Find max number of elements in list using stream

findMaxNumberOfElementsInList.java

// find max number of elements in list like below example
// ex) in beloew list, elements '3' has max number of elements(max count how many exist in list)
//     List<Integer> arr = Arrays.asList(1, 2, 3, 4, 5, 4, 3, 2, 1, 3, 4);
//     elements '3' and '4' have frequency 4 in this list. 
//     but '3' is smaller than '4', So elements '3' is max number of elements. 

// Complete the migratoryBirds function below.
 static int migratoryBirds(List<Integer> arr) {
 //return arr.stream().filter(i -> Collections.frequency(arr, i) > 1).max(Integer::compare).get();
   // get Frequency each elements -> return Map
   Map<Integer, Long> cntList = arr.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
   // compare using reduce, What has most bigger frequency(getValue) and smaller self than others(getKey) 
   return cntList.entrySet().stream().reduce((x,y)-> (x.getValue()>=y.getValue())?(x.getKey()<=y.getKey()?x:y):y).get().getKey();
 }