Trying to sort a linked HashMap by value

Question

letterFrequencies.entrySet().stream()
        .sorted(Map.Entry.comparingByValue().reversed())
        .collect(Collectors.toMap(Entry::getKey, Entry::getValue));

I'm currently using this to try but I get an error which says The method sorted(Comparator<? super Map.Entry<Character,Integer>>) in the type Stream<Map.Entry<Character,Integer>> is not applicable for the arguments (Comparator<Map.Entry<Object,Comparable<? super Comparable<? super V>>>>)

`Collectors.toMap` - oops. Even if you get your `Comparator` to work, dumping the result into a `HashMap` isn't going to yield anything useful. — Boris the Spider, Nov 26 '17 at 14:07

score 4 · Accepted Answer · answered Nov 26 '17 at 14:16

try something like:

LinkedHashMap<Character, Integer> resultSet = 
                   letterFrequencies.entrySet().stream()
                  .sorted(Map.Entry.<Character, Integer>comparingByValue().reversed())
                  .collect(Collectors.toMap(Entry::getKey, Entry::getValue, (e1, e2) -> e1, LinkedHashMap::new));

Also, as mentioned by Boris the Spider, dumping the result into a HashMap will not maintain insertion order hence the use of LinkedHashMap here.

Mahmoud Saeed · Answer 2 · 2017-11-26T14:31:20.337

0

You can pass the Comparator.reverseOrder() like this and collect into LinkedHashMap

letterFrequencies.entrySet().stream()
            .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
                    (v1, v2) -> v1, LinkedHashMap::new));

edited Nov 26 '17 at 14:31

answered Nov 26 '17 at 14:24

Mahmoud Saeed

16
3

You might want to change `comparingByKey` to `comparingByValue` – Shubhendu Pramanik Nov 26 '17 at 14:29

Trying to sort a linked HashMap by value

2 Answers2