How do I add hours, minutes or seconds to a date in Java?

import java.util.Calendar;

public class DateAddHour {
    public static void main(String[] args) {
        //
        // Gets a calendar using the default time zone and locale. The
        // Calendar returned is based on the current time in the default
        // time zone with the default locale.
        //
        Calendar calendar = Calendar.getInstance();
        System.out.println("Original = " + calendar.getTime());

        //
        // Substract 2 hour from the current time
        //
        calendar.add(Calendar.HOUR, -2);

        //
        // Add 30 minutes to the calendar time
        //
        calendar.add(Calendar.MINUTE, 30);

        //
        // Add 300 seconds to the calendar time
        //
        calendar.add(Calendar.SECOND, 300);

        System.out.println("Updated  = " + calendar.getTime());
    }
}