How to find elements in List having more occurrences in Java?

Question

Java

There is a list of strings:

List<String> s = Arrays.asList("a", "a", "a", "b", "c");

To find the most frequently occurring letter using stririm:

// получим количество повторений по каждой букве (a = 3, b = 1, c = 1)
Map<String, Long> map= s.stream()
                    .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

// Из этого списка уже получаем букву с самым большим количеством повторений (это буква "а")
Optional<String> mostCommon = map.entrySet().stream()
            .max(Map.Entry.comparingByValue())
            .map(Map.Entry::getKey);

And how to get several letters, which will have the same maximum number of repetitions :

// a = 3 и b = 3
List<String> s = Arrays.asList("a", "a", "a", "b", "b", "b", "b", "c");

Tried something like this, but it doesn't work:

Set<Srring> mostWidelyUsed = map.entrySet().stream()
                    .map(v -> Collections.max(v, Map.Entry.comparingByValue()))
                    .collect(Collectors.toSet());

Answer 1

var s = Arrays.asList("a", "a", "a", "b", "b", "b", "c");

        var map = s.stream()
                .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

        var max = map.entrySet().stream()
                .max(Map.Entry.comparingByValue())
                .map(Map.Entry::getValue)
                .orElse(0L);

        var result = map.entrySet().stream()
                .filter(e -> e.getValue().equals(max))
                .map(Map.Entry::getKey)
                .collect(Collectors.toList());  // [a, b]