2);

System.out.println("------------");


// 只关注月份和日期
LocalDate localDate3 = LocalDate.of(2010, 3, 25);
MonthDay monthDay = MonthDay.of(localDate3.getMonth(), localDate3.getDayOfMonth());
MonthDay monthDay2 = MonthDay.from(LocalDate.of(2011, 3, 25));

System.out.println(monthDay.equals(monthDay2));

System.out.println("------------");

// 时分秒
LocalTime time = LocalTime.now();
System.out.println(time);

LocalTime time2 = time.plusHours(3).plusMinutes(20);
System.out.println(time2);

System.out.println("------------");

LocalDate localDate1 = localDate.plus(2, ChronoUnit.WEEKS);

System.out.println(localDate1);

System.out.println("------------");

LocalDate localDate4 = localDate.minus(2, ChronoUnit.MONTHS);
System.out.println(localDate4);

System.out.println("------------");
Clock clock = Clock.systemDefaultZone();
System.out.println(clock.millis());

System.out.println("------------");

LocalDate localDate5 = LocalDate.now();
LocalDate localDate6 = LocalDate.of(2017, 4, 25);

System.out.println(localDate5.isAfter(localDate6));
System.out.println(localDate5.isBefore(localDate6));
System.out.println(localDate5.equals(localDate6));

System.out.println("------------");

Set<String> availableZoneIds = ZoneId.getAvailableZoneIds();
System.out.println(availableZoneIds);


System.out.println("------------");

ZoneId zoneId = ZoneId.of("Asia/Shanghai");

LocalDateTime localDateTime = LocalDateTime.now();
System.out.println(localDateTime);

ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime, zoneId);

System.out.println(zonedDateTime);

System.out.println("------------");

YearMonth yearMonth = YearMonth.now();
System.out.println(yearMonth);
System.out.println(yearMonth.lengthOfMonth());
System.out.println(yearMonth.isLeapYear());

System.out.println("------------");

YearMonth yearMonth1 = YearMonth.of(2016, 2);
System.out.println(yearMonth1);
System.out.println(yearMonth1.lengthOfMonth());
System.out.println(yearMonth1.lengthOfYear());
System.out.println(yearMonth1.isLeapYear());

System.out.println("------------");

LocalDate localDate7 = LocalDate.now();
LocalDate localDate8 = LocalDate.of(2017, 3, 25);
Period period = Period.between(localDate7, localDate8);
System.out.println(period.getYears());
System.out.println(period.getMonths());
System.out.println(period.getDays());

System.out.println("------------");

System.out.println(Instant.now());

时间差

// 2014-03-18
LocalDate date = LocalDate.of(2014, 3, 18);
int year = date.getYear();
Month month = date.getMonth();
int day = date.getDayOfMonth();
DayOfWeek dow = date.getDayOfWeek();
int len = date.lengthOfMonth();
// 闰年
boolean leap = date.isLeapYear();
System.out.println(leap);

LocalDate today = LocalDate.now();

// TemporalField方式获取
year = date.get(ChronoField.YEAR);

// 时间
// 13:45:20
LocalTime time = LocalTime.of(13, 45, 20);
int hour = time.getHour();
int minute = time.getMinute();
int second = time.getSecond();


// 从字符串转换
date = LocalDate.parse("2014-03-18");
time = LocalTime.parse("13:45:20");

// LocalDateTime
// 2014-03-18T13:45:20
LocalDateTime dt1 = LocalDateTime.of(2014, Month.MARCH, 18, 13, 45, 20);
LocalDateTime dt2 = LocalDateTime.of(date, time);
LocalDateTime dt3 = date.atTime(13, 45, 20);
LocalDateTime dt4 = date.atTime(time);
LocalDateTime dt5 = time.atDate(date);

// 机器嗦理解的时间类Instant
Instant.ofEpochSecond(0);
// 2秒后加上一千秒
Instant.ofEpochSecond(2, 1_000);
Instant.now().toEpochMilli();

// 所有类都实现了Temporal接口，  Temporal接口定义了如何读取和操纵为时间建模的对象的值

// Duration类主要用于以秒和纳秒恒衡量的时间的长短
Duration d1 = Duration.between(time, time.plusHours(1));
System.out.println(d1.getSeconds());
// Period则以年、月或日的方式对多个时间单位建模
Period tenDays = Period.between(LocalDate.of(2014, 3, 8), LocalDate.of(2014, 3, 18));
System.out.println(tenDays.getDays());
// Duration和Period还有一些工厂类
Duration threeMinutes = Duration.ofMinutes(3);
threeMinutes = Duration.of(3, ChronoUnit.MINUTES);

Period nineDays = Period.ofDays(9);
Period threeWeeks = Period.ofWeeks(3);
Period twoYearsSixMonthsOneDay = Period.of(2, 6, 1);
System.out.println(dt1.plus(twoYearsSixMonthsOneDay));


// 取今天的0点
LocalDateTime localDateTime = LocalDate.now().atTime(0, 0, 0);
long beginOfDay = localDateTime.toEpochSecond(ZoneOffset.of("+08:00"));

System.out.println(localDateTime);
System.out.println(beginOfDay);

计算&格式化

// with是直接修改对应的属性
LocalDate date1 = LocalDate.of(2014, 3, 18);
// 2011-03-18
LocalDate date2 = date1.withYear(2011);
// 2011-03-25
LocalDate date3 = date2.withDayOfMonth(25);
// 2011-09-25
LocalDate date4 = date3.with(ChronoField.MONTH_OF_YEAR, 9);

// plus和minus是相对方式修改属性
// 2014-03-18
date1 = LocalDate.of(2014, 3, 18);
// 2014-03-25
date2 = date1.plusWeeks(1);
// 2011-03-25
date3 = date2.minusYears(3);
// 2011-09-25
date4 = date3.plus(6, ChronoUnit.MONTHS);

// 利用TemporalAdjuster进行复杂处理
date1 = LocalDate.of(2014, 3, 18);
// 下一个星期天 2014-03-23
date2 = date1.with(nextOrSame(DayOfWeek.SUNDAY));
// 这个月最后一天 2014-03-31
date3 = date2.with(lastDayOfMonth());
// 只取工作日
date3 = date2.with(temporal -> {
    DayOfWeek dow = DayOfWeek.of(temporal.get(DAY_OF_WEEK));
    int dayToAdd = 1;
    if (dow == DayOfWeek.FRIDAY) {
        dayToAdd = 3;
    } else if (dow == DayOfWeek.SATURDAY) {
        dayToAdd = 2;
    }
    return temporal.plus(dayToAdd, DAYS);
});

TemporalAdjuster nextWorkingDay = ofDateAdjuster(temporal -> {
    DayOfWeek dow = DayOfWeek.of(temporal.get(DAY_OF_WEEK));
    int dayToAdd = 1;
    if (dow == DayOfWeek.FRIDAY) {
        dayToAdd = 3;
    } else if (dow == DayOfWeek.SATURDAY) {
        dayToAdd = 2;
    }
    return temporal.plus(dayToAdd, DAYS);
});

date2.with(nextWorkingDay);

// 格式化操作

LocalDate date = LocalDate.of(2014, 3, 18);
String s1 = date.format(DateTimeFormatter.BASIC_ISO_DATE);
String s2 = date.format(DateTimeFormatter.ISO_LOCAL_DATE);

date1 = LocalDate.parse("20140318", DateTimeFormatter.BASIC_ISO_DATE);
date2 = LocalDate.parse("2014-03-18", DateTimeFormatter.ISO_LOCAL_DATE);

DateTimeFormatter italianFormatter =
        DateTimeFormatter.ofPattern("d. MMMM yyyy", Locale.ITALIAN);

date1 = LocalDate.of(2014, 3, 18);
// 18. marzo 2014
String formattedDate = date.format(italianFormatter);
date2 = LocalDate.parse(formattedDate, italianFormatter);

italianFormatter = new DateTimeFormatterBuilder().appendText(ChronoField.DAY_OF_MONTH)
        .appendLiteral(". ")
        .appendText(ChronoField.MONTH_OF_YEAR)
        .appendLiteral(" ")
        .appendText(ChronoField.YEAR)
        .parseCaseInsensitive()
        .toFormatter(Locale.ITALIAN);

时区

ZoneId romeZone = ZoneId.of("Europe/Rome");
LocalDate date = LocalDate.of(2014, Month.MARCH, 18);
ZonedDateTime zdt1 = date.atStartOfDay(romeZone);

LocalDateTime dateTime = LocalDateTime.of(2014, Month.MARCH, 18, 13, 45);
ZonedDateTime zdt2 = dateTime.atZone(romeZone);

Instant instant = Instant.now();
ZonedDateTime zdt3 = instant.atZone(romeZone);

//        Instant instantFromDateTime = dateTime.toInstant(romeZone);
LocalDateTime timeFromInstant = LocalDateTime.ofInstant(instant, romeZone);

// 时区偏差
ZoneOffset newYourkOffset = ZoneOffset.of("-05:00");
OffsetDateTime dateTimeInNewYork = OffsetDateTime.of(dateTime, newYourkOffset);

MinguoDate minguoDate = MinguoDate.now();
System.out.println(minguoDate);