You need to change pattern which shows to you desired data format:
DateFormat dateFormat = new SimpleDateFormat("dd");
instead of
DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
UPDATE:
Java 1.8 has updated data and time API.
Here is snippet of code which I checked:
LocalDate lastAprilDay = LocalDate.of(2014, Month.APRIL, 30);
System.out.println("last april day: " + lastAprilDay);
LocalDate firstMay = lastAprilDay.plusDays(1);
System.out.println("should be first may day: " + firstMay);
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd");
String formatDate = formatter.format(firstMay);
System.out.println("formatted date: " + formatDate);
Output:
last april day: 2014-04-30
should be first may day: 2014-05-01
formatted date: 01
For more info see Java documentations to this classes: