Try this:
String date = "2017-8-28";
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat dateFormatter = new SimpleDateFormat("MMMM dd, YYYY");
try {
Date startEntryDate = formatter.parse(date);
System.out.println(dateFormatter.format(startEntryDate));
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}