3. Essential Java Classes 3. Date and Time презентация

3. Essential Java Classes 3. Date and Time

Date and Time Classes Date - represents a specific instant in time, with millisecond precision GregorianCalendar (concrete subclass of Calendar) – date and time manipulations SimpleDateFormat- formatting and parsing dates in a locale-sensitive manner Locale - represents a specific geographical, political, or cultural region SimpleTimeZone(concrete subclass of TimeZone) - represents a time zone for use with a Gregorian calendar

Class Date represents a specific instant in time, with millisecond precision new Date() returns current date and time Date saves the milliseconds since January 1, 1970, 00:00:00 Date does not localized. Most of it methods are deprecated. Calendar class allows to process dates

Some Date methods equals(Object obj) - compares dates after(Date date) - compares dates before(Date date) - compares dates getTime() – returns milliseconds since 01.01.1970 setTime() – sets date and time See http://docs.oracle.com/javase/7/docs/api/java/util/Date.html for details

Class Calendar Abstract class that provides methods for converting between a specific instant in time and a set of calendar fields Some calendar fields: YEAR, MONTH, DATE, DAY_OF_WEEK, HOUR_OF_DAY, MINUTE, SECOND, MILLISECOND

Calendar Methods Calendar rightNow = Calendar.getInstance(); - gets current date and time set(int field, int value) – sets calendar field value (then one of get (), getTime(), add(), roll() methods is needed) add(int field, int amount) – adds given amount to the field get(int field) – gets a given field value See http://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html for details

Class GregorianCalendar Concrete subclass of Calendar Provides the standard calendar system used by most of the world. Use GregorianCalendar for date and time manipulations See http://docs.oracle.com/javase/7/docs/api/java/util/GregorianCalendar.html for details

Calendar Examples Задание даты: GregorianCalendar calendar = new GregorianCalendar(2012, Calendar.May, 14); Добавление к дате двух недель: calendar.add(Calendar.WEEK_OF_YEAR, 2); Изменение полей даты: calendar.set(Calendar.DAY_OF_MONTH, 10); calendar.set(Calendar.MONTH, Calendar.SEPTEMBER); System.out.println(dtFrm.format(calendar.getTime()));

Date & Calendar Transformations Calendar c = Calendar.getInstance(); Date dt = new Date(); Calendar -> Date dt = c.getTime(); Date -> Calendar c.setTime(dt);

Class SimpleDateFormat is a concrete class for formatting and parsing dates in a locale-sensitive manner It allows for: formatting (date -> text) parsing (text -> date) See http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html for details

SimpleDateFormat Example SimpleDateFormat dtFrm = new SimpleDateFormat("dd.MM.yyyy"); Date start = new Date(); String txDate = dtFrm.format(start);

Class Locale represents a specific geographical, political, or cultural region Locale lc = new Locale(”uk”, ”UK”); Locale.getDefault() - gets the current value of the default locale See http://docs.oracle.com/javase/7/docs/api/java/util/Locale.html for details

Класс SimpleTimeZone A concrete subclass of TimeZone class that represents a time zone for use with a Gregorian calendar Can specify the year when the daylight saving time schedule starts or ends. See http://docs.oracle.com/javase/7/docs/api/java/util/SimpleTimeZone.html for details

SimpleDateFormat Localization SimpleDateFormat dtFrmL = new SimpleDateFormat("dd.MMMM.yyyy", Locale.ENGLISH); Date dt = new Date(); System.out.println("Locale.ENGLISH: " + dtFrmL.format(dt)); Locale.ENGLISH: 05.October.2013 Locale.GERMAN: 05.Oktober.2013 Locale.FRANCE: 05.octobre.2013 Locale.ITALIAN: 05.ottobre.2013 Locale("ua", "ua"): 05.October.2013 Locale("ru", "ru"): 05.Октябрь.2013

DateFormat Localization DateFormat dtFrmD = DateFormat.getDateInstance(DateFormat.DEFAULT, Locale.ENGLISH); System.out.println("Locale.ENGLISH: " + dtFrmD.format(dt)); Locale.ENGLISH: Oct 5, 2013 Locale.GERMAN: 05.10.2013 Locale.FRANCE: 5 oct. 2013 Locale.ITALIAN: 5-ott-2013 Locale("ua", "ua"): Saturday, October 5, 2013 Locale("ru", "ru"): 5 Октябрь 2013 г.

Date Localization http://docs.oracle.com/javase/tutorial/i18n/format/dateFormat.html

Exercise 3.3.1 Print the following: Current date Date in 6 weeks Date 4 month before Date in 45 days

Exercise 3.3.1 See 331DateActions project for the full text

Exercise 3.3.2. Create a static method that gets some date and returns next bank day

Exercise 3.3.2. See 332NextBankDay project for full text

Exercise 3.3.3. Create a method that gets two dates and returns number of days between these dates (general idea only!!!).