Here is an example that determines the date on coming sunday from the specified date.

import java.util.*;
import java.text.*;

class  GetDateExample
{
    public static void main(String[] args) throws Exception
    {
    String str_date="24-08-2012";
    SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy");
    Date date = (Date)formatter.parse(str_date);
    Calendar cal=Calendar.getInstance();
    cal.setTime(date);
    while(cal.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY){
        cal.add(Calendar.DAY_OF_WEEK, 1);
    }
    System.out.println("Date on coming sunday is " + formatter.format(cal.getTime()));
    }
}