擷取目前時間
Date類
SimpleDateFormat
Calendar
Date date = new Date();//擷取日期對象//Fri Jan 25 21:42:28 GMT+08:00 2019
String string = date.toLocaleString();//擷取本地時間(過時方法)
System.out.println(string);
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy年MM月dd月");//定義格式化格式
String format2 = simpleDateFormat.format(date);//格式化日期
System.out.println(format2);
Calendar instance = Calendar.getInstance();//擷取月曆對象
Date time3 = instance.getTime();//得到時間對象
System.out.println(time3);
String format3 = simpleDateFormat.format(time3);
System.out.println(format3);
JDK1.8新特性<------>(線程安全)
LocalDate 擷取年月日
LocalTime 擷取時分秒
LocalDateTime 擷取年月日時分秒
package com.westos.csdn;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
public class Demo {
public static void main(String[] args) {
LocalDate now = LocalDate.now();
System.out.println(now);
LocalTime now1 = LocalTime.now();
System.out.println(now1);
LocalDateTime now2 = LocalDateTime.now();
System.out.println(now2);
LocalDate localDate = now2.toLocalDate();
System.out.println(localDate);
LocalTime localTime = now2.toLocalTime();
System.out.println(localTime);
}
}
時間對象的方法
DayOfWeek dayOfWeek = now.getDayOfWeek();//枚舉一周七天
System.out.println(dayOfWeek);
Month month = now.getMonth();//枚舉十二個月份
System.out.println(month);
LocalDate future = LocalDate.of(2020, 1, 1);//設定時間
boolean after = future.isAfter(now);
boolean before = now.isBefore(future);
boolean leapYear = future.isLeapYear();//判斷是否閏年
//将字元串解析成日期對象,進而調用日期中方法
String time = "2019-01-01";
LocalDate parse = LocalDate.parse(time);//預設解析為2019-01-01
System.out.println(parse);
String time1 = "2019年01月01日";
LocalDate parse1 = LocalDate.parse(time1,DateTimeFormatter.ofPattern("yyyy年MM月dd日"));
System.out.println(parse1);
String time2="2019-01-25T20:24:34.378";//這是ISO-8601預設格式,T連接配接
LocalDateTime parse2 = LocalDateTime.parse(time2);
DayOfWeek dayOfWeek1 = parse2.getDayOfWeek();
System.out.println(dayOfWeek1);
//給指定日期加減和設定時間量
//加plusXXX();傳回新的日期對象
LocalDate localDate1 = now.plusDays(1);
LocalDate localDate2 = now.plusYears(2);
//減minusXXX();傳回新的日期對象
LocalDate localDate3 = now.minusMonths(3);
LocalDate localDate4 = now.minusWeeks(3);
//指定時間系列withXXX();
LocalDate localDate5 = now.withYear(2020);
LocalDate localDate6 = now.withDayOfYear(20);
LocalDate with = now.with(TemporalAdjusters.firstDayOfMonth());//傳回這個月的第一天
LocalDate with1 = now.with(TemporalAdjusters.firstInMonth(DayOfWeek.FRIDAY));//擷取這個月第一個在周五
System.out.println(with1);
擷取時間戳Instant和ZoneId時區類
Instant now3 = Instant.now();//擷取時間戳對象,是美國時間.中國時間=(美國時間+8小時)
System.out.println(now3);//2019-01-25T12:44:57.580Z
OffsetDateTime ChinaTime = now3.atOffset(ZoneOffset.ofHours(8));//變成中國時間
System.out.println(ChinaTime);//2019-01-25T20:44:57.580+08:00
//擷取本地時區
ZoneId zoneId = ZoneId.systemDefault();//擷取本地時區
ZonedDateTime ChinaTime1 = now3.atZone(zoneId);//将時間時區化
System.out.println(ChinaTime1);//2019-01-25T20:44:57.580+08:00[GMT+08:00]
| 方法 | 不帶時區的本地時間 | 帶時區的本地時區 |
|---|---|---|
| 年月日 | LocalDate | ZoneDate |
| 時分秒 | LocalTime | ZoneTime |
| 年月日時分秒 | LocalDateTime | ZoneDateTime |
擷取各國時區編号
ZoneId zoneId1 = ZoneId.systemDefault();//擷取本地時區編号
Set<String> availableZoneIds = ZoneId.getAvailableZoneIds();//擷取所有地方的時區編号
for (String availableZoneId : availableZoneIds) {
System.out.println(availableZoneId);
}
案例:
計算兩個時間的間隔,以前是再代碼之前擷取本地時間,再在代碼後擷取本地時間,兩個相減,換算毫秒值.
以前
long start = System.currentTimeMillis();
//代碼
//代碼
//代碼
long end = System.currentTimeMillis();
double second =(end - start) / 1000.0;//擷取秒值
System.out.println(second);
現在用Java提供的方法
Instant start = Instant.now();
for (int i = 0; i < 500000; i++) {
System.out.println(i);
}
Instant end = Instant.now();
Duration between = Duration.between(start, end);
System.out.println(between.getSeconds());//擷取間隔時間的秒值
案例:
計算出生到現在你多少歲了
//出生到現在你多少歲了
LocalDate birth = LocalDate.of(1996, 10, 28);
LocalDate now4 = LocalDate.now();
Period between1 = Period.between(birth, now4);
System.out.println(between1.getYears());
時間矯正器TemporalAdjuster
//擷取下一個的周五
TemporalAdjuster next = TemporalAdjusters.next(DayOfWeek.FRIDAY);
LocalDate with2 = now.with(next);
System.out.println(with2);
案例:
去有的機關辦事,機關人說,你下個工作日再來,請問下個工作日是什麼時候
LocalDate now5 = LocalDate.now();
LocalDate with3 = now.with(new TemporalAdjuster() {
@Override
public Temporal adjustInto(Temporal temporal) {
LocalDate date = (LocalDate) temporal;
DayOfWeek day = date.getDayOfWeek();
//System.out.println(day);
if (day.equals(DayOfWeek.FRIDAY)) {
return now5.plusDays(3);
} else if (day.equals(DayOfWeek.SATURDAY)) {
return now5.plusDays(2);
} else {return now5.plusDays(1);}
}
});
System.out.println(with3);
LocalDate now = LocalDate.now();
LocalDate nextworkdate = now.with(new TemporalAdjuster() {
@Override
public Temporal adjustInto(Temporal temporal) {
LocalDate localDate1 = (LocalDate) temporal;
int day = 0;
while (true) {
LocalDate localDate = localDate1.plusDays(day);
DayOfWeek dayOfWeek = localDate.getDayOfWeek();
if (dayOfWeek.equals(DayOfWeek.FRIDAY) || dayOfWeek.equals(DayOfWeek.SATURDAY)) {
day += 1;
continue;
} else {
day += 1;
break;
}
}
return localDate1.plusDays(day);
}
});
System.out.println(nextworkdate);
格式化日期類
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy年MM月dd月");
LocalDate now6 = LocalDate.now();
String format = now6.format(formatter);//日期類的format方法,傳入格式化對象
System.out.println(format);
String format1 = formatter.format(now6);//格式化類的format方法,傳入日期
System.out.println(format1);
謝謝!
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