Sorting LinkedHashMap> by counting the occurrences in ArrayList problem

Question

I have:

ArrayList<String> miss;
LinkedHashMap<String, ArrayList<String>> map;

How can i sort "maps" by counting the occurrences in "miss"? For example:

miss => [3, 7]
maps => {1=[0, 3, 6], 4=[2, 3, 4], 6=[0, 3, 7], 11=[1, 3, 6], 17=[2, 6, 11]}

And i want to get:

maps => {6=[0, 3, 7], 1=[0, 3, 6], 4=[2, 3, 4], 11=[1, 3, 6], 17=[2, 6, 11]}

See https://stackoverflow.com/questions/2784514/sort-arraylist-of-custom-objects-by-property — tgdavies, Aug 30 '21 at 00:41
Does this answer your question? [Sort ArrayList of custom Objects by property](https://stackoverflow.com/questions/2784514/sort-arraylist-of-custom-objects-by-property) — Gabriel Donadel Dall'Agnol, Aug 31 '21 at 14:28

Nowhere Man · Accepted Answer · 2021-08-30T05:54:17.733

The following solution is based on using Stream API

Count the frequencies of elements from miss in each list value of maps and collect the frequency into some object (e.g. a list)
Sort the new object by the frequency in the reverse order and then by the key of initial map (note: the key may need to be converted into int to provide the expected output: 1, 4, 11; comparing the keys as String returns the order 1, 11, 4)
Build the resulting map using Collectors.toMap with LinkedHashMap::new supplier

List<String> miss = List.of("3", "7");
Map<String, List<String>> maps = Map.of(
     "1", List.of("0", "3", "6"),
     "4", List.of("2", "3", "4"),
     "6", List.of("0", "3", "7"),
    "11", List.of("1", "3", "6"),
    "17", List.of("2", "6", "11")
);

Map<String, List<String>> sorted = maps.entrySet()
    .stream()
    .map(e -> Arrays.asList(e, 
        e.getValue().stream()
            .mapToInt(i -> (int) miss.stream().filter(i::equals).count())
            .sum()
    ))
    .sorted(Comparator
        .<List>comparingInt(ee -> (int) ee.get(1)).reversed()
        .thenComparingInt(ee -> Integer.parseInt(((Map.Entry<String, List<String>>) ee.get(0)).getKey()))
    )
    .map(ee -> (Map.Entry<String, List<String>>) ee.get(0))
    .collect(Collectors.toMap(
        Map.Entry::getKey,
        Map.Entry::getValue,
        (v1, v2) -> v1,
        LinkedHashMap::new
    ));

System.out.println(sorted);

Output:

{6=[0, 3, 7], 1=[0, 3, 6], 4=[2, 3, 4], 11=[1, 3, 6], 17=[2, 6, 11]}

Sorting LinkedHashMap> by counting the occurrences in ArrayList problem

1 Answers1