calculate iso week number in java

/**
 * @author lautturi.com
 * Java example:compute iso 8601 week number in java
 */
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.temporal.IsoFields;

import java.util.*;

public class Lautturi {

	public static void main(String[] args) {
		
		ZoneId zoneId = ZoneId.of ( "America/Montreal" );
		ZonedDateTime now = ZonedDateTime.now ( zoneId );
		int calendarYear = now.getYear();
		int weekYear = now.get ( IsoFields.WEEK_BASED_YEAR ); 
		int weekNumber = now.get ( IsoFields.WEEK_OF_WEEK_BASED_YEAR );

		System.out.println(weekNumber);

	}
}

output:

47