public void calculate()

in oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/meter/function/avg/AvgHistogramPercentileFunction.java [196:271]
70 lines of code
13 McCabe index (conditional complexity)

    public void calculate() {
        if (!isCalculated) {
            final Set<String> keys = summation.keys();
            for (String key : keys) {
                long value = 0;
                if (count.get(key) != 0) {
                    value = summation.get(key) / count.get(key);
                    if (value == 0L && summation.get(key) > 0L) {
                        value = 1;
                    }
                }
                dataset.put(key, value);
            }
            dataset.keys().stream()
                   .map(key -> {
                       DataLabel dataLabel = new DataLabel();
                       if (key.contains(":")) {
                           int index = key.lastIndexOf(":");
                           dataLabel.put(key.substring(0, index));
                           return Tuple.of(dataLabel, key);
                       } else {
                           return Tuple.of(dataLabel, key);
                       }
                   })
                   .collect(groupingBy(Tuple2::_1, mapping(Tuple2::_2, Collector.of(
                       DataTable::new,
                       (dt, key) -> {
                           String v;
                           if (key.contains(":")) {
                               int index = key.lastIndexOf(":");
                               v = key.substring(index + 1);
                           } else {
                               v = key;
                           }
                           dt.put(v, dataset.get(key));
                       },
                       DataTable::append
                   ))))
                   .forEach((labels, subDataset) -> {
                       long total;
                       total = subDataset.sumOfValues();

                    int[] roofs = new int[ranks.size()];
                    for (int i = 0; i < ranks.size(); i++) {
                        roofs[i] = Math.round(total * ranks.get(i) * 1.0f / 100);
                    }

                    int count = 0;
                    final List<String> sortedKeys = subDataset.sortedKeys(Comparator.comparingLong(Long::parseLong));

                    int loopIndex = 0;

                    for (String key : sortedKeys) {
                        final Long value = subDataset.get(key);

                        count += value;
                        for (int rankIdx = loopIndex; rankIdx < roofs.length; rankIdx++) {
                            int roof = roofs[rankIdx];

                            if (count >= roof) {
                                if (labels.isEmpty()) {
                                    labels.put(PERCENTILE_LABEL_NAME, String.valueOf(ranks.get(rankIdx)));
                                    percentileValues.put(labels, Long.parseLong(key));
                                } else {
                                    labels.put(PERCENTILE_LABEL_NAME, String.valueOf(ranks.get(rankIdx)));
                                    percentileValues.put(labels, Long.parseLong(key));
                                }
                                loopIndex++;
                            } else {
                                break;
                            }
                        }
                    }
                });
        }
    }