How to check a day is in the current week in Java?

You definitely want to use the Calendar class: http://docs.oracle.com/javase/6/docs/api/java/util/Calendar.html

Here's one way to do it:

public static boolean isDateInCurrentWeek(Date date) {
  Calendar currentCalendar = Calendar.getInstance();
  int week = currentCalendar.get(Calendar.WEEK_OF_YEAR);
  int year = currentCalendar.get(Calendar.YEAR);
  Calendar targetCalendar = Calendar.getInstance();
  targetCalendar.setTime(date);
  int targetWeek = targetCalendar.get(Calendar.WEEK_OF_YEAR);
  int targetYear = targetCalendar.get(Calendar.YEAR);
  return week == targetWeek && year == targetYear;
}

Use the Calendar class to get the YEAR and WEEK_OF_YEAR fields and see if both are the same.

Note that the result will be different depending on the locale, since different cultures have different opinions about which day is the first day of the week.


tl;dr

What's a week? Sunday-Saturday? Monday-Sunday? An ISO 8601 week?

For a standard ISO 8601 week…

YearWeek.now( ZoneId.of( "America/Montreal" ) )
        .equals( 
            YearWeek.from( 
                LocalDate.of( 2017 , Month.JANUARY , 23 ) 
            ) 
        )

java.time

The modern approach uses the java.time classes that supplant the troublesome old date-time classes such as Date & Calendar.

In addition, the ThreeTen-Extra project provides a handy YearWeek class for our purposes here, assuming a standard ISO 8601 week is what you had in mind by the word "week". The documentation for that class summarized the definition of a standard week:

ISO-8601 defines the week as always starting with Monday. The first week is the week which contains the first Thursday of the calendar year. As such, the week-based-year used in this class does not align with the calendar year.

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.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "America/Montreal" );
YearWeek ywNow = YearWeek.now( z ) ;  // Get the current week for this specific time zone.

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

LocalDate ld = LocalDate.of( 2017 , Month.JANUARY , 23 ) ;  // Some date.

To see if a particular date is contained within the target YearWeek object’s dates, get the YearWeek of that date and compare by calling equals.

YearWeek ywThen = YearWeek.from( ld ) ;  // Determine year-week of some date.
Boolean isSameWeek = ywThen.equals( ywNow ) ;

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, & SimpleDateFormat.

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

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

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

  • Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
    • Java 9 brought some minor features and fixes.
  • Java SE 6 and Java SE 7
    • Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
  • Android
    • Later versions of Android (26+) bundle implementations of the java.time classes.
    • For earlier Android (<26), a process known as API desugaring brings a subset of the java.time functionality not originally built into Android.
      • If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….

Joda-Time

UPDATE: The Joda-Time project is now in maintenance mode, with the team advising migration to the java.time classes. Leaving this section intact for history.

Checking for ISO week is easy in Joda-Time 2.3.

// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.
// import org.joda.time.*;

DateTimeZone parisTimeZone = DateTimeZone.forID( "Europe/Paris" );
DateTime now = new DateTime( parisTimeZone );
DateTime yesterday = now.minusDays( 1 );
DateTime inThree = now.plusDays( 3 );
DateTime inFourteen = now.plusDays( 14 );

System.out.println( "Now: " + now + " is ISO week: " + now.weekOfWeekyear().get() );
System.out.println( "Same ISO week as yesterday ( " + yesterday + " week "+ yesterday.weekOfWeekyear().get() +" ): " + ( now.weekOfWeekyear().get() == yesterday.weekOfWeekyear().get() ) );
System.out.println( "Same ISO week as inThree ( " + inThree + " week "+ inThree.weekOfWeekyear().get() +" ): " + ( now.weekOfWeekyear().get() == inThree.weekOfWeekyear().get() ) );
System.out.println( "Same ISO week as inFourteen ( " + inFourteen + " week "+ inFourteen.weekOfWeekyear().get() +" ): " + ( now.weekOfWeekyear().get() == inFourteen.weekOfWeekyear().get() ) );

When run…

Now: 2013-12-12T06:32:49.020+01:00 is ISO week: 50
Same ISO week as yesterday ( 2013-12-11T06:32:49.020+01:00 week 50 ): true
Same ISO week as inThree ( 2013-12-15T06:32:49.020+01:00 week 50 ): true
Same ISO week as inFourteen ( 2013-12-26T06:32:49.020+01:00 week 52 ): false

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