Stream monstrosity

monster.java

private static Map<Integer, List<Integer>> makeFriendlists(List<Map<String, List<Integer>>> hashes) {
    Map<Integer, List<Integer>> result = new ConcurrentHashMap<>(); // concurrent put might happen in parallelstream
    // 1.: parallel stream all maps in list
    // 2.: parallel stream all entries in entrysets of hashes
    // 3.: for each entry in streamed hash, add it to the index list
    hashes.parallelStream().map(hashmap -> hashmap.entrySet().parallelStream())
            .forEach(entries -> entries.forEach(e -> {
                        List<Integer> friends = e.getValue();
                        for (Integer index : friends) {
                            if (result.containsKey(index)) {
                                List<Integer> indices = result.get(index);
                                // add each index in friends to indices, except index(which might occur more than once)
                                friends.stream().filter(i -> !i.equals(index)).forEach(indices::add);
                            } else {
                                List<Integer> indices = new ArrayList<>();
                                friends.stream().filter(i -> !i.equals(index)).forEach(indices::add);
                                result.put(index, indices);
                            }
                        }
                    }
            ));
    result.entrySet().parallelStream().map(Map.Entry::getValue).forEach(Collections::sort); // sort each friendlist
    return result;
}