getting the difference between date in days in java

Possible Duplicate:
how to calculate difference between two dates using java

I'm trying something like this, where I'm trying to get the date from comboboxes

Calendar start = Calendar.getInstance();
Calendar end = Calendar.getInstance();  

int Sdate=Integer.parseInt(cmbSdate.getSelectedItem().toString());  
int Smonth=cmbSmonth.getSelectedIndex();
int Syear=Integer.parseInt(cmbSyear.getSelectedItem().toString());  

int Edate=Integer.parseInt(cmbEdate.getSelectedItem().toString());
int Emonth=cmbEmonth.getSelectedIndex();
int Eyear=Integer.parseInt(cmbEyear.getSelectedItem().toString());

start.set(Syear,Smonth,Sdate);  
end.set(Eyear,Emonth,Edate);

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
String startdate=dateFormat.format(start.getTime());  
String enddate=dateFormat.format(end.getTime());

I'm not able to subtract the end and start date How do I get the difference between the start date and end date??