TopItems { public static long[] getTopUsers(int howMany, LongPrimitiveIterator allUserIDs, IDRescorer rescorer, Estimator<Long> estimator) throws TasteException { Queue<SimilarUser> topUsers = new PriorityQueue<>(howMany + 1, Collections.reverseOrder()); boolean full = false; double lowestTopValue = Double.NEGATIVE_INFINITY; while (allUserIDs.hasNext()) { long userID = allUserIDs.next(); if (rescorer != null && rescorer.isFiltered(userID)) { continue; } double similarity; try { similarity = estimator.estimate(userID); } catch (NoSuchUserException nsue) { continue; } double rescoredSimilarity = rescorer == null ? similarity : rescorer.rescore(userID, similarity); if (!Double.isNaN(rescoredSimilarity) && (!full || rescoredSimilarity > lowestTopValue)) { topUsers.add(new SimilarUser(userID, rescoredSimilarity)); if (full) { topUsers.poll(); } else if (topUsers.size() > howMany) { full = true; topUsers.poll(); } lowestTopValue = topUsers.peek().getSimilarity(); } } int size = topUsers.size(); if (size == 0) { return NO_IDS; } List<SimilarUser> sorted = new ArrayList<>(size); sorted.addAll(topUsers); Collections.sort(sorted); long[] result = new long[size]; int i = 0; for (SimilarUser similarUser : sorted) { result[i++] = similarUser.getUserID(); } return result; } private  TopItems(); static List<RecommendedItem> getTopItems(int howMany,
                                                  LongPrimitiveIterator possibleItemIDs,
                                                  IDRescorer rescorer,
                                                  Estimator<Long> estimator); static long[] getTopUsers(int howMany,
                                   LongPrimitiveIterator allUserIDs,
                                   IDRescorer rescorer,
                                   Estimator<Long> estimator); static List<GenericItemSimilarity.ItemItemSimilarity> getTopItemItemSimilarities(
    int howMany, Iterator<GenericItemSimilarity.ItemItemSimilarity> allSimilarities); static List<GenericUserSimilarity.UserUserSimilarity> getTopUserUserSimilarities(
    int howMany, Iterator<GenericUserSimilarity.UserUserSimilarity> allSimilarities);  }
@Test public void testTopUsers() throws Exception { long[] ids = new long[100]; for (int i = 0; i < 100; i++) { ids[i] = i; } LongPrimitiveIterator possibleItemIds = new LongPrimitiveArrayIterator(ids); TopItems.Estimator<Long> estimator = new TopItems.Estimator<Long>() { @Override public double estimate(Long thing) { return thing; } }; long[] topItems = TopItems.getTopUsers(10, possibleItemIds, null, estimator); int gold = 99; for (long topItem : topItems) { assertEquals(gold--, topItem); } }