Java 8 Date/Time API

지금까지의 Date/Time 관련 API는 개발자에게 외면을 받아왔지만, Java 8에서는 "JSR 310: Data and Time API" Spec을 구현하여 획기적으로 변화했다고 한다. 새로운 Date/Time 클래스는 java.time.* 으로 패키징 되어 있다.

System의 Locale에 따른 날짜 및 시간 형식으로 표현된다. 불변성을 가지고 Thread Safe 하다.

java.time.LocalDate

package org.smarttechie; import java.time.LocalDate; import java.time.temporal.ChronoUnit; /** * This class demonstrates JAVA 8 data and time API * * @author Siva Prasad Rao Janapati * */ public class LocalDateDemonstration { /** * @param args */ public static void main(String[] args) { // Create date LocalDate localDate = LocalDate.now(); System.out.println("The local date is :: " + localDate); // Find the length of the month. That is, how many days are there for // this month. System.out.println("The number of days available for this month:: " + localDate.lengthOfMonth()); // Know the month name System.out.println("What is the month name? :: " + localDate.getMonth().name()); // add 2 days to the today's date. System.out.println(localDate.plus(2, ChronoUnit.DAYS)); // substract 2 days from today System.out.println(localDate.minus(2, ChronoUnit.DAYS)); // Convert the string to date System.out.println(LocalDate.parse("2017-04-07")); } } ---------------------------------- The local date is :: 2016-04-28 The number of days available for this month:: 30 What is the month name? :: APRIL 2016-04-30 2016-04-26 2017-04-07

java.time.LocalTime

package org.smarttechie; import java.time.LocalTime; import java.time.temporal.ChronoUnit; /** * This class demonstrates JAVA 8 data and time API * * @author Siva Prasad Rao Janapati * */ public class LocalTimeDemonstration { /** * @param args */ public static void main(String[] args) { // Get local time LocalTime localTime = LocalTime.now(); System.out.println(localTime); // Get the hour of the day System.out.println("The hour of the day:: " + localTime.getHour()); // add 2 hours to the time. System.out.println(localTime.plus(2, ChronoUnit.HOURS)); // add 6 minutes to the time. System.out.println(localTime.plusMinutes(6)); // substract 2 hours from current time System.out.println(localTime.minus(2, ChronoUnit.HOURS)); } } -------------------------------------- 13:33:53.602 The hour of the day:: 13 15:33:53.602 13:39:53.602 11:33:53.602

java.time.LocalDateTime

package org.smarttechie; import java.time.LocalDateTime; import java.time.temporal.ChronoUnit; /** * This class demonstrates JAVA 8 data and time API * * @author Siva Prasad Rao Janapati * */ public class LocalDateTimeDemonstration { /** * @param args */ public static void main(String[] args) { // Get LocalDateTime object LocalDateTime localDateTime = LocalDateTime.now(); System.out.println(localDateTime); // Find the length of month. That is, how many days are there for this // month. System.out.println("The number of days available for this month:: " + localDateTime.getMonth().length(true)); // Know the month name System.out.println("What is the month name? :: " + localDateTime.getMonth().name()); // add 2 days to today's date. System.out.println(localDateTime.plus(2, ChronoUnit.DAYS)); // substract 2 days from today System.out.println(localDateTime.minus(2, ChronoUnit.DAYS)); } } ------------------------------------ 2016-04-28T13:34:58.061 The number of days available for this month:: 30 What is the month name? :: APRIL 2016-04-30T13:34:58.061 2016-04-26T13:34:58.061

java.time.Period

기간을 Day보다 적은 단위로 표현이 가능하다. 시, 분, 초, 밀리, 나노

package org.smarttechie; import java.time.LocalDate; import java.time.Period; import java.time.temporal.ChronoUnit; /** * This class demonstrates JAVA 8 data and time API * * @author Siva Prasad Rao Janapati * */ public class PeriodDemonstration { /** * @param args */ public static void main(String[] args) { LocalDate localDate = LocalDate.now(); Period period = Period.between(localDate, localDate.plus(2, ChronoUnit.DAYS)); System.out.println(period.getDays()); } }

java.time.Duration

Day보다 큰 단위로 표현이 가능. 월, 년

package org.smarttechie; import java.time.Duration; import java.time.LocalDateTime; import java.time.temporal.ChronoUnit; /** * This class demonstrates JAVA 8 data and time API * * @author Siva Prasad Rao Janapati * */ public class DurationDemonstration { /** * @param args */ public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); // Get the duration between two dates Duration duration = Duration.between(localDateTime, localDateTime.plus(2, ChronoUnit.DAYS)); System.out.println(duration.toDays()); } }

java.time.Year

윤년 여부도 알수 있는 Year 클래스

package org.smarttechie; import java.time.Year; /** * This class demonstrates JAVA 8 data and time API * @author Siva Prasad Rao Janapati * */ public class YearDemonstration { /** * @param args */ public static void main(String[] args) {   //Get year   Year year = Year.now();   System.out.println("Year ::" + year);   //know the year is leap year or not   System.out.println("Is year[" +year+"] leap year?"+ year.isLeap());  } }

참고 : Java 8 – New way to deal with Date and Time