How to Add or Subtract Weeks from a Date

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This code example shows how to add and remove weeks from a date using an instance of the Calendar class.
The method incrementWeeks takes two parameters, the Calendar object and the number of weeks to add.
The method decrementWeeks takes the same parameters and decrement the Calendar object with the number of weeks passed to it.
Note that the actuall call to the calendar is to the same method, add(), but when decrementing a negative value is passed.

The main method creates a Calendar object and print out the current date / time.
Then it instantiates a new Main object and call both methods with the calendar instance as parameter along with the number of weeks.

/**
*
* @author www.javadb.com
*/
public class Main {

    public void incrementWeeks(Calendar cal, int weeks) {

        cal.add(Calendar.WEEK_OF_YEAR, weeks);
        System.out.println("Date after increment: " + cal.getTime());
    }

    public void decrementWeeks(Calendar cal, int weeks) {

        cal.add(Calendar.WEEK_OF_YEAR, weeks);
        System.out.println("Date after decrement: " + cal.getTime());

    }
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        Calendar cal = Calendar.getInstance();
        System.out.println("Now : " + cal.getTime());
        Main main = new Main();
        main.incrementWeeks(cal, 1);
        main.decrementWeeks(cal, -2);
    }
}

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