How do I do a date add or substract?

public class CalendarAddExample
{
public static void main(String[] args)
{
Calendar cal = Calendar.getInstance();

System.out.println("Today : " + cal.getTime());

// Substract 30 days from the calendar
cal.add(Calendar.DATE, -30);
System.out.println("30 days ago: " + cal.getTime());

// Add 10 months to the calendar
cal.add(Calendar.MONTH, 10);
System.out.println("10 months later: " + cal.getTime());

// Substract 1 year from the calendar
cal.add(Calendar.YEAR, -1)
System.out.println("1 year ago: " + cal.getTime());
}
}