Get Week and Year in Past Using LocalDate

I'm using the Java 8 time library to determine the previous weeks and year from today's date and then store those values in a map. I think I've figured out how to properly get the weeks, but I'm not entirely sure what the correct way is to get the year. Current code below:

int weeksLimit = 5; // this value is passed into the method, but just setting it here as an example
Map<Integer, Integer> yearWeeks = new HashMap<Integer, Integer>();
LocalDate ld = LocalDate.now();
WeekFields weekFields = WeekFields.of(DayOfWeek.SUNDAY, 4);
for (int i = weeksLimit; i > 0; i--) {
    LocalDate pastDate = ld.minusWeeks(i);
    yearWeeks.put(pastDate.getYear(), pastDate.get(weekFields.weekOfWeekBasedYear()));
}

I don't believe pastDate.getYear() is the correct usage. As the result I want is something along the lines of:

1/12/2020 - 1/18/2020 = Week 3, Year 2020
1/05/2020 - 1/11/2020 = Week 2, Year 2020
12/29/2019 - 1/04/2020 = Week 1, Year 2020
12/22/2019 - 12/28/2019 = Week 52, Year 2019

Could someone please help me figure out how to correctly get the year I want?

Solution

I can’t tell which is the right data structure for your purpose. A map with year as key and week as value won’t do for holding your example data. In your example year 2020 comes three times, but a given key can appear only once in a map. In the following example I am assuming a map that maps each week based year to a list of week numbers for that year.

    WeekFields weekFields = WeekFields.of(Locale.forLanguageTag("mt_MT"));

    int weeksLimit = 5; // this value is passed into the method, but just setting it here as an example

    LocalDate today = LocalDate.now(ZoneId.of("Europe/Malta"));
    Map<Integer, List<Integer>> yearWeeks = IntStream.rangeClosed(1, weeksLimit)
            .mapToObj(i -> today.minusWeeks(i))
            .collect(Collectors.groupingBy(ld -> ld.get(weekFields.weekBasedYear()),
                    Collectors.mapping(ld -> ld.get(weekFields.weekOfWeekBasedYear()),
                            Collectors.toList())));

    System.out.println(yearWeeks);

When I ran the snippet just now, the output was:

{2019=[52, 51], 2020=[3, 2, 1]}

I don’t expect to be there yet, but I am not putting more effort into this until I understand your requirements more clearly.