Locale and Date Classes

1
Locale and Date Classes

• Locale
• Date
• DateFormat
• Gregorian Calendar

2
Locale Class

• A Locale object represents a specific
  geographical, political, or cultural region. An
  operation that requires a Locale to perform its
  task is called locale-sensitive and uses the
  Locale to tailor information for the user.
• The Locale Class contains a number of static
  constants to identify common locales. Because
  they are static, you can use them with the Class
  name (no instantiating a Locale object needed).
• example Locale.CANADA
• See the Sun Web Site documentation about the
  Locale class for a list of static constants you
  can use to represent countries/locales.
• http//java.sun.com/j2se/1.4/docs/api/index.html

3
GregorianCalendar Class

• GregorianCalendar is a concrete subclass of
  Calendar and provides the standard calendar used
  by most of the world.
• The standard (Gregorian) calendar has 2 eras, BC
  and AD.
• This Class contains static Format Fields that
  make it easy to get the information you want
  about a date/time. There are static Constants,
  too.
• The GregorianCalendar Class also contains useful
  methods such as isLeapYear()

4
GregorianCalendar Fields

• static Format Fields
• AM_PM - 0 (AM) or 1 (PM)
• DAY_OF_WEEK - 1 to 7
• DAY_OF_YEAR - 1 to 366
• MONTH - 0 to 11
• DAY_OF_MONTH - 1 to 31
• WEEK_OF_MONTH - 1 to 6
• HOUR_OF_DAY - 0 to 23
• HOUR - 1 to 12
• MINUTE - 0 to 59
• SECOND - 0 to 59
• MILLISECOND - 0 to 999
• YEAR - current year (e.g. 2002)

5
GregorianCalendar Constants

• an example of static Constants
• AM
• APRIL
• AUGUST
• DECEMBER
• FEBRUARY
• FRIDAY
• JANUARY
• JULY
• JUNE
• MARCH
• MAY
• MONDAY
• Etc.

6

• //new calendar object using system date and time
• GregorianCalander cal new GregorianCalendar( )
  
• //get the day of the week (1SUNDAY, etc)
• int day cal.get(cal.DAY_OF_WEEK)
• //create a String of Date and Time
• String dtg cal.get(cal.YEAR)
• (cal.get(cal.MONTH) 1)
• cal.get(cal.DAY_OF_MONTH)
• cal.get(cal.HOUR_OF_DAY)
• cal.get(cal.MINUTE)
• cal.get(cal.SECOND)

7

• //Instantiate new calendar object using a
  specific date
• GregorianCalander cal
• new GregorianCalendar( 2002,
• 
  GregorianCalendar.AUGUST,
• 10 )
• //Use this to create a Date object with this same
  date
• Date myBirthday cal.getTime( )

8
The Date Classes

• Date Class
• defines an instant in time to the nearest
  millisecond measured from January 1, 1970 GMT
• DateFormat Class
• abstract class used to create meaningful String
  representations of Date objects

9
Date

• Constructors ( only two )
• Date( )
• Creates an object based on the current time from
  your computer clock
• Date( long time )
• Creates an object based on the time value
• time value must be in milliseconds since 1/1/70
  000000
• Examples
• Instantiate a new Date using the current system
  date and time
• Date today new Date( )
• Instantiate a new Date using a specific date
• GregorianCalendar cal new GregorianCalendar(
  1962,
• 
  GregorianCalendar.AUGUST, 01 )
• Date myBirthDay cal.getTime( )

10
DateFormat

• Abstract class that provides format and locale
  templates for producing Dates and Times in
  readable String representations.
• Formats
• SHORT - numeric representation such as 01/01/01
  or 220
• MEDIUM - 10-Jan-01
• LONG - January 10, 2001
• FULL - comprehensive representation such as
• Wednesday, January 10, 2001 or 22014 GMT

11
DateFormat static methods

• Default formatters
• getDateInstance( ),
• getTimeInstance( ),
• getDateTimeInstance( )
• Specify formatter
• getDateInstance(int dateStyle),
• getTimeInstance(int timeStyle),
  getDateTimeInstance(int dateStyle, int timeStyle)

12
Using Dates

• //create a Date Object
• Date today new Date( ) //system date and time
• //get a DateFormat ( use Date/Time Instance
  default )
• DateFormat fmtDateFormat.getDateTimeInstance()
• // pass the Date through it
• String defaultFmt fmt.format(today)
• ____________________________________________
• //get a DateFormat, specifying the style. . .
• fmt DateFormat.getDateTimeInstance(DateFormat.FU
  LL)
• String fullFmt fmt.format(today)

13
Lab

• Date Formatting example on page 458-459 of text
  book.

14
Project 5

• Create a class called Friend that contains
  String first name and last name attributes, and a
  Date birthdate attribute. Include an overloaded
  constructor that takes the first name, last name,
  birthyear, birthmonth, and birthday as parameters
  and sets the private attributes of your Friend.
  Include setters and getters for first and last
  name and the Date birthdate attribute.
• Write a driver program that creates a Vector of 5
  of your friends initialize their names and
  birthday information, then display each friends
  birthday in the following Date and Locale
  formats (see example program on page 458-459)
• FULL, LONG, SHORT, MEDIUM and US, UK, GERMANY,
  FRANCE
• Hint Go to http//java.sun.com/j2se/1.4/api/inde
  x.html for help with using the Utility classes,
  their constructors, formatters, iterators, etc