3. Essential Java Classes. 3a. Date and Time in Java SE8 презентация

3. Essential Java Classes 3a. Date and Time in Java SE 8

Some New Date and Time Classes Package java.time LocalDate - a date without a time-zone in the ISO-8601 calendar system, such as 2007-12-03 LocalTime - a time without time-zone, such as 10:15:30 LocalDateTime - a date-time without a time-zone, such as 2007-12-03T10:15:30 Duration - a time-based amount of time, such as '34.5 seconds‘ Period - a date-based amount of time, such as '2 years, 3 months and 4 days‘

Some Date Enums java.time.DayOfWeek - a day-of-week, such as 'Tuesday‘ java.time.Month – a month-of-year, such as 'July‘ java.time.temporal.ChronoField – a standard set of fields provide field-based access to manipulate a date, time or date-time java.time.temporal.ChronoUnit – a standard set of date periods units

LocalDate Class Is an immutable date-time object that represents a date, often viewed as year-month-day Other date fields, such as day-of-year, day-of-week and week-of-year, can also be accessed This class does not store or represent a time or time-zone The ISO-8601 calendar system is the modern civil calendar system used today in most of the world. It is equivalent to the Gregorian calendar system The LocalDate class doesn’t have a public constructor

How to Create LocalDate now() - obtains the current date from the system clock in the default time-zone of(int year, int month, int dayOfMonth) -obtains an instance of LocalDate from a year, month and day of(int year, Month month, int dayOfMonth) - obtains an instance of LocalDate from a year, month and day

Date Formatting format(DateTimeFormatter  formatter) method formats the date using the specified formatter Formatter can be created as follows DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd.MM.yyyy"); Details are here: http://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html

Exercise Print current date, please

Print Current Date See 33a1CurrentDate project for the full text

LocalDate Comparison Methods compareTo(LocalDate other) - compares this date to another date equals(Object obj) - checks if this date is equal to another date isAfter(LocalDate other) - checks if this date is after the specified date isBefore(LocalDate other) - checks if this date is before the specified date

LocalDate Check/Length Methods isLeapYear() - checks if the year is a leap year lengthOfMonth() - returns the length of the month represented by this date lengthOfYear() - returns the length of the year represented by this date

LocalDate Plus Methods plusDays(long daysToAdd) - returns a copy of this LocalDate with the specified number of days added plusMonths(long monthsToAdd) - adds the specified period in months plusWeeks(long weeksToAdd) - adds the specified period in weeks plusYears(long yearsToAdd) – adds the specified period in years

Exercise Print the following: Current date Date in 6 weeks Date 4 month before Date in 45 days

Date Manipulations See 33a2DateManipulations project for the full text

Get Field of a Date (1 of 2) get(ChronoField field) - gets the value of the specified field from this date as an int ChronoField enum is a standard set of date fields: DAY_OF_MONTH, DAY_OF_WEEK, DAY_OF_YEAR, HOUR_OF_DAY, MONTH_OF_YEAR, YEAR, SECOND_OF_DAY etc. See for details: http://docs.oracle.com/javase/8/docs/api/java/time/temporal/ChronoField.html

Get Field of a Date (2 of 2) getDayOfWeek() - gets the day-of-week field, which is an enum DayOfWeek (MONDAY, TUESDAY, WEDNESDAY etc.) getDayOfMonth() - gets the day-of-month field getDayOfYear() - gets the day-of-year field getMonth() - gets the month-of-year field using the Month enum (JANUARY, FEBRUARY, etc.)

Exercise Create a method that gets some date and returns next bank day

Exercise See 33a3NextBankDate project for the full text

Some Other LocalDate Methods until(LocalDate endDate, ChronoUnit unit) - calculates the amount of time until endDate in terms of the specified unit withDayOfMonth(int dayOfMonth) - returns a copy of this date with the day-of-month altered withMonth(int month) - returns a copy of this date with the month-of-year altered withYear(int year) - returns a copy of this date with the year altered

Home Tasks How old are you in days and months? What day of week is your birthday? Calculate Orthodox Easter and Trinity dates for the current decade http://ru.wikipedia.org/wiki/%D0%90%D0%BB%D0%B3%D0%BE%D1%80%D0%B8%D1%82%D0%BC_%D0%93%D0%B0%D1%83%D1%81%D1%81%D0%B0_%D0%B2%D1%8B%D1%87%D0%B8%D1%81%D0%BB%D0%B5%D0%BD%D0%B8%D1%8F_%D0%B4%D0%B0%D1%82%D1%8B_%D0%9F%D0%B0%D1%81%D1%85%D0%B8

LocalDateTime Class LocalDateTime is an immutable date-time object that represents a date-time, often viewed as year-month-day-hour-minute-second Time is represented to nanosecond precision It is a description of the date, as used for birthdays, combined with the local time as seen on a wall clock It cannot represent an instant on the time-line without additional information such as an offset or time-zone

LocalDateTime Methods I now() compareTo(), equals(), isAfter(), isBefore() plusDays(), plusMonths(), plusWeeks(), plusYears() plusHours(), plusMinutes(), plusSeconds() get(ChronoField field), getDayOfWeek(), getDayOfMonth(), getDayOfYear(), getMonth() getHour(), getMinute(), getSecond()

LocalDateTime Methods II of(int year, int month, int dayOfMonth, int hour, int minute, int second) - obtains an instance of LocalDateTime from year, month, day, hour, minute and second, setting the nanosecond to zero format(DateTimeFormatter  formatter) - formats this date-time using the specified formatter

Print Current Date and Time public static void main(String[] args){ LocalDateTime currDateTime = LocalDateTime.now(); DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd.MM.yyyy HH:mm:ss"); String txt = currDateTime.format(formatter); System.out.println("Current date and time:" + txt); } See 33a6CurrentDateTime project for the full text

Converting from java.util.Date Convert java.util.Date to java.time.LocalDateTime: Date ts = new Date(); Instant instant = Instant.ofEpochMilli(ts.getTime()); LocalDateTime res = LocalDateTime.ofInstant(instant, ZoneId.systemDefault()); Convert java.util.Date to java.time.LocalDate: Date date = new Date(); Instant instant = Instant.ofEpochMilli(date.getTime()); LocalDate res = LocalDateTime.ofInstant(instant, ZoneId.systemDefault()).toLocalDate();

Converting to java.util.Date Convert java.time.LocalDateTime to java.util.Date: LocalDateTime ldt = LocalDateTime.now(); Instant instant = ldt.atZone(ZoneId.systemDefault()).toInstant(); Date res = Date.from(instant); Convert java.time.LocalDate to java.util.Date: LocalDate ld = LocalDate.now();; Instant instant = ld.atStartOfDay(). atZone(ZoneId.systemDefault()).toInstant(); Date res = Date.from(instant);

Manuals http://docs.oracle.com/javase/tutorial/datetime/index.html