using SimpleDateFormat or DateFormat class through
for e.g.
try{
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy"); // here set the pattern as you date in string was containing like date/month/year
Date d = sdf.parse("20/12/2011");
}catch(ParseException ex){
// handle parsing exception if date string was different from the pattern applying into the SimpleDateFormat contructor
}