Stats.java

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.*;
import java.util.function.Predicate;
import java.util.stream.Stream;

import static java.util.stream.Collectors.*;

public class Stats {
    public static void main(String[] args) throws IOException {
        List<Data> list = Files.lines(Paths.get("file"))
                .map(s -> s.substring(1, s.length()-1).split(","))
                .map(arr -> new Data(Integer.parseInt(arr[0]), arr[1]))
                .collect(toList());

        System.out.println(list);
        System.out.println(ids(list, "a", i -> i < 3));

        Map<String, IntSummaryStatistics> stats = list.stream()
                .flatMap(d -> d.getMap().entrySet().stream())
                .collect(toMap(Map.Entry::getKey,
                                e -> e.getValue().stream().mapToInt(i -> i).summaryStatistics(),
                                (i1, i2) -> {i1.combine(i2); return i1;}));

        stats.forEach((k, v) -> System.out.println(k + " => " + v));

    }

    public static Set<Integer> ids(List<Data> list, String id, Predicate<Integer> predicate) {
        return list.stream()
                .filter(d -> d.getMap().containsKey(id))
                .filter(d -> d.getMap().get(id).stream().anyMatch(predicate))
                .map(d -> d.getId())
                .collect(toSet());
    }
}

class Data {
    private int id;
    private Map<String, List<Integer>> map;

    public Data(int id, String datas) {
        this.id = id;
        this.map = new HashMap<>();

        for(String s : datas.substring(1, datas.length()-1).split("\\|")) {
            String[] splitted = s.split(":");
            this.map.merge(splitted[0], Arrays.asList(Integer.parseInt(splitted[1])), (l1, l2) -> Stream.concat(l1.stream(), l2.stream()).collect(toList()));
        }
    }

    public int getId() {
        return this.id;
    }

    public Map<String, List<Integer>> getMap() {
        return this.map;
    }

    @Override
    public String toString() {
        return "Data{" +
                "id=" + id +
                ", map=" + map +
                '}';
    }
}