Java 8新时间日期库java.time的使用示例

LocalDate today = LocalDate.now(); 
System.out.println("Today's Local date : " + today); 

Output 
Today's Local date : 2020-01-14

LocalDate today = LocalDate.now(); 
int year = today.getYear(); 
int month = today.getMonthValue(); 
int day = today.getDayOfMonth(); 
System.out.printf("Year : %d Month : %d day : %d \t %n", year, month, day); 

Output 
Today's Local date : 2020-01-14 
Year : 2020 Month : 1 day : 14

LocalDate dateOfBirth = LocalDate.of(2010, 01, 14); 
System.out.println("Your Date of birth is : " + dateOfBirth); 

Output : Your Date of birth is : 2010-01-14

LocalDate date1 = LocalDate.of(2020, 01, 14); if(date1.equals(today)){ 
 System.out.printf("Today %s and date1 %s are same date %n", today, date1); 
} 

Output 
today 2020-01-14 and date1 2020-01-14 are same date

LocalDate dateOfBirth = LocalDate.of(2010, 01, 14); 
MonthDay birthday = MonthDay.of(dateOfBirth.getMonth(), dateOfBirth.getDayOfMonth()); 
MonthDay currentMonthDay = MonthDay.from(today); 
if(currentMonthDay.equals(birthday)){ 
 System.out.println("Many Many happy returns of the day !!"); 
}else{ 
 System.out.println("Sorry, today is not your birthday"); 
} 

Output: Many Many happy returns of the day !!

LocalTime time = LocalTime.now(); 
System.out.println("local time now : " + time);

Output 
local time now : 16:33:33.369 // in hour, minutes, seconds, nano seconds

LocalTime time = LocalTime.now(); 
LocalTime newTime = time.plusHours(2); // adding two hours 
System.out.println("Time after 2 hours : " + newTime); 

Output : 
Time after 2 hours : 18:33:33.369

LocalDate nextWeek = today.plus(1, ChronoUnit.WEEKS); 
System.out.println("Today is : " + today); 
System.out.println("Date after 1 week : " + nextWeek); 

Output: 
Today is : 2020-01-14 
Date after 1 week : 2020-01-21

LocalDate previousYear = today.minus(1, ChronoUnit.YEARS); 
System.out.println("Date before 1 year : " + previousYear); 
LocalDate nextYear = today.plus(1, YEARS); 
System.out.println("Date after 1 year : " + nextYear);

Output: 
Date before 1 year : 2019-01-14 
Date after 1 year : 2021-01-14

// Returns the current time based on your system clock and set to UTC. 
Clock clock = Clock.systemUTC(); 
System.out.println("Clock : " + clock);

// Returns time based on system clock zone Clock defaultClock = 
Clock.systemDefaultZone(); 
System.out.println("Clock : " + clock);

Output: 
Clock : SystemClock[Z] 
Clock : SystemClock[Z]
public class MyClass { 
 private Clock clock; // dependency inject ...

 public void process(LocalDate eventDate) {

 if(eventDate.isBefore(LocalDate.now(clock)) { 
  ... 
 } 
 } 
}

LocalDate tomorrow = LocalDate.of(2020, 1, 15);
if(tommorow.isAfter(today)){ 
 System.out.println("Tomorrow comes after today"); 
} 
LocalDate yesterday = today.minus(1, DAYS); 
if(yesterday.isBefore(today)){ 
 System.out.println("Yesterday is day before today"); 
}

Output: 
Tomorrow comes after today 
Yesterday is day before today

// Date and time with timezone in Java 8 ZoneId america = ZoneId.of("America/New_York"); 
LocalDateTime localtDateAndTime = LocalDateTime.now(); 
ZonedDateTime dateAndTimeInNewYork = ZonedDateTime.of(localtDateAndTime, america ); 
System.out.println("Current date and time in a particular timezone : " + dateAndTimeInNewYork);

Output : 
Current date and time in a particular timezone : 2020-01-14T16:33:33.373-05:00[America/New_York]
Exception in thread "main" java.time.zone.ZoneRulesException: Unknown time-zone ID: ASIA/Tokyo
 at java.time.zone.ZoneRulesProvider.getProvider(ZoneRulesProvider.java:272)
 at java.time.zone.ZoneRulesProvider.getRules(ZoneRulesProvider.java:227)
 at java.time.ZoneRegion.ofId(ZoneRegion.java:120)
 at java.time.ZoneId.of(ZoneId.java:403)
 at java.time.ZoneId.of(ZoneId.java:351)

YearMonth currentYearMonth = YearMonth.now(); 
System.out.printf("Days in month year %s: %d%n", currentYearMonth, currentYearMonth.lengthOfMonth()); 
YearMonth creditCardExpiry = YearMonth.of(2018, Month.FEBRUARY); 
System.out.printf("Your credit card expires on %s %n", creditCardExpiry);

Output: 
Days in month year 2020-01: 31 
Your credit card expires on 2018-02

if(today.isLeapYear()){ 
 System.out.println("This year is Leap year"); 
}else { 
 System.out.println("2020 is not a Leap year"); 
}

Output: 2020 is not a Leap year

LocalDate java8Release = LocalDate.of(2020, Month.MARCH, 14); 
Period periodToNextJavaRelease = Period.between(today, java8Release); 
System.out.println("Months left between today and Java 8 release : " + periodToNextJavaRelease.getMonths() );

Output: 
Months left between today and Java 8 release : 2

LocalDateTime datetime = LocalDateTime.of(2020, Month.JANUARY, 14, 19, 30); 
ZoneOffset offset = ZoneOffset.of("+05:30"); 
OffsetDateTime date = OffsetDateTime.of(datetime, offset); 
System.out.println("Date and Time with timezone offset in Java : " + date);

Output : 
Date and Time with timezone offset in Java : 2020-01-14T19:30+05:30

Instant timestamp = Instant.now(); 
System.out.println("What is value of this instant " + timestamp);

Output : 
What is value of this instant 2020-01-14T08:33:33.379Z

String dayAfterTommorrow = "20200116"; 
LocalDate formatted = LocalDate.parse(dayAfterTommorrow, 
DateTimeFormatter.BASIC_ISO_DATE); 
System.out.printf("Date generated from String %s is %s %n", dayAfterTommorrow, formatted);

Output : 
Date generated from String 20200116 is 2020-01-16

String goodFriday = "Apr 18 2020"; 
try { 
 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMM dd yyyy"); 
 LocalDate holiday = LocalDate.parse(goodFriday, formatter); 
 System.out.printf("Successfully parsed String %s, date is %s%n", goodFriday, holiday); 
} catch (DateTimeParseException ex) { 
 System.out.printf("%s is not parsable!%n", goodFriday); 
 ex.printStackTrace(); 
}

Output : 
Successfully parsed String Apr 18 2020, date is 2020-04-18

LocalDateTime arrivalDate = LocalDateTime.now(); 
try { 
 DateTimeFormatter format = DateTimeFormatter.ofPattern("MMM dd yyyy hh:mm a"); 
 String landing = arrivalDate.format(format); 
 System.out.printf("Arriving at : %s %n", landing); 
 } catch (DateTimeException ex) { 
 System.out.printf("%s can't be formatted!%n", arrivalDate); 
 ex.printStackTrace(); 
}

Output : Arriving at : Jan 14 2020 04:33 PM

Instant ins= Instant.now();
System.out.println("10位 秒"+ins.getEpochSecond());
System.out.println("13位 毫秒"+ins.toEpochMilli());