Если вы используете Java 8, вы можете использовать java.time API. Вот так:
int addWeek = 0;
if(startDate.get(WeekFields.ISO.weekOfYear()) < endDate.get(WeekFields.ISO.weekOfYear())){
addWeek = 1;
}
long weeks = WEEKS.between(startDate, endDate) + addWeek;//Get the number of weeks in your case (52)
List<Integer> numberWeeks = new ArrayList<>();
if (weeks >= 0) {
int week = 0;
do {
//Get the number of week
int weekNumber = startDate.plusWeeks(week).get(WeekFields.ISO.weekOfYear());
numberWeeks.add(weekNumber);
week++;
} while (week <= weeks);
}
Ideone demo
[34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52,
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34]
Обратите внимание, что вы получаете номера обеих недель за оба года, недели 2018 [34-52]
, а затем недели 2019 [1-33]