Second Monday of Current year

Question

I need to calculate second monday of current year in one of program. a method in java which tells what is the date on second monday of current year using Gregorian Calendar. Please suggest.

Answer 1

You could have written something like this

int year = 2016;
Calendar cal = Calendar.getInstance();
cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
cal.set(Calendar.DAY_OF_WEEK_IN_MONTH, 2);
cal.set(Calendar.MONTH, Calendar.JANUARY);
cal.set(Calendar.YEAR, year);
return cal.get(Calendar.DATE);

Answer 2

Set calendar to the first day of the month jan.

Retrieve its day of the week

Calculate the date of the first Monday of the month.

Add 7 days using calendar.add() method. You will get the second Monday.

Answer 3

tl;dr

java.util.GregorianCalendar.from( 
    LocalDate.now( ZoneId.of( "America/Montreal" ) ) 
             .with( TemporalAdjusters.firstDayOfYear() )
             .with( TemporalAdjusters.dayOfWeekInMonth( 2 , DayOfWeek.MONDAY ) )
             .atStartOfDay( ZoneId.of( "America/Montreal" ) )
)

Avoid legacy date-time classes

The GregorianCalendar class is now legacy, supplanted by the java.time classes, specifically ZonedDateTime. Avoid the old legacy date-time classes as they are poorly-designed, confusing, and troublesome.

LocalDate

For a date-only value, use LocalDate. The LocalDate class represents a date-only value without time-of-day and without time zone.

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

ZoneId z = ZoneId.of( "America/Montreal" );
LocalDate today = LocalDate.now( z );

TemporalAdjuster

The TemporalAdjuster interface provides for classes to manipulate date-time values. The TemporalAdjusters (note plural 's') class provides several handy implementations.

We an adjuster to get the first day of the current year, and another to get the second Monday of that month.

LocalDate firstOfYear = today.with( TemporalAdjusters.firstDayOfYear() );
LocalDate secondMondayOfYear = firstOfYear.with( TemporalAdjuster.dayOfWeekInMonth( 2 , DayOfWeek.MONDAY ) );

GregorianCalendar

If you really need a GregorianCalendar you can convert by calling new methods added to the old classes. I assume you want the time-of-day set to the first moment of the day. That first moment is not always 00:00:00 so let java.time determine that time-of-day.

ZonedDateTime zdt = secondMondayOfYear.atStartOfDay( z );
GregorianCalendar gc = java.util.GregorianCalendar.from( zdt );

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About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, .Calendar, & java.text.SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to java.time.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

• Java SE 8 and SE 9 and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.