You could use the add
method and pass it a negative number. However, you could also write a simpler method that doesn't use the Calendar
class such as the following
public static void addDays(Date d, int days)
{
d.setTime( d.getTime() + (long)days*1000*60*60*24 );
}
This gets the timestamp value of the date (milliseconds since the epoch) and adds the proper number of milliseconds. You could pass a negative integer for the days parameter to do subtraction. This would be simpler than the "proper" calendar solution:
public static void addDays(Date d, int days)
{
Calendar c = Calendar.getInstance();
c.setTime(d);
c.add(Calendar.DATE, days);
d.setTime( c.getTime().getTime() );
}
Note that both of these solutions change the Date
object passed as a parameter rather than returning a completely new Date
. Either function could be easily changed to do it the other way if desired.