Use the following to format your date:
new SimpleDateFormat("dd-MM-yyyy").format(comboCalendar.getDate())
As to your other question, you opened the wrong documentation.
getDate()
returns a java.util.Date
not a java.sql.Date
Correct documentation: http://docs.oracle.com/javase/7/docs/api/java/util/Date.html#toString%28%29