### Question:
Descriptives { public static FlatDataCollection mode(FlatDataCollection flatDataCollection) { AssociativeArray frequencies = frequencies(flatDataCollection); int maxCounter=0; FlatDataList modeList = new FlatDataList(); for(Map.Entry<Object, Object> entry : frequencies.entrySet()) { Object key = entry.getKey(); int count = ((Number)entry.getValue()).intValue(); if(maxCounter==count) { modeList.add(key); } else if(maxCounter<count) { maxCounter=count; modeList.clear(); modeList.add(key); } } return modeList.toFlatDataCollection(); }  static int count(Iterable it); static double sum(FlatDataCollection flatDataCollection); static double mean(FlatDataCollection flatDataCollection); static double meanSE(FlatDataCollection flatDataCollection); static double median(FlatDataCollection flatDataCollection); static double min(FlatDataCollection flatDataCollection); static double max(FlatDataCollection flatDataCollection); static double minAbsolute(FlatDataCollection flatDataCollection); static double maxAbsolute(FlatDataCollection flatDataCollection); static double range(FlatDataCollection flatDataCollection); static double geometricMean(FlatDataCollection flatDataCollection); static double harmonicMean(FlatDataCollection flatDataCollection); static double variance(FlatDataCollection flatDataCollection, boolean isSample); static double std(FlatDataCollection flatDataCollection, boolean isSample); static double cv(double std, double mean); static double moment(FlatDataCollection flatDataCollection, int r); static double moment(FlatDataCollection flatDataCollection, int r, double mean); static double kurtosis(FlatDataCollection flatDataCollection); static double kurtosisSE(FlatDataCollection flatDataCollection); static double skewness(FlatDataCollection flatDataCollection); static double skewnessSE(FlatDataCollection flatDataCollection); static AssociativeArray percentiles(FlatDataCollection flatDataCollection, int cutPoints); static AssociativeArray quartiles(FlatDataCollection flatDataCollection); static double covariance(TransposeDataList transposeDataList, boolean isSample); static double autocorrelation(FlatDataList flatDataList, int lags); static AssociativeArray frequencies(FlatDataCollection flatDataCollection); static FlatDataCollection mode(FlatDataCollection flatDataCollection); static void normalize(AssociativeArray associativeArray); static void normalizeExp(AssociativeArray associativeArray);  }### Answer:
@Test public void testMode() { logger.info("mode"); FlatDataCollection flatDataCollection = generateFlatDataCollection(); flatDataCollection.add(4.65); flatDataCollection.add(4.65); FlatDataCollection expResult = new FlatDataCollection(new ArrayList<>()); expResult.add(4.65); FlatDataCollection result = Descriptives.mode(flatDataCollection); assertEquals(expResult, result); }