How to find the Maximum value for specific key in List<TreeMap<Integer,Integer>>?

Question

Would you please help me to find the maximum value for each key from list of map: the list of map is like below:

[{47=96, 82=189, 100=231, 125=279, 158=322, 240=375},
 {47=125, 82=239, 100=285, 125=334, 158=378, 240=429},
 {47=119, 82=170, 100=182, 125=188, 158=188, 240=170}]

How to find max of value for each key? For example, the max value for the key 47 is 125, I need to find the max value of each key.

List<TreeMap<Integer, Integer>> listOfFreq = new ArrayList<>();

for (int thisFreq : frequencyList) {
    int max = listOfFreq.stream()
            .mapToInt(map -> map.getOrDefault(thisFreq, Integer.MIN_VALUE))
            .max().orElse(0);

Answer 1

You can flatten the entrySet of map using flatMap and collect as new map using Collectors.toMap with max value as the value of the key.

Map<Integer, Integer> res = 
    listOfFreq.stream()
              .flatMap(m -> m.entrySet().stream())
              .collect(Collectors.toMap(e -> e.getKey(), e -> e.getValue(), Integer::max));