Java8對(duì)日期API做了改進(jìn)，提供了許多好用的方法和接口讯蒲。
首先痊土，最基本也最重要的3個(gè)對(duì)象：
-
LocalDate：日期對(duì)象 -
LocalTime：時(shí)間對(duì)象 -
LocalDateTime：日期時(shí)間對(duì)象，是LocalDate和LocalTime的合集
對(duì)象的創(chuàng)建
以上這3個(gè)對(duì)象爱葵，都各自有3種創(chuàng)建方式施戴。
- 通過
.now()得到當(dāng)前日期時(shí)間對(duì)象。 - 通過
.of()直接指定年月日萌丈，時(shí)分秒赞哗。 -
LocalDate和LocalTime通過解析字符串創(chuàng)建，LocalDateTime可以通過前2個(gè)對(duì)象創(chuàng)建辆雾。
LocalDate對(duì)象3種創(chuàng)建方式以及相關(guān)方法示例
@Test
public void localDate() {
LocalDate date = LocalDate.of(2017, 5, 3);
int year = date.getYear();// 2017
Month month = date.getMonth();// MAY
int day = date.getDayOfMonth();// 3
DayOfWeek dow = date.getDayOfWeek();// Wednesday
int len = date.lengthOfMonth();// 31
boolean leap = date.isLeapYear();// false
System.out.println(year + ", " + month + ", " + day + ", " + dow + ", " + len + ", " + leap);
LocalDate date2 = LocalDate.now();
int year2 = date2.get(ChronoField.YEAR);// 2017
int month2 = date2.get(ChronoField.MONTH_OF_YEAR);// 5
int day2 = date2.get(ChronoField.DAY_OF_MONTH);// 3
int dow2 = date2.get(ChronoField.DAY_OF_WEEK);// 3
System.out.println(year2 + ", " + month2 + ", " + day2 + ", " + dow2);
// 寫2017-3-18會(huì)報(bào)錯(cuò)肪笋，DateTimeParseException異常，可以傳一個(gè)DateTimeFormatter自定義格式
LocalDate date3 = LocalDate.parse("2017-03-18");
int year3 = date3.get(ChronoField.YEAR);
int month3 = date3.get(ChronoField.MONTH_OF_YEAR);
int day3 = date3.get(ChronoField.DAY_OF_MONTH);
int dow3 = date3.get(ChronoField.DAY_OF_WEEK);
System.out.println(year3 + ", " + month3 + ", " + day3 + ", " + dow3);
}
LocalTime對(duì)象3種創(chuàng)建方式以及相關(guān)方法示例
@Test
public void localTime() {
LocalTime time = LocalTime.of(11, 06, 23);
int hour = time.getHour();
int minute = time.getMinute();
int second = time.getSecond();
System.out.println(hour + ":" + minute + ":" + second);
LocalTime time2 = LocalTime.now();
int hour2 = time2.get(ChronoField.HOUR_OF_DAY);
int minute2 = time2.get(ChronoField.MINUTE_OF_HOUR);
int second2 = time2.get(ChronoField.SECOND_OF_MINUTE);
System.out.println(hour2 + ":" + minute2 + ":" + second2);
// 寫13:5:43會(huì)報(bào)錯(cuò)，DateTimeParseException異常藤乙，可以傳一個(gè)DateTimeFormatter自定義格式
LocalTime time3 = LocalTime.parse("13:05:43");
int hour3 = time3.get(ChronoField.HOUR_OF_DAY);
int minute3 = time3.get(ChronoField.MINUTE_OF_HOUR);
int second3 = time3.get(ChronoField.SECOND_OF_MINUTE);
System.out.println(hour3 + ":" + minute3 + ":" + second3);
}
LocalDateTime對(duì)象3種創(chuàng)建方式以及相關(guān)方法示例
@Test
public void localDateTime() {
LocalDate date = LocalDate.now();
LocalTime time = LocalTime.now();
// 創(chuàng)建LocalDateTime
LocalDateTime dateTime = LocalDateTime.of(2017, 5, 3, 11, 53, 23);
LocalDateTime dateTime2 = LocalDateTime.of(date, time);
LocalDateTime dateTime3 = date.atTime(11, 53, 23);
LocalDateTime dateTime4 = date.atTime(time);
LocalDateTime dateTime6 = time.atDate(date);
// 轉(zhuǎn)化
LocalDate date2 = dateTime2.toLocalDate();
LocalTime time2 = dateTime2.toLocalTime();
}
時(shí)間間隔對(duì)象
-
Duration：可以傳2個(gè)localTime對(duì)象猜揪，localDateTime對(duì)象或者Instant對(duì)象 -
Period：用年，月坛梁，日建模而姐，可以傳2個(gè)localDate對(duì)象
@Test
public void between() {
// Duration d1 = Duration.between(time1, time2);
// Duration d2 = Duration.between(dateTime1, dateTime2);
// Duration d3 = Duration.between(instant1, instant2);
Period tenDays = Period.between(LocalDate.of(2014, 3, 8), LocalDate.of(2014, 3, 18));
Duration threeMinutes = Duration.ofMinutes(3);
Duration threeMinutes2 = Duration.of(3, ChronoUnit.MINUTES);
Period tenDays2 = Period.ofDays(10);
Period threeWeeks = Period.ofWeeks(3);
Period twoYearsSixMonthsOneDay = Period.of(2, 6, 1);
}
修改日期時(shí)間對(duì)象
直接使用.with()來修改對(duì)應(yīng)的年月日時(shí)分秒屬性
@Test
public void editDateTime() {
LocalDate date1 = LocalDate.of(2014, 3, 18);// 2014-03-18
LocalDate date2 = date1.withYear(2011);// 2011-03-18
LocalDate date3 = date2.withDayOfMonth(25);// 2011-03-25
LocalDate date4 = date3.with(ChronoField.MONTH_OF_YEAR, 9);// 2011-09-25
}
在現(xiàn)有對(duì)象上做相對(duì)修改
@Test
public void editDateTime() {
LocalDate date1 = LocalDate.of(2014, 3, 18);// 2014-03-18
LocalDate date2 = date1.plusWeeks(1);// 2014-03-25
LocalDate date3 = date2.minusYears(3);// 2011-03-25
LocalDate date4 = date3.plus(6, ChronoUnit.MONTHS);// 2011-09-25
}
自定義修改日期
如果要對(duì)日期做一些復(fù)雜的修改，那么可以通過TemporalAdjusters接口實(shí)現(xiàn)復(fù)雜邏輯划咐。
@Test
public void adjust() {
LocalDate date1 = LocalDate.of(2017, 5, 8);// 2017-05-08
LocalDate date2 = date1.with(TemporalAdjusters.nextOrSame(DayOfWeek.SUNDAY));// 2017-05-14
LocalDate date3 = date2.with(TemporalAdjusters.lastDayOfMonth());// 2017-05-31
}
jdk為我們實(shí)現(xiàn)了一些常用的方法：
- dayOfWeekInMonth：創(chuàng)建一個(gè)新的日期拴念，它的值為同一個(gè)月中每一周的第幾天
- firstDayOfMonth：創(chuàng)建一個(gè)新的日期，它的值為當(dāng)月的第一天
- firstDayOfNextMonth：創(chuàng)建一個(gè)新的日期褐缠，它的值為下月的第一天
- firstDayOfNextYear：創(chuàng)建一個(gè)新的日期政鼠，它的值為明年的第一天
- firstDayOfYear：創(chuàng)建一個(gè)新的日期，它的值為當(dāng)年的第一天
- firstInMonth：創(chuàng)建一個(gè)新的日期队魏，它的值為同一個(gè)月中公般，第一個(gè)符合星期幾要求的值
- lastDayOfMonth：創(chuàng)建一個(gè)新的日期，它的值為當(dāng)月的最后一天
- lastDayOfNextMonth：創(chuàng)建一個(gè)新的日期胡桨，它的值為下月的最后一天
- lastDayOfNextYear：創(chuàng)建一個(gè)新的日期官帘，它的值為明年的最后一天
- lastDayOfYear：創(chuàng)建一個(gè)新的日期，它的值為今年的最后一天
- lastInMonth：創(chuàng)建一個(gè)新的日期昧谊，它的值為同一個(gè)月中遏佣，最后一個(gè)符合星期幾要求的值
- next/previous：創(chuàng)建一個(gè)新的日期，并將其值設(shè)定為日期調(diào)整后或者調(diào)整前揽浙，第一個(gè)符合指定星期幾要求的日期
- nextOrSame/previousOrSame：創(chuàng)建一個(gè)新的日期状婶，并將其值設(shè)定為日期調(diào)整后或者調(diào)整前，第一個(gè)符合指定星期幾要求的日期馅巷，如果該日期已經(jīng)符合要求膛虫，直接返回該對(duì)象
自定義格式化輸出日期
新版本，我們擁有一個(gè)線程安全的類：DateTimeFormatter
來看代碼
@Test
public void formatPrint() {
LocalDate date = LocalDate.of(2014, 3, 18);
String s1 = date.format(DateTimeFormatter.BASIC_ISO_DATE);// 20140318
String s2 = date.format(DateTimeFormatter.ISO_LOCAL_DATE);// 2014-03-18
LocalDate date1 = LocalDate.parse("20140318", DateTimeFormatter.BASIC_ISO_DATE);
LocalDate date2 = LocalDate.parse("2014-03-18", DateTimeFormatter.ISO_LOCAL_DATE);
// 自定義格式
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd/MM/yyyy");
String formattedDate = date.format(formatter);
System.out.println(formattedDate);// 18/03/2014
LocalDate date3 = LocalDate.parse(formattedDate, formatter);
// 帶時(shí)區(qū)的日期(本地化)
DateTimeFormatter italianFormatter = DateTimeFormatter.ofPattern("d. MMMM yyyy", Locale.ITALIAN);
String formattedDate2 = date.format(italianFormatter); // 18. marzo 2014
LocalDate date4 = LocalDate.parse(formattedDate2, italianFormatter);
}
