Java8 日期、時間騷操作
在Java8之前，日期時間API一直被開發者詬病，包括：java.util.Date是可變類型，SimpleDateFormat非線程安全等問題。故此，Java8引入了一套全新的日期時間處理API，新的API基於ISO標準日曆系統。
常用的API類如下：
LocalDate //只包含日期，比如：2018-09-24
LocalTime //只包含時間，比如：10:32:10
LocalDateTime //包含日期和時間，比如：2018-09-24 10:32:10
java.time.format.DateTimeFormatter //時間格式化類
Instant //時間戳
Peroid //時間段
Duration //持續時間、時間差
ZoneOffset //時區偏移量，比如：+8:00
ZonedDateTime //帶時區的日期時間
Clock //時鐘，可用於獲取當前時間戳
LocalDate和LocalTime
從類名就可以看出,LocalDate是表示年月日,而LocalTime是表示時分秒
LocalDate
LocalDate 一般使用場景如下：
LocalDate date = LocalDate.of(2019,6,20);
int year = date.getYear(); //2019
Month month = date.getMonth(); // NOVEMBER
int mon = date.getMonthValue();//6
int dayOfMonth = date.getDayOfMonth(); //20
DayOfWeek dayOfWeek = date.getDayOfWeek(); //SUNDAY
int i = date.lengthOfMonth(); //30
boolean leapYear = date.isLeapYear(); //false
//獲取現在時間
LocalDate now = LocalDate.now(); //2019-06-20
boolean dateEqual = now.equals(LocalDate.of(year,mon,dayOfMonth));//true
除了getxxx方法,還可以使用TemporalField參數給get方法獲取相同的信息(ChronoField是TemporalField的實現)
//獲取現在時間
LocalDate now = LocalDate.now(); //2019-06-20
int year = now.get(ChronoField.YEAR); //2019
int month = now.get(ChronoField.MONTH_OF_YEAR);//6
int dayOfMonth = now.get(ChronoField.DAY_OF_MONTH);//20
int dayOfWeek = now.get(ChronoField.DAY_OF_WEEK);//4
LocalTime
LocalTime now = LocalTime.now();//14:37:26.142
LocalTime time = LocalTime.of(18,18,18);//18:18:18.0
int hour = time.getHour(); //18
int minute = time.getMinute(); //18
int second = time.getSecond(); //18
int nano = time.getNano(); //0
LocalDateTime
LocalDateTime類,結合了上面兩個類,可以同時表示年月日和時分秒
//LocalDateTime基本使用
LocalDateTime localDateTime = LocalDateTime.of(2019,6,20,18,18,18);
//創建LocalDate對象
LocalDate localDate = LocalDate.now();
//調用atTime可以傳入具體時分秒,構成LocalDateTime
LocalDateTime time1 = localDate.atTime(18, 18,18);
//創建LocalTime對象
LocalTime localTime = LocalTime.now();
//調用atDate,傳入具體年月日對象,構成LocalDateTime
LocalDateTime localDateTime1 = localTime.atDate(localDate);
localDateTime.equals(time1); //true
//從LocalDateTime中可以獲取LocalDate和LocalTim
LocalDate date = localDateTime.toLocalDate();
LocalTime time = localDateTime.toLocalTime();
int year = localDateTime.get(ChronoField.YEAR); //localDateTime.getYear() 2019
int month = localDateTime.get(ChronoField.MONTH_OF_YEAR);//localDateTime.getMonthValue() 6
int dayOfMonth = localDateTime.get(ChronoField.DAY_OF_MONTH);//localDateTime.getDayOfMonth() 20
int hour = localDateTime.getHour(); //18
int minute = localDateTime.getMinute(); //18
int second = localDateTime.getSecond(); //18
int nano = localDateTime.getNano(); //0
日期解析與格式化
java.time.format包就是解析日期格式化日期的,最重要的是DateTimeFormatter類,支持以下標記佔位符。
* <pre>
* Symbol Meaning Presentation Examples
* ------ ------- ------------ -------
* G era text AD; Anno Domini; A
* u year year 2004; 04
* y year-of-era year 2004; 04
* D day-of-year number 189
* M/L month-of-year number/text 7; 07; Jul; July; J
* d day-of-month number 10
*
* Q/q quarter-of-year number/text 3; 03; Q3; 3rd quarter
* Y week-based-year year 1996; 96
* w week-of-week-based-year number 27
* W week-of-month number 4
* E day-of-week text Tue; Tuesday; T
* e/c localized day-of-week number/text 2; 02; Tue; Tuesday; T
* F week-of-month number 3
*
* a am-pm-of-day text PM
* h clock-hour-of-am-pm (1-12) number 12
* K hour-of-am-pm (0-11) number 0
* k clock-hour-of-am-pm (1-24) number 0
*
* H hour-of-day (0-23) number 0
* m minute-of-hour number 30
* s second-of-minute number 55
* S fraction-of-second fraction 978
* A milli-of-day number 1234
* n nano-of-second number 987654321
* N nano-of-day number 1234000000
*
* V time-zone ID zone-id America/Los_Angeles; Z; -08:30
* z time-zone name zone-name Pacific Standard Time; PST
* O localized zone-offset offset-O GMT+8; GMT+08:00; UTC-08:00;
* X zone-offset 'Z' for zero offset-X Z; -08; -0830; -08:30; -083015; -08:30:15;
* x zone-offset offset-x +0000; -08; -0830; -08:30; -083015; -08:30:15;
* Z zone-offset offset-Z +0000; -0800; -08:00;
*
* p pad next pad modifier 1
*
* ' escape for text delimiter
* '' single quote literal '
* [ optional section start
* ] optional section end
* # reserved for future use
* { reserved for future use
* } reserved for future use
* </pre>
他有一些預定義常量
LocalDateTime localDateTime = LocalDateTime.of(2019,6,20,18,18,18,999);
String format = localDateTime.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME);//2019-06-20T18:18:18.000000999
String format1 = localDateTime.format(DateTimeFormatter.ISO_DATE_TIME);//2019-06-20T18:18:18.000000999
String format2 = localDateTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss SSSSSSSSS"));//2019-06-20T18:18:18.000000999
LocalDateTime localDateTime1 = LocalDateTime.parse("2019-06-20T18:18:18");
LocalDateTime localDateTime2 = LocalDateTime.parse("2019-06-20 18:18:18",DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
當然也可以創建一個更加複雜的解析器
DateTimeFormatter builder = new DateTimeFormatterBuilder()
.appendText(ChronoField.DAY_OF_MONTH) //首先解析的是一個月的第幾天
.appendLiteral("/") //分隔符
.appendText(ChronoField.MONTH_OF_YEAR) //一年的第幾個月
.appendLiteral(" ") //分隔符
.appendText(ChronoField.YEAR) //年份
.parseCaseInsensitive() //開始解析,不區分大小寫
.toFormatter(Locale.CHINA); //按照哪個國家的方言開始解析
LocalDate date = LocalDate.of(2019, 6, 20);
String format = date.format(builder);// 20/六月 2019
時間調整
Java8提供了新的plusXxx()方法用於計算日期時間增量值，minusXxx()方法用於日期時間的減量值，withXxx()方法指定日期時間指標。
LocalDateTime localDateTime = LocalDateTime.of(2019,6,20,18,18,18);
//2020-03-28 18:06:18
LocalDateTime localDateTime1
= localDateTime.plusYears(1).minusMonths(3).plusDays(8).withHour(18).with(ChronoField.MINUTE_OF_HOUR,6);
TemporalAdjuster
當我們遇到複雜情況的時候,比如調整時間到下個週日之類的要求,我們就需要自定義一個TemporalAdjuster對象,更加靈活的處理日期
java8已經預定義好一些TemporalAdjuster了,可以通過工廠類訪問他們
LocalDateTime localDateTime = LocalDateTime.of(2019,6,20,18,18,18);
LocalDateTime localDateTime2 = localDateTime.with(TemporalAdjusters.nextOrSame(DayOfWeek.SUNDAY));//2019-06-23 18:18:18
LocalDateTime localDateTime3 = localDateTime.with(TemporalAdjusters.lastDayOfMonth());//2019-06-30 18:18:18
定製TemporalAdjuster
創建類實現TemporalAdjuster接口
/**
* 需求:返回下一個工作日,如果日期在週一到週五之間,就返回下一天就好,如果是週五六日就需要返回下週一的日期
*/
public class NextWorkingDay implements TemporalAdjuster {
@Override
public Temporal adjustInto(Temporal temporal) {
//得到參數中是這周的第幾天
int day = temporal.get(ChronoField.DAY_OF_WEEK);
//根據第幾天構造出DayOfWeek枚舉類,容易觀察,當然也可以不用構造
//如果不夠再下面的判斷相等直接改成上面的day就行了
DayOfWeek dayOfWeek = DayOfWeek.of(day);
//需要在參數的基礎上增加幾天
int dayNeedAdd = 1;
//如果是週五,就需要推後三天才是週一
if (dayOfWeek == DayOfWeek.FRIDAY){
dayNeedAdd = 3;
}
//如果是週六,就需要推後兩天才是週一
if (dayOfWeek == DayOfWeek.SATURDAY){
dayNeedAdd = 2;
}
//如果是週日或者當天就是在週一到週五之間的,直接加一就可以,即返回下一天
return temporal.plus(dayNeedAdd, ChronoUnit.DAYS);
}
}
上面說此接口是函數式接口,當然就可以使用Lmabda傳入了,使用如下
LocalDate date = LocalDate.of(2018, 11, 25);//週日
LocalDate nextWorkDay = date.with(new NextWorkingDay()); //2018-11-26
使用lambda
LocalDate date = LocalDate.of(2018, 11, 25);//週日
LocalDate nextWorkDay = date.with(temporal -> {
//具體實現是把上面的實現類NextWorkingDay內實現的方法體貼進來就行了
});
也可以這樣
LocalDate date = LocalDate.of(2018, 11, 25);//週日
TemporalAdjuster nextWorkDay = TemporalAdjusters.ofDateAdjuster(temporal -> {
//具體實現是把上面的實現類NextWorkingDay內實現的方法體貼進來就行了
});
LocalDate date1 = date.with(nextWorkDay);
如上是一個靜態方法,傳入一個UnaryOperator函數式接口的實現即可,就能夠返回一個TemporalAdjuster對象,然後傳入with方法即可