If you only want to get the max number of days in a month you can do the following.
// Set day to one, add 1 month and subtract a day
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.DAY_OF_MONTH, 1);
cal.add(Calendar.MONTH, 1);
cal.add(Calendar.DAY_OF_MONTH, -1);
return cal.get(Calendar.DAY_OF_MONTH);
If you actually want to print every day then you can just set the day of month to 1 and keep adding a day in a loop until the month changes.
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.DAY_OF_MONTH, 1);
int myMonth=cal.get(Calendar.MONTH);
while (myMonth==cal.get(Calendar.MONTH)) {
System.out.print(cal.getTime());
cal.add(Calendar.DAY_OF_MONTH, 1);
}